mhchem (7apr15)

git-svn-id: svn://tug.org/texlive/trunk@36738 c570f23f-e606-0410-a88d-b1316a301751

4 files changed, 1965 insertions, 1918 deletions

diff --git a/Master/texmf-dist/doc/latex/mhchem/README b/Master/texmf-dist/doc/latex/mhchem/README
index 0fc068570e5..d68a8b1ffd4 100644
--- a/Master/texmf-dist/doc/latex/mhchem/README
+++ b/Master/texmf-dist/doc/latex/mhchem/README
@@ -1,7 +1,7 @@
-The mhchem Bundle 2015-03-13
+The mhchem Bundle 2015-04-07
 
 containing
-- mhchem v3.21
+- mhchem v4.00
 - hpstatement v1.01
 - rsphrase v3.11
 
diff --git a/Master/texmf-dist/doc/latex/mhchem/mhchem.pdf b/Master/texmf-dist/doc/latex/mhchem/mhchem.pdf
index 261398f5f3a..a9ef2485772 100644
--- a/Master/texmf-dist/doc/latex/mhchem/mhchem.pdf
+++ b/Master/texmf-dist/doc/latex/mhchem/mhchem.pdf
diff --git a/Master/texmf-dist/doc/latex/mhchem/mhchem.tex b/Master/texmf-dist/doc/latex/mhchem/mhchem.tex
index e881716ec98..660487a951f 100644
--- a/Master/texmf-dist/doc/latex/mhchem/mhchem.tex
+++ b/Master/texmf-dist/doc/latex/mhchem/mhchem.tex
@@ -27,23 +27,24 @@
 % This work consists of all files listed in manifest.txt.
 %
 %
-\documentclass[a4paper,notitlepage]{scrreprt}
-\usepackage{fontspec}
-\usepackage[danish,french,ngerman,italian,spanish,UKenglish]{babel}
-\usepackage{mathpazo}% math font
-\setmainfont[Mapping=tex-text]{TeX Gyre Pagella}% URWPalladioL
-  % http://www.ctan.org/tex-archive/fonts/tex-gyre/fonts
+\documentclass[a4paper,notitlepage,parskip=half]{scrreprt}
+\usepackage[T1]{fontenc}
+\usepackage[utf8]{inputenc}
+\usepackage[danish,french,ngerman,spanish,italian,UKenglish]{babel}
+\usepackage{tgpagella}% URW Palladio
 \addtokomafont{disposition}{\rmfamily}
 \linespread{1.1}
-\setmonofont[Mapping=tex-text,Scale=MatchLowercase]{Source Code Pro}
-  % http://sourceforge.net/projects/sourcecodepro.adobe/
+\usepackage{mathpazo}% math font
+\usepackage[scale=0.9]{sourcecodepro}
+\usepackage{AlegreyaSans}
 \usepackage[bookmarks,bookmarksopen,pdfstartview=FitH]{hyperref}
 \usepackage[alwaysadjust]{paralist}
 \usepackage{ragged2e}
 \usepackage{fvrb-ex}% example environments
-\usepackage{color}
+\usepackage{xcolor}
+\usepackage{nameref}
 
-\usepackage[version=3]{mhchem}
+\usepackage[version=4]{mhchem}
 \usepackage{hpstatement}
 \usepackage{rsphrase}
 \usepackage{tikz}
@@ -54,7 +55,10 @@
 \newcommand\fromversion[1]{\marginpar{{\scriptsize version$\geq$#1}}}
 \newenvironment{annotation}{\bgroup\footnotesize}{\par\egroup}
 
-
+\definecolor{mhchem}{HTML}{A33E00}
+\makeatletter
+\def\mhchem@hook@beforeCe{\color{mhchem}}
+\makeatother
 
 \begin{document}
 
@@ -62,7 +66,7 @@
   The mhchem Bundle\\[0.3em]
   \Large\textmd{%
     Documentation for the Packages\\
-    mhchem v3.21,\\% check
+    mhchem v4.00,\\% check
     hpstatement v1.01 and\\
     rsphrase v3.11}%
 }
@@ -71,7 +75,7 @@
   mhchem\makebox[0pt][l]{\textcolor{white}{NOSPAM}}@MartinHensel\makebox[1pt][l]{\textcolor{white}{.}}.de%
 }
 \date{%
-  2015-03-13% check
+  2015-04-07% check
 }
 \maketitle
 
@@ -80,11 +84,11 @@
 \begin{abstract}
   \noindent
   The \textbf{mhchem} package provides commands for typesetting chemical molecular formulae and equations.
-  \medskip
 
-  \noindent The \textbf{hpstatement} package provides commands for the official hazard statements and precautionary statements (H and P statements) that are used to label chemicals.
   \medskip
+  \noindent The \textbf{hpstatement} package provides commands for the official hazard statements and precautionary statements (H and P statements) that are used to label chemicals.
 
+  \medskip
   \noindent
   The \textbf{rsphrase} package provides commands for the official Risk and Safety (R and S) Phrases that are used to label chemicals.
 \end{abstract}
@@ -97,457 +101,408 @@
 
 
 \clearpage
-
 \chapter{The mhchem Package}
 
+
 \section{Work in Progress}
 
-The mhchem package is still work in progress. Admittedly, very slow progress with large breaks in between, but still progressing. Version 4 will be a major rewrite of the code with some new features and slight syntax changes (this will be the reason for the new number). While I try to support the old syntaxes via the \verb|version| option, please note that slight changes in spacing (and therefore changed line breaks and page breaks) can occur from release to release.
+Even after years, the mhchem package is still work in progress. I try to never invalidate valid, old syntaxes (via the \verb|version| option). However, slight changes in spacing (and therefore changed line breaks and page breaks) can occur from release to release.
 
+\textbf{The version 4 syntax is subject to change if I find a serious flaw, for a couple of months after first release.} After that, it will be stable and  syntax incompatible changes would only occur in a future version 5.
 
+\section{Preamble}
 
-\section{Why this package?}
+In order to use all of mhchem's features, request it in your document's preamble with the command
 
-\noindent
-For typesetting a single chemical formula from time to time, one can use \LaTeX's math mode, manually setting the letters in an upright font.
+{\color{mhchem}\Large\verb|\usepackage|{\ttfamily\bfseries [version=4]}\verb|{mhchem}|}
+\marginpar{\Large !}
 
-\begin{addmargin}[4em]{0em}
-\begin{SideBySideExample}[xrightmargin=3cm]
-  $\frac{1}{2}\,\mathrm{H}_2\mathrm{O}$
-\end{SideBySideExample}
-\end{addmargin}
+\begin{annotation}
+What about the \verb|version=4|? During development, I became aware that additional functionality could not be added without changing the user-interface slightly. But what about backward compatibility? I could, of course freeze mhchem and publish an mhchem2 package. However, I decided to use a parameter in order to switch to the new interface. One can use \verb|version=4| for the most-recent version of mhchem, but \verb|version=2| to \verb|version=1| are still there for existing documents that use an old user-interface of mhchem. Those old documents should still produce the same results. However, spacing might differ slightly.
+\end{annotation}
 
-\noindent
-In addition, one has to care about the height of subscripts, as the following example shows. The 2 and the 7 are not aligned properly.
+mhchem needs a couple of other packages. For instance, expl3, amsmath and calc.
 
-\begin{addmargin}[4em]{0em}
-\begin{SideBySideExample}[xrightmargin=3cm]
-  $3\,\mathrm{Cr}_2\mathrm{O}_7^{2-}$
-\end{SideBySideExample}
-\end{addmargin}
 
-\noindent
-So one would have to write
+\section{Chemical Equations}
 
-\begin{addmargin}[4em]{0em}
-\begin{SideBySideExample}[xrightmargin=3cm]
-  $3\,\mathrm{Cr}_2^{\strut}\mathrm{O}_7^{2-}$
+\begin{SideBySideExample}[xrightmargin=6cm]
+  \ce{CO2 + C -> 2 CO}
 \end{SideBySideExample}
-\end{addmargin}
 
-\noindent
-But this in turn changes the line height. That has to be compensated. And so on and so forth. At the end, you have to write long commands and may be lost eventually, when a formula should appear inside a section header with a different font.
+\begin{SideBySideExample}[xrightmargin=6cm]
+  \ce{Hg^2+ ->[I-] HgI2 
+            ->[I-] [Hg^{II}I4]^2-}
+\end{SideBySideExample}
 
-\bigskip
 
-\noindent
-mhchem is here to assist you. To mention a few of its features:
-\smallskip
 
-\begin{compactitem}
-  \item Adaptation to the surrounding environment\\
-	If used inside normal text or a section header, the formula is displayed using the current text font. If used inside a math environment, the current math font is used in the appropriate size.
+\section{Chemical Formulae}
 
-  \item More natural input\\
-  I am convinced that (when expecting a chemical formula) it is easier to read and write \verb|H3PO4| than \verb|H_3PO_4|. The latter is grouped wrongly according to the Gestalt rules. Furthermore, you can copy formulas from text e-mails and even Word documents and save a lot of time as you do not have to insert underscores. (One could argue that this is inconsistend with math mode and could lead to confusions. I believe, however that \verb|O2| and \verb|x_2| are sufficiently distinct concepts.)
+\begin{SideBySideExample}[xrightmargin=2.5cm]
+  \ce{H2O}
+\end{SideBySideExample}
 
-  \item Easy input of amount numbers\\
-  with automatic spacing; easy input of fractions
+\begin{SideBySideExample}[xrightmargin=2.5cm]
+  \ce{Sb2O3}
+\end{SideBySideExample}
 
-  \item Fine typographic corrections\\
-  fine correction of the height of subscripts and superscripts; right-aligned left-side subscripts and superscripts
-\end{compactitem}
 
-\noindent
-\ldots{} and a lot more. But let me end the ad block here and see for yourself how easy it can be to typeset chemical formulae.
+This works in text mode (even in headings) and in math mode. (For PDF bookmarks you might have to specify a text-only version.)
 
+{
+\let\sffamilyorig\sffamily
+\def\sffamily{\color{mhchem}\sffamilyorig}
+\begin{SideBySideExample}[xrightmargin=5cm]
+  \sffamily\itshape
+  This is text with \ce{H2O} and $\ce{H2O}$.
+\end{SideBySideExample}
+}
 
-\section{Preamble}
+For how to fine-tune the font usage, see \nameref{sec:FineTuning}.
 
-\noindent
-In order to use all of mhchem's features, request it in your document's preamble with the command
 
-\smallskip
+\section{Charges}
 
-{\Large\verb|\usepackage|{\ttfamily\bfseries [version=3]}\verb|{mhchem}|}
-\marginpar{\Large !}
+\begin{SideBySideExample}[xrightmargin=2.5cm]
+  \ce{H+}
+\end{SideBySideExample}
 
-\medskip
+\begin{SideBySideExample}[xrightmargin=2.5cm]
+  \ce{CrO4^2-}
+\end{SideBySideExample}
 
-\begin{annotation}
-\noindent
-What about the \verb|version=3|? During development, I became aware that additional functionality could not be added without changing the user-interface slightly. But what about backward compatibility? I could, of course freeze mhchem and publish an mhchem2 package. However, I decided to use a parameter in order to switch to the new interface. One can use \verb|version=3| for the most-recent version of mhchem, but \verb|version=2| and \verb|version=1| and \verb|0| are still there for existing documents that use an old user-interface of mhchem. Those old documents should still produce the same results. However, spacing might differ slightly.
-\end{annotation}
+\begin{SideBySideExample}[xrightmargin=2.5cm]
+  \ce{[AgCl2]-}
+\end{SideBySideExample}
 
-\medskip
+\begin{SideBySideExample}[xrightmargin=2.5cm]
+  \ce{Y^99+}
+\end{SideBySideExample}
 
-\noindent
-mhchem needs a couple of other packages. For instance, expl3, amsmath and calc.
+\begin{SideBySideExample}[xrightmargin=2.5cm]
+  \ce{Y^{99+}}
+\end{SideBySideExample}
 
+This will work in text mode and math mode. For text, the en-dash will be used as a minus sign.
 
 
-\section{Basics}
+\section{Stoichiometric Numbers}
 
-\noindent
 \begin{SideBySideExample}[xrightmargin=2.5cm]
-  \ce{H2O}
+  \ce{2H2O}
 \end{SideBySideExample}
 
-\medskip
 \begin{SideBySideExample}[xrightmargin=2.5cm]
-  \ce{Sb2O3}
+  \ce{2 H2O}
 \end{SideBySideExample}
 
-\medskip
 \begin{SideBySideExample}[xrightmargin=2.5cm]
-  \ce{H+}
+  \ce{0.5H2O}
 \end{SideBySideExample}
 
-\medskip
 \begin{SideBySideExample}[xrightmargin=2.5cm]
-  \ce{CrO4^2-}
+  \ce{1/2H2O}
 \end{SideBySideExample}
 
-\medskip
 \begin{SideBySideExample}[xrightmargin=2.5cm]
-  \ce{[AgCl2]-}
+  \ce{(1/2)H2O} % IUPAC Green Book
 \end{SideBySideExample}
 
-\medskip
+This works in text mode and math mode. (The fraction line always comes from math mode and might appear too small when using bold text fonts.)
+
+
+\section{Isotopes}
+
 \begin{SideBySideExample}[xrightmargin=2.5cm]
-  \ce{(NH4)2S}
+  \ce{^{227}_{90}Th+}
 \end{SideBySideExample}
 
-\medskip
 \begin{SideBySideExample}[xrightmargin=2.5cm]
-  \ce{Y^99+}
+  \ce{^227_90Th+}
 \end{SideBySideExample}
-\fromversion{3.21}
 
-\medskip
 \begin{SideBySideExample}[xrightmargin=2.5cm]
-  \ce{Y^{99+}}
+  \ce{H{}^3HO}
 \end{SideBySideExample}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=2.5cm]
-  \ce{H2(aq)} % IUPAC
+Of course, this works in text mode and math mode.
+
+
+\section{Greek Letters}
+
+Just write \macro{alpha} etc.
+
+\begin{SideBySideExample}[xrightmargin=4cm]
+  \ce{\mu-Cl}
 \end{SideBySideExample}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=2.5cm]
-  \ce{CO3^2-{}_{(aq)}} % not according to IUPAC
+\begin{SideBySideExample}[xrightmargin=4cm]
+  \ce{[Pt(\eta^2-C2H4)Cl3]-}
 \end{SideBySideExample}
 
+This works in text mode and math mode. For the time being, the math font will be used. But for the next release, an improvement is currently in the making.
 
-\subsection{Amounts}
 
-Place amounts directly in front of a formula. A small space will be inserted
-automatically.
+\section{Parenthesis, Brackets, Braces}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=2cm]
-  \ce{2H2O}
-\end{SideBySideExample}
+Use parenthesis \verb|( )| and brackets \verb|[ ]| normally. Write braces as \verb|\{ \}|.
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=2cm]
-  \ce{0.5H2O}
+\begin{SideBySideExample}[xrightmargin=4cm]
+  \ce{(NH4)2S}
 \end{SideBySideExample}
-\fromversion{3.13}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=2cm]
-  \ce{1/2H2O}
+\begin{SideBySideExample}[xrightmargin=4cm]
+  \ce{[\{(X2)3\}2]^3+}
 \end{SideBySideExample}
 
+Small parenthesis etc. work in both, text mode and math mode. Large parenthesis etc. are a math-mode only feature.
 
-\subsection{Isotopes}
+Both, \macro{left} and \macro{right} macros, need to be in the same math environment, so you might have to put \macro{ce} into \verb|$| into \macro{ce}, but that's fine.
 
-\begin{SideBySideExample}[xrightmargin=2cm]
-  \ce{^{227}_{90}Th+}
+$\displaystyle\ce{CH4 + 2 $\left( \ce{O2 + 79/21 N2} \right)$}$\par
+{\raggedleft\verb|\[\ce{CH4 + 2 $\left( \ce{O2 + 79/21 N2} \right)$}\]|\par}
+
+
+\section{States of Aggregation}
+
+\begin{SideBySideExample}[xrightmargin=4cm]
+  \ce{H2(aq)} % IUPAC recommendation
 \end{SideBySideExample}
 
+\begin{SideBySideExample}[xrightmargin=4cm]
+  \ce{CO3^2-{}_{(aq)}} % not according to IUPAC
+\end{SideBySideExample}
+
+\begin{SideBySideExample}[xrightmargin=4cm]
+  \ce{NaOH(aq,$\infty$)}
+\end{SideBySideExample}
+
+This works in text mode and math mode.
 
-\subsection{Special Symbols}
+
+\section{Addition Compounds}
 
 \begin{SideBySideExample}[xrightmargin=5cm]
   \ce{KCr(SO4)2*12H2O}
 \end{SideBySideExample}
 
-\medskip
 \begin{SideBySideExample}[xrightmargin=5cm]
   \ce{KCr(SO4)2.12H2O}
 \end{SideBySideExample}
 
-\medskip
-\noindent\ce{[Cd\{SC(NH2)2\}2].[Cr(SCN)4(NH3)2]2}\par
-\noindent\hspace{5cm}\verb|\ce{[Cd\{SC(NH2)2\}2].[Cr(SCN)4(NH3)2]2}|
-
-\medskip
 \begin{SideBySideExample}[xrightmargin=5cm]
-  $\ce{RNO2^{-.}}$, \ce{RNO2^{-.}}
+  \ce{KCr(SO4)2 * 12 H2O}
 \end{SideBySideExample}
-\fromversion{2}
 
+The centered dot is taken from math font.
 
-\subsection{Bonds}
 
-\noindent
-Horizontal \fromversion{2} bonds can be set using the characters \verb|-|, \verb|=| and \verb|#| (single, double, triple bond) inside a formula (a \verb|-| at the end of a formula yields a negative charge).
+\section{Unpaired Electrons, Radical Dots}
 
-\medskip
+\begin{SideBySideExample}[xrightmargin=3cm]
+  \ce{OCO^{.-}}
+\end{SideBySideExample}
 
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{C6H5-CHO}
+\begin{SideBySideExample}[xrightmargin=3cm]
+  \ce{NO^{(2.)-}}
 \end{SideBySideExample}
 
-\medskip
+This superscript-only feature works in text mode and math mode. A math bullet is used.
 
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{X=Y#Z}
+
+\section{Bonds}
+
+\begin{SideBySideExample}[xrightmargin=3cm]
+  \ce{C6H5-CHO}
 \end{SideBySideExample}
 
-\medskip
+\begin{SideBySideExample}[xrightmargin=3cm]
+  \ce{A-B=C#D}
+\end{SideBySideExample}
 
-\noindent
-Different books visualise bonds in extremely different ways. Here, the  minus sign from the math font is used to display the bonds (even in text mode).  The bonds are vertically aligned on the math axis. For most math fonts, this  is slightly lower than half the height of a capital letter.
+\begin{SideBySideExample}[xrightmargin=3cm]
+  \sffamily\bfseries
+  \ce{A-B=C#D}
+\end{SideBySideExample}
 
-\medskip
+mhchem tries to differentiate if \verb|\ce{-}| should be a bond, a charge or even a hyphen.
 
-\noindent
-The \macro{bond} \fromversion{3} command allows you to typeset special bonds.
+The \verb|#| bond might not work if you pass it through other commands. In this case, use \verb|\bond{3}| instead.
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
+\begin{SideBySideExample}[xrightmargin=3cm]
   \ce{A\bond{-}B\bond{=}C\bond{#}D}
 \end{SideBySideExample}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
+\begin{SideBySideExample}[xrightmargin=3cm]
   \ce{A\bond{1}B\bond{2}C\bond{3}D}
 \end{SideBySideExample}
-\fromversion{3.15}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
+\mhchemoptions{minus-text-sidebearing-left=0.1em,minus-text-sidebearing-right=0.18em}
+\begin{SideBySideExample}[xrightmargin=3cm]
   \ce{A\bond{~}B\bond{~-}C}
 \end{SideBySideExample}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
+\begin{SideBySideExample}[xrightmargin=3cm]
   \ce{A\bond{~--}B\bond{~=}C\bond{-~-}D}
 \end{SideBySideExample}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
+\begin{SideBySideExample}[xrightmargin=3cm]
   \ce{A\bond{...}B\bond{....}C}
 \end{SideBySideExample}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
+\begin{SideBySideExample}[xrightmargin=3cm]
   \ce{A\bond{->}B\bond{<-}C}
 \end{SideBySideExample}
 
-\medskip
-
-\noindent
-Please be aware, that the dashed bonds use the \macro{scalebox} macro internally, which may not be visualised correctly by some DVI viewers. If you switch to  another math font, the sidebearing of the minus sign may vary, which would cause  the dashed bonds to align badly (in \verb|\bond{~--}|, for instance). In that  case, you may want to adjust the layout by using the command  \verb|\mhchemoptions{minus-sidebearing-left=0.06em,| \verb|minus-sidebearing-right=0.11em}| with the appropriate values.
-
+Text mode: Line-based bonds are based on the text-font's en-dash. For all the others, math glyphs are used.
 
-\subsection{Fonts}
+Math mode: Bonds are based on the math-font minus sign.  All bonds are vertically aligned on the math axis. For most math fonts, this  is slightly lower than half the height of a capital letter.
 
-A few words about fonts. LaTeX distinguishes between text fonts and math fonts. In general, the math fonts have much more glyphs: alphas, nabla operators and all that kind of suff. Ideally, the math font looks very similar to the text font and that is why many LaTeX users do not know about the two kinds of fonts. However, the distinction is important for the use of mhchem.
+If you switch to another font, the sidebearing of the minus sign may vary, which would cause the dashed bonds to align badly. In that  case, adjust the alignment by using the following command with slightly changed values. Use \verb|\mhchemoptions{minus-text-sidebearing-left=0.10em,| \verb|minus-text-sidebearing-right=0.16em}| for text font adjustment and \verb|\mhchemoptions{minus-math-sidebearing-left=0.06em,| \verb|minus-math-sidebearing-right=0.11em}| for math font.
 
-\medskip
 
-\noindent
-When you are in a math environment (e.g. opened and closed with a \$), \macro{ce}'s content will be set in an upright math font. (Remember: all variables---like $V$ for volume---are set using an italic font, physical units and chemical elements are set using an upright font.)
+\section{Using Math, Variables}
 
-\medskip
+You can `half-escape' to math by using \verb|$...$|. Remember, that the math font might not always match with the text font (e.\,g. in headings).
 
-\begin{SideBySideExample}[xrightmargin=5cm]
-  $V_{\ce{H2O}}$
+\begin{SideBySideExample}[xrightmargin=4cm]
+  $\ce{NaOH(aq,$\infty$)}$\\
+  \sffamily\bfseries
+  \ce{NaOH(aq,$\infty$)}
 \end{SideBySideExample}
 
-\medskip
-
-\noindent
-When used in text mode, \macro{ce} adapts to the current text font. You could simply write a formula in one of your section titles. It would be set with the correct font, no matter where is appears (section title, header, table of contents, references, \dots).
-
-\medskip
-
-\begin{SideBySideExample}[xrightmargin=5cm]
-  £\sffamily\textbf
-  This is text with \ce{H2O} and $\ce{H2O}$.
+\begin{SideBySideExample}[xrightmargin=4cm]
+  $\ce{Fe(CN)_{$\frac{6}{2}$}}$\\
+  \sffamily\bfseries
+  \ce{Fe(CN)_{$\frac{6}{2}$}}
 \end{SideBySideExample}
 
-\medskip
+When `half-escaped', mhchem tries to recognize common patterns and still use the correct font.
 
-\begin{SideBySideExample}[xrightmargin=5cm]
-  £\sffamily
-  \ce{Ce^{IV}}, $\ce{Ce^{IV}}$
+\begin{SideBySideExample}[xrightmargin=4cm]
+  $\ce{Fe^$n$+}$ \sffamily\bfseries \ce{Fe^$n$+} 
 \end{SideBySideExample}
-\fromversion{2.04}
-
-\medskip
-
-\noindent
-There are some special cases. A negative charge in text mode is replaced with a dash (--, normally input as \verb|--|), because a text minus sign is  often too short (compare $\text{Cl}^{\text{-}}$ and \ce{Cl-}). All `operators' in equations, e.g. `+' and reaction arrows, are  taken from the math font.
 
+You can prevent this recognition by `fully escaping' to math with \verb|${...}$|.
 
-\subsection{Using Math}
+\begin{SideBySideExample}[xrightmargin=4cm]
+  $\ce{Fe^${n}$+}$ \sffamily\bfseries \ce{Fe^${n}$+}
+\end{SideBySideExample}
 
-To
-\fromversion{3.05}
-use math commands inside \macro{ce}, these commands can be enclosed by \verb|$|. Please be aware that a math font will be used for these parts, i.\,e., this might not look good in text that differs from math, like headlines.
+The same common patterns are also recognized at many places when used without \verb|$...$|.
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{$\mu\hyphen$Cl}
+\begin{SideBySideExample}[xrightmargin=4cm]
+  $\ce{Fe^n+}$ \sffamily\bfseries \ce{Fe^$n$+}
 \end{SideBySideExample}
-\fromversion{3.05}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{Fe(CN)_{$\frac{6}{2}$}}
+\begin{SideBySideExample}[xrightmargin=4cm]
+  $\ce{NO_$x$}$ \sffamily\bfseries \ce{NO_$x$}
 \end{SideBySideExample}
 
-\medskip
-\noindent\ce{$x\,$ Na(NH4)HPO4 ->[\Delta] (NaPO3)_{$x$} + $x\,$ NH3 ^ + $x\,$ H2O}\par
-\noindent\hspace{5cm}\verb|\ce{$x\,$ Na(NH4)HPO4 ->[\Delta]|\par
-\noindent\hspace{5cm}\verb|  (NaPO3)_{$x$} +|\par
-\noindent\hspace{5cm}\verb|  $x\,$ NH3 ^ + $x\,$ H2O}|
-
+$\ce{x Na(NH4)HPO4 ->[\Delta] (NaPO3)_x + x NH3 ^ + x H2O}$\par
+{\raggedleft\verb|$\ce{x Na(NH4)HPO4 ->[\Delta] (NaPO3)_x + x NH3 ^ + x H2O}$|\par}
 
 
-\section{Formulae}
+\section{Italic Text}
 
-\subsection{Reaction Arrows}
+With the same mechanism, you can switch to italic font.
 
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{CO2 + C -> 2CO}
+\begin{SideBySideExample}[xrightmargin=4cm]
+  $\ce{$cis${-}[PtCl2(NH3)2]}$\\
+  \sffamily\bfseries
+  \ce{$cis${-}[PtCl2(NH3)2]}
 \end{SideBySideExample}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{CO2 + C <- 2CO}
-\end{SideBySideExample}
+Spaces will be ignored. Use a \verb|~| when you need to typeset a space.
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{CO2 + C <=> 2CO}
-\end{SideBySideExample}
+This works for the text mode as long as you use latin characters. It also works for math font. Remember, however, that italic math is normally reserved for variables and $cis$ mostly means `product of $c$, $i$, and $s$'.
 
-\medskip
-%\begin{SideBySideExample}[xrightmargin=5cm]
-%  \ce{H+ + OH- <=>> H2O}
-%\end{SideBySideExample}
-\noindent
-\makebox[5cm][l]{\ce{H+ + OH- <=>> H2O}}\verb|\ce{H+ + OH- <=>> H2O}|
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{$A$ <-> $A'$}
-\end{SideBySideExample}
+\section{Escape Parsing, Upright Text}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{CO2 + C ->[\alpha] 2CO}
-\end{SideBySideExample}
+If you want to escape parsing, for instance for a simple hyphen, use \verb|{...}|.
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{CO2 + C ->[\alpha][\beta] 2CO}
+\begin{SideBySideExample}[xrightmargin=4cm]
+  \ce{{(+)}_589{-}[Co(en)3]Cl3}
 \end{SideBySideExample}
 
-\medskip
 
-\noindent
-The content above and below reaction arrows is set in math font. When you want to put descriptive text there, use the \macro{text} command. Or, as a shortcut, you could type a `T' between reaction arrow and opening bracket.
+\section{Reaction Arrows}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{CO2 + C ->[\text{above}] 2CO}
-\end{SideBySideExample}
+\makebox[3cm][l]{\ce{A -> B}}\verb|\ce{A -> B}|\\
+\makebox[3cm][l]{\ce{A <- B}}\verb|\ce{A <- B}|\\
+\makebox[3cm][l]{\ce{A <-> B}}\verb|\ce{A <-> B}|\\
+\makebox[3cm][l]{\ce{A <--> B}}\verb|\ce{A <--> B}|\\
+\makebox[3cm][l]{\ce{A <=>> B}}\verb|\ce{A <=>> B}|\\
+\makebox[3cm][l]{\ce{A <<=> B}}\verb|\ce{A <<=> B}|
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{CO2 + C
-    ->[\text{above}][\text{below}] 2CO}
-\end{SideBySideExample}
+The arrow arguments use the same syntax as the \macro{ce} command.
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{CO2 + C ->T[above][below] 2CO}
+\begin{SideBySideExample}[xrightmargin=3cm]
+  \ce{A ->[H2O] B}
 \end{SideBySideExample}
 
-\medskip
-
-\noindent
-Similarly, there is a shortcut for using \macro{ce} with reaction arrows:
-
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{$A$ ->[\ce{+H2O}] $B$}
+\begin{SideBySideExample}[xrightmargin=3cm]
+  \ce{A ->[{text above}][{text below}] B}
 \end{SideBySideExample}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{$A$ ->C[+H2O] $B$}
+\begin{SideBySideExample}[xrightmargin=3cm]
+  \ce{A ->[$x_i$] B}
 \end{SideBySideExample}
 
+For how to can change the layout of the arrows, see \nameref{sec:FineTuning}.
 
-\subsection{Precipitate and Gas}
 
-\noindent Use \verb|v| or \verb|(v)| for precipitate (arrow down) and \verb|^| or \verb|(^)| for gas (arrow up), all of them separated by spaces.
+\section{Precipitate and Gas}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=7cm]
+\begin{SideBySideExample}[xrightmargin=6cm]
   \ce{SO4^2- + Ba^2+ -> BaSO4 v}
 \end{SideBySideExample}
 
-
-\subsection{Large Parenthesis}
-
-Both, \verb|\left| and \verb|\right| macros, need to be in the same math environment, so you might have to put \verb|$| into \verb|\ce| into \verb|$| into \verb|\ce|, but that's fine.
-
-\begin{Example}[xrightmargin=15cm]
-  \[\ce{CH4 + 2 $\left( \ce{O2 + $\frac{79}{21}\,$ N2} \right)$}\]
-\end{Example}
-\fromversion{3.18}
+\begin{SideBySideExample}[xrightmargin=6cm]
+  \ce{A v B (v) -> B ^ B (^)}
+\end{SideBySideExample}
 
 
-\subsection{Further Examples}
+\section{Further Examples}
 
 \begin{Example}[xrightmargin=15cm]
   \ce{Zn^2+
-    <=>[\ce{+ 2OH-}][\ce{+ 2H+}]
+    <=>[+ 2OH-][+ 2H+]
     $\underset{\text{amphoteres Hydroxid}}{\ce{Zn(OH)2 v}}$
-    <=>C[+2OH-][{+ 2H+}]
+    <=>[+ 2OH-][+ 2H+]
     $\underset{\text{Hydroxozikat}}{\ce{[Zn(OH)4]^2-}}$
   }
 \end{Example}
-\fromversion{3.05}
-
-\bigskip
 
 \begin{Example}[xrightmargin=5cm]
   $K = \frac{[\ce{Hg^2+}][\ce{Hg}]}{[\ce{Hg2^2+}]}$
 \end{Example}
 
-\medskip
 \begin{Example}[xrightmargin=5cm]
-  \ce{Hg^2+ ->[\ce{I-}]
+  \ce{Hg^2+ ->[I-]
     $\underset{\mathrm{red}}{\ce{HgI2}}$
-    ->C[I-]
+    ->[I-]
     $\underset{\mathrm{red}}{\ce{[Hg^{II}I4]^2-}}$
   }
 \end{Example}
-\fromversion{3.05}
 
 
-\section[Equation Environments]{Equation Environments\fromversion{2}}
+
+\section{Equation Environments}
+
+\subsection{Aligning Equations}
+
+You can use \verb|&| and \verb|\\| inside \macro{ce} to align equations.
+
+\begin{SideBySideExample}[xrightmargin=5cm]
+  \begin{align*}
+    \ce{RNO2 &<=>[+e] RNO2^{-.} \\
+         RNO2^{-.} &<=>[+e] RNO2^2-}
+  \end{align*}
+\end{SideBySideExample}
+
 
 \subsection{Own Equation Command}
 
@@ -559,21 +514,17 @@ When you use equation environments containing a \macro{ce} very often, you might
     {\begin{equation*}\ce{#1}\end{equation*}}
 \end{Verbatim}
 
-\noindent
 and then use them as follows.
 
+\newcommand\reaction[1]{\begin{equation}\ce{#1}\end{equation}}
+\newcommand\reactionnonumber[1]%
+  {\begin{equation*}\ce{#1}\end{equation*}}
 \begin{SideBySideExample}[xrightmargin=5cm]
-  £\newcommand\reaction[1]{\begin{equation}\ce{#1}\end{equation}}
-  £\newcommand\reactionnonumber[1]%
-  £  {\begin{equation*}\ce{#1}\end{equation*}}
   \reaction{CO2 + C}
   \reactionnonumber{CO2 + C}
 \end{SideBySideExample}
 
-\bigskip
-
-\noindent
-The advanced \LaTeX\ user could replace the two definitions by
+The advanced \LaTeX\ user could replace the two definitions by one
 \begin{Verbatim}
   \makeatletter
     \newcommand\reaction@[1]{\begin{equation}\ce{#1}\end{equation}}
@@ -582,26 +533,25 @@ The advanced \LaTeX\ user could replace the two definitions by
     \newcommand\reaction{\@ifstar{\reaction@nonumber}{\reaction@}}
   \makeatother
 \end{Verbatim}
+
 and then write
+
+\makeatletter
+  \newcommand\reaction@[1]{\begin{equation}\ce{#1}\end{equation}}
+  \newcommand\reaction@nonumber[1]%
+    {\begin{equation*}\ce{#1}\end{equation*}}
+  \renewcommand\reaction{\@ifstar{\reaction@nonumber}{\reaction@}}
+\makeatother
 \begin{SideBySideExample}[xrightmargin=5cm]
-  £\makeatletter
-  £  \newcommand\reaction@[1]{\begin{equation}\ce{#1}\end{equation}}
-  £  \newcommand\reaction@nonumber[1]%
-  £    {\begin{equation*}\ce{#1}\end{equation*}}
-  £  \newcommand\reaction{\@ifstar{\reaction@nonumber}{\reaction@}}
-  £\makeatother
   \reaction{CO2 + C}
   \reaction*{CO2 + C}
 \end{SideBySideExample}
 
-\smallskip
-
-\noindent
 for the same result.
 
 \minisec{}
 
-So far, so good. All reactions will be labelled exactly as all the equations. A few people asked for a diffent set of numbers for equations and reactions. One could use this code:
+So far, so good. All reactions will be labelled exactly as all the equations. A few people asked for a \emph{different} set of numbers for equations and reactions. One could use this code:
 
 \begin{Verbatim}
   \makeatletter
@@ -626,30 +576,29 @@ So far, so good. All reactions will be labelled exactly as all the equations. A
   \makeatother
 \end{Verbatim}
 
-\noindent
 With that, all reactions will be labelled independently of the equations.
 
+\makeatletter
+\newcounter{reaction}
+%%% >> for article <<
+%\renewcommand\thereaction{C\,\arabic{reaction}}
+%%% << for article <<
+%%% >> for report and book >>
+\renewcommand\thereaction{C\,\thechapter.\arabic{reaction}}
+\@addtoreset{reaction}{chapter}
+%%% << for report and book <<
+\newcommand\reactiontag%
+  {\refstepcounter{reaction}\tag{\thereaction}}
+\renewcommand\reaction@[2][]%
+  {\begin{equation}\ce{#2}%
+  \ifx\@empty#1\@empty\else\label{#1}\fi%
+  \reactiontag\end{equation}}
+\renewcommand\reaction@nonumber[1]%
+  {\begin{equation*}\ce{#1}\end{equation*}}
+\renewcommand\reaction%
+  {\@ifstar{\reaction@nonumber}{\reaction@}}
+\makeatother
 \begin{SideBySideExample}[xrightmargin=6.5cm]
-  £\makeatletter
-  £\newcounter{reaction}
-  £%%% >> for article <<
-  £%\renewcommand\thereaction{C\,\arabic{reaction}}
-  £%%% << for article <<
-  £%%% >> for report and book >>
-  £\renewcommand\thereaction{C\,\thechapter.\arabic{reaction}}
-  £\@addtoreset{reaction}{chapter}
-  £%%% << for report and book <<
-  £\newcommand\reactiontag%
-  £  {\refstepcounter{reaction}\tag{\thereaction}}
-  £\newcommand\reaction@[2][]%
-  £  {\begin{equation}\ce{#2}%
-  £  \ifx\@empty#1\@empty\else\label{#1}\fi%
-  £  \reactiontag\end{equation}}
-  £\newcommand\reaction@nonumber[1]%
-  £  {\begin{equation*}\ce{#1}\end{equation*}}
-  £\newcommand\reaction%
-  £  {\@ifstar{\reaction@nonumber}{\reaction@}}
-  £\makeatother
   \begin{equation}a+b\end{equation}
   \reaction{CO2 + C}
   \reaction*{CO2 + C}
@@ -658,107 +607,89 @@ With that, all reactions will be labelled independently of the equations.
 \end{SideBySideExample}
 
 
-\subsection{Aligning Equations}
-
-When using equation environments, you can use the \macro{cee} command. The advantage is, that \macro{cee} can take the \verb|&| and \verb|\\| macros as input and passes them on to the surrounding environment.
-
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \begin{align*}
-    \cee{RNO2 &<=>C[+e] RNO2^{-.} \\
-         RNO2^{-.} &<=>C[+e] RNO2^2-}
-  \end{align*}
-\end{SideBySideExample}
-
-
 
-\section[Splitting the \macro{ce} command]{Splitting the \macro{ce} command\fromversion{3.21}}
+\section{Splitting the \macro{ce} command}
 
-\noindent
 As mentioned before, you can use  \verb|$| to switch to math mode inside \macro{ce}. But maybe, you want to `escape' to outside of \macro{ce}.
 
 
 \subsection{Comma Example}
 
-\noindent
 Assume, you are getting tired of typing
 
-\medskip
 \begin{SideBySideExample}[xrightmargin=4cm]
   \ce{N2}, \ce{O2}, \ce{CO2}
 \end{SideBySideExample}
 
-\medskip
-
-\noindent
 Then you could define your own command that splits at commas (plus space).
 
-\medskip
 \begin{SideBySideExample}[xrightmargin=4cm]
   \newcommand*\cec[1]{\cesplit{{\,\ }{\0}}{#1}}
   \cec{N2, O2, CO2}
 \end{SideBySideExample}
 
-\medskip
-
-\noindent
-\macro{cesplit} takes two parameters. The first one is a list of search-and-replace pairs, the second parameter is the chemistry string as you would put into \macro{ce}. The search-and-replace list uses the syntax of \verb|l3regex|. As a rule of thumb, precede every non-letter with a backslash. You can replace it with some other text, or use \verb|\0| to retain the match. If you want to replace with a macro, write \verb|\c{macroname}|. For furhter details, refer to the \verb|l3regex| manual.
-
-\medskip
-
-\noindent
-You could even re-define \macro{ce} with \verb|\newcommand*\ce{\cesplit{...}{#1}}|.
+You could re-define \macro{ce} with \verb|\newcommand*\ce{\cesplit{...}{#1}}|, if you do not like to create a new name.
 
 
 \subsection{Layer Stacks}
 
-\noindent
 Another example shows how physicists can use mhchem to write layer stacks.
 
 \medskip
 \begin{SideBySideExample}[xrightmargin=4cm]
   \newcommand*\stackslash{\text{/}\allowbreak}
-  \newcommand*\stackdash{\text{-}\allowbreak}
+  \newcommand*\stackhyphen{\text{-}\allowbreak}
   \newcommand\stack[1]{%
     \cesplit{%
       {\/}{\c{stackslash}}%
-      {-}{\c{stackdash}}%
+      {-}{\c{stackhyphen}}%
     }{#1}%
   }
   \ldots\ structure of
   \stack{Co-Fe-B/HfO2/Co-Fe-B} is resp\ldots
 \end{SideBySideExample}
 
-\medskip
 
-\noindent
-By the way, mhchem's \macro{cee} command is similarly defined.
+\subsection{The Details}
+
+\macro{cesplit} takes two parameters. The first one is a list of search-and-replace pairs, the second parameter is the chemistry string as you would put into \macro{ce}. The search-and-replace list uses the syntax of \verb|l3regex|. As a rule of thumb, precede every non-letter with a backslash. You can replace it with some other text, or use \verb|\0| to retain the match. If you want to replace with a macro, write \verb|\c{macroname}|. For further details, refer to the \verb|l3regex| manual.
+
+Do not nest \macro{cesplit} commands.
 
+The result of \macro{cesplit} does \emph{not} have the feature to use \verb|&| and \verb|\\| as you might to want to deal with them differently. \macro{ce} is itself defined by \macro{cesplit} (which, technically speaking, does not split \macro{ce}, but an internal command). As \macro{ce} is defined by
 
+\begin{Verbatim}
+    \cesplit % spaced added for readability
+      {
+        { \c{\\}(\[.*?\])? } { \0 }
+        { \& } { \0 }
+      }
+      {#1}
+\end{Verbatim}
 
-\section{Fine Tuning}
+you could add these rules to you own \macro{cesplit} definition.
 
-In this section, several option switches will be explained. You can use them in the form
 
-\begin{Verbatim}[commandchars=+\[\]]
-  \mhchemoptions{+textbf[option=abc]}
+
+\section{Fine Tuning}\label{sec:FineTuning}
+
+All options explained here, can either be set using the \macro{mhchemoptions} command
+
+\begin{Verbatim}
+  \mhchemoptions{arrows=pgf}
 \end{Verbatim}
 
-\noindent
-All options can also be used in the \macro{usepackage} command in your preamble, like
+or as options to the package
 
 \begin{Verbatim}[commandchars=+()]
-  \usepackage[version=3,+textbf(option=abc)]{mhchem}
+  \usepackage[version=4,arrows=pgf]{mhchem}
 \end{Verbatim}
 
 
 \subsection{Fonts} \label{sec:Fonts}
 
-As mentioned previously, mhchem uses the current text font (if you use \macro{ce} in text mode) or the  current math font (if you use \macro{ce} in math mode). If you want, however, you can set a font that will be used for all your formulae and equations.
+mhchem uses the current text font (if you use \macro{ce} in text mode) or the  current math font (if you use \macro{ce} in math mode). If you want, however, you can set a font that will be used for all your formulae and equations.
 
-\medskip
-
-\noindent
 Inside your document, you can use
 
 \begin{Verbatim}[commandchars=+\[\]]
@@ -766,8 +697,11 @@ Inside your document, you can use
   \mhchemoptions{+textbf[mathfontcommand=\mathsf]}
 \end{Verbatim}
 
-\noindent
-in order to get sanf-serif fonts in both, text mode and math mode. There are two further options, that basically do the same, but only take the name of a single font command without the initial backslash.
+in order to get sanf-serif fonts in both, text mode and math mode.
+
+You can use any font command there, not only the mentioned ones. Please be aware that the text-font command is a font switching command (taking no arguments) while the math-font command takes one argument and typesets it.
+
+You can specify the commands by name only, i.\,e. without the \verb|\|.
 
 \begin{Verbatim}[commandchars=+\[\]]
   \mhchemoptions{+textbf[textfontname=sffamily]}
@@ -775,25 +709,18 @@ in order to get sanf-serif fonts in both, text mode and math mode. There are two
 \end{Verbatim}
 
 \noindent
-Only the latter options can be used with the \macro{usepackage} command, because the font commands are not properly defined in the preamble, yet.
-
-\medskip
-
-\noindent
-Furthermore, there are two shortcuts:
+Only the latter options can be used with the \macro{usepackage} command, because the font commands are not properly defined in the preamble, yet. The shortcut
 
 \begin{Verbatim}[commandchars=+\[\]]
   \mhchemoptions{+textbf[font=sf]}
 \end{Verbatim}
 
-\noindent
 sets the two fonts to sans-serif, as mentioned above, and
 
 \begin{Verbatim}[commandchars=+\[\]]
   \mhchemoptions{+textbf[font=]}
 \end{Verbatim}
 
-\noindent
 switches back to the default, which is equivalent to
 
 \begin{Verbatim}[commandchars=+\[\]]
@@ -803,61 +730,48 @@ switches back to the default, which is equivalent to
 
 \subsection{Arrows}
 
-By default, mhchem uses arrows that are composed of different font characters, because it uses some features of the \verb|amsmath| package. This may lead to undesirable effects when dislayed on a screen. Helmut Hänsel kindly provided a patch that used the pgf graphics package instead. pgf arrows are activated by
+By default, mhchem uses arrows that are composed of different math-font characters, because it uses some features of the amsmath package. This may lead to undesirable effects when displayed on a screen. Helmut Hänsel kindly provided a patch that used the pgf graphics package instead. pgf arrows are activated by
 
-\begin{Verbatim}[commandchars=+\[\]]
+\begin{Verbatim}[commandchars=+()]
   \usepackage[version=3,+textbf(arrows=pgf)]{mhchem}
 \end{Verbatim}
 
-\noindent
-If you use this switch inside your document with \macro{mhchemoptions}, don't forget to load the \verb|tikz| package manually. (The \verb|tikz| package is a wrapper for---and included in---the pgf bundle. The default setting is
-
-\begin{Verbatim}[commandchars=+\[\]]
-  \mhchemoptions{+textbf[arrows=font]}
-\end{Verbatim}
-
-\noindent
-Here is how it looks:
+If you use this switch inside your document with \macro{mhchemoptions}, don't forget to load the \verb|tikz| package manually. (The \verb|tikz| package is a wrapper for---and included in---the pgf bundle.)
 
 \medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \mhchemoptions{arrows=font}%
-  \ce{$A$ <->T[description] $A'$}
+\begin{SideBySideExample}[xrightmargin=3cm]
+  \mhchemoptions{arrows=font}% default
+  \ce{A <-> B}
 \end{SideBySideExample}
 
 \medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \mhchemoptions{arrows=pgf}%
-  \ce{$A$ <->T[description] $A'$}
+\begin{SideBySideExample}[xrightmargin=3cm]
+  \mhchemoptions{arrows=pgf}
+  \ce{A <-> B}
 \end{SideBySideExample}
 
 
-\subsubsection{Arrow Tips}
-
-If you do not like the standard LaTeX arrows (or the ones of your current math font, respectively), here is the option for you:
-
-\begin{Verbatim}[commandchars=+\[\]]
-  \mhchemoptions{+textbf[arrows=pgf-filled]}
-\end{Verbatim}
-
-\noindent
-The same considerations as for the \verb|pgf| option apply.
-
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
+\begin{SideBySideExample}[xrightmargin=3cm]
   \mhchemoptions{arrows=pgf-filled}
-  \ce{$A$ <->T[description] $A'$}
+  \ce{A <-> B}
 \end{SideBySideExample}
 
 
-\subsection{Stacked Superscripts}
+\subsection{Stacked Superscripts and Subscripts}
+
+\begin{SideBySideExample}[xrightmargin=3cm]
+  \mhchemoptions{layout=staggered-flat}% default
+  \ce{CrO4^2-}
+\end{SideBySideExample}
 
-If you do not like the IUPAC recommendation, you could switch to stacked superscripts
+\begin{SideBySideExample}[xrightmargin=3cm]
+  \mhchemoptions{layout=staggered-deep}
+  \ce{CrO4^2-}
+\end{SideBySideExample}
 
-\medskip
-\begin{SideBySideExample}[xrightmargin=5cm]
-  \ce{CrO4^2-}\\
-  \mhchemoptions{superscripts=stacked} \ce{CrO4^2-}
+\begin{SideBySideExample}[xrightmargin=3cm]
+  \mhchemoptions{layout=stacked}
+  \ce{CrO4^2-}% not according to IUPAC
 \end{SideBySideExample}
 
 
@@ -866,18 +780,30 @@ If you do not like the IUPAC recommendation, you could switch to stacked supersc
 \section{Major Changes}
 \label{sec:WhatSNew}
 
-\subsection{Migration from version 1}
+\subsection{Migrating from version 1}
 
-Inner \verb|-| characters are considered to be bonds.\\
-Use \verb|$| for math mode inside \macro{ce} (no braces any more).
+Inner \verb|-| characters are considered to be bonds. Use \verb|$...$| for math mode inside \macro{ce} (no braces any more).
 
 \subsection{Migrating from version 2}
 
 Meaning and usage of \macro{bond} changed.
 
+\subsection{Migrating from version 3}
+
+\verb|{...}| does escape to text now, not math. \verb|$...$| does only `half-escape' to math---check the results. Additional spaces will be inserted: A \verb|$x\,$H2O| should be changed to \verb|$x$ H2O|. Appearance of bonds, radical dot, $x$, single-letter variables, \verb|-| in subscripts etc. slightly changed---check if this fits with your font, in particular your text font. Check all complex subscripts and superscripts (more than just number or a charge). The arrow arguments are set with the same syntax as the \macro{ce} command---use \verb|$...$| or \verb|${...}$| for math. Deprecated commands like \macro{cf}, \verb|,| and \verb|`| and \macro{hyphen} and \macro{cmath} were removed completely. \macro{cee} was removed---just use \macro{ce}.
+
 
 \section{Most Recent Changes}% check
 
+\minisec{2015-04-07 mhchem v4.00}
+\begin{compactitem}
+\item many syntax improvements
+\item many layout improvements
+\item stricter distinction between text font and math font, many math features are translated into their text equivalent, e.g. italic variables
+\item new options
+\item some removed commands
+\end{compactitem}
+
 \minisec{2015-03-13 mhchem v3.21}
 \begin{compactitem}
 \item rewrote further large parts using \LaTeX3
@@ -899,58 +825,13 @@ Meaning and usage of \macro{bond} changed.
 \item several fixes for text above and below arrows
 \end{compactitem}
 
-\minisec{2014-03-27 mhchem v3.17}
-\begin{compactitem}
-\item fix of the 3.16 expansion fix -- sorry, my quality control failed
-\end{compactitem}
-
-\minisec{2014-03-20 mhchem v3.16}
-\begin{compactitem}
-\item fix: \verb|\bond| not expanded too early -- thanks to Heiko Oberdiek
-\item fix: \verb|\cee| understands \verb|\\[10pt]| -- thanks to David Carlisle
-\end{compactitem}
-
-\minisec{2014-02-01 mhchem v3.15}
-\begin{compactitem}
-\item follow the IUPAC Red Book more closely (staggered superscripts, \ce{NO3-})
-\item rewrote large parts using \LaTeX3, needs package expl3
-\item added: \verb|\bond{1}|, \verb|\bond{2}|, \verb|\bond{3}| (because \verb|#| cannot be used in all contexts)
-\end{compactitem}
-
-\minisec{2013-06-23 mhchem v3.13}
-\begin{compactitem}
-\item compatibility with many more babel languages
-\item fraction possible in amounts (\verb|\ce{0.5H2O}|)
-\end{compactitem}
-
-\minisec{2013-06-17 mhchem v3.12}
-\begin{compactitem}
-\item fixed: incompatibility with babel Czech
-\item major internal refactorings
-\end{compactitem}
-
-\minisec{2011-06-03 mhchem v3.11}
-\begin{compactitem}
-\item fixed: incompatibility with mathdesign and other font-related packages
-\end{compactitem}
-
-\minisec{2011-04-29 mhchem v3.10}
-\begin{compactitem}
-\item fixed: incompatibility with biblatex
-\end{compactitem}
-
-\minisec{2011-03-18 mhchem v3.09}
-\begin{compactitem}
-  \item fixed: \verb|_{$x$}| now works properly
-\end{compactitem}
-
 
 
 \chapter{The hpstatement Package and the rsphrase Package}\label{sec:rsphrase}
 
 The \textbf{hpstatement} package contains all official
 hazard statements and precautionary statements (H and P) of the
-Globally Harmonized System of Classification and Labeling of Chemicals (GHS)
+Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
 and of the CLP Regulation of the European Union.
 
 The statements are available in
@@ -972,13 +853,13 @@ Latvian,
 Lithuanian,
 Maltese,
 Polish,
-Portugese,
+Portuguese,
 Romanian,
 Slovak,
 Slovenian,
 Spanish or
 Swedish,
-and would like to help offering the statments in those languages, please contact me.
+and would like to help offering the statements in those languages, please contact me.
 
 \bigskip
 
@@ -996,7 +877,7 @@ Please be advised that, as stated in the license, the authors provide no warrant
 \section{Usage}
 
 The \textbf{hpstatement} package provides two commands: \verb|\hpstatement| and
-\verb|\hpnumber|. \verb|\hpstatement| insterts the statement's text,
+\verb|\hpnumber|. \verb|\hpstatement| inserts the statement's text,
 \verb|\hpnumber| it's formatted number.\bigskip
 
 \begin{addmargin}[1em]{0em}
diff --git a/Master/texmf-dist/tex/latex/mhchem/mhchem.sty b/Master/texmf-dist/tex/latex/mhchem/mhchem.sty
index 571c78dda85..f2940915438 100644
--- a/Master/texmf-dist/tex/latex/mhchem/mhchem.sty
+++ b/Master/texmf-dist/tex/latex/mhchem/mhchem.sty
@@ -27,77 +27,26 @@
 % This work consists of all files listed in manifest.txt.
 %
 %
-\ProvidesPackage{mhchem}[2015/03/13 v3.21 for typesetting chemical formulae]
+\ProvidesPackage{mhchem}[2015/04/07 v4.00 for typesetting chemical formulae]
 \RequirePackage{expl3}
 \RequirePackage{l3keys2e}
 \RequirePackage{l3regex}
 \RequirePackage{calc}[1998/07/07]
 \RequirePackage{amsmath}
 \RequirePackage{graphics}
-\RequirePackage{ifthen}  %
+\RequirePackage{ifthen}
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%   misc   %%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 \DeclareMathSymbol{\mhchem@hyphen}{0}{operators}{45}
-\def\mhchem@END{\mhchem@END}
 \def\mhchem@macro{}
 
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%   \cee   %%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-
-\ExplSyntaxOn
-
-\newcommand*{\cee}[1]
-  {
-    \cesplit
-      {
-        { \c{\\}(\[.*?\])? } { \0 }
-        { \& } { \0 }
-      }
-      {#1}
-  }
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%   \cesplit   %%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-
-\cs_generate_variant:Nn \regex_replace_all:nnN { VnN }
-\bool_new:N \__mhchem_cesplit_odd_bool
-
-\newcommand\cesplit[2]
-  {
-    \bool_set_true:N \__mhchem_cesplit_odd_bool
-
-    \tl_set:Nn \l_tmpa_tl { \__mhchem_ce:n {#2} }
-
-    \tl_map_inline:nn {#1}
-      {
-        \bool_if:NTF \__mhchem_cesplit_odd_bool
-          {
-            \tl_set:Nn \__mhchem_cesplit_key_tl {##1}
-            \bool_set_false:N \__mhchem_cesplit_odd_bool
-          }
-        % else
-          {
-            \regex_replace_all:VnN
-              \__mhchem_cesplit_key_tl
-              { \cE] ##1 \c{__mhchem_ce:n}\cB[ }
-              \l_tmpa_tl
-            \bool_set_true:N \__mhchem_cesplit_odd_bool
-          }
-      }
-    \tl_use:N \l_tmpa_tl
-  }
-
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%   global helpers   %%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-\ExplSyntaxOff
-
 \def\mhchem@appendToks#1#2{%
   #1=\expandafter{\the#1#2}%
 }
@@ -105,9 +54,19 @@
 \ExplSyntaxOn
 
 \cs_generate_variant:Nn \str_if_eq:nnTF { Vn }
-\cs_generate_variant:Nn \peek_catcode_remove:NTF { oTF }
-\cs_generate_variant:Nn \peek_catcode:NTF { oTF }
 \cs_generate_variant:Nn \str_case:nnn { Vnn }
+\cs_generate_variant:Nn \regex_match:nnTF { nV }
+\cs_generate_variant:Nn \regex_match:nnTF { no }
+\cs_new_protected:Npn \__mhchem_regex_peek:nTF #1 #2 #3
+  {
+    \peek_catcode:NTF ##
+      {#3}
+      {
+        \regex_match:noTF
+        { \A the\ (character|letter)\ (#1) \Z }
+        { \token_to_meaning:N \l_peek_token } {#2} {#3}
+      }
+  }
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%   loop helpers   %%%%%%%%%%
@@ -123,26 +82,49 @@
     \tl_put_right:Nn #1 { { #3 } }
     #2
   }
+\cs_new_protected:Npn \__mhchem_loopHelper_appendNextGroup_prefix_ifEmpty:NnnNn #1#2#3#4#5
+  {
+    \str_if_eq:nnTF {#5} {}
+      { #3 }
+      { \tl_put_right:Nn #1 { #2 { #5 } } }
+    #4
+  }
 \cs_new_protected:Npn \__mhchem_loopHelper_appendMathA:NNw #1#2#3$
   {
     \tl_put_right:Nn #1 { $ #3 $ }
     #2
   }
-\cs_new_protected:Npn \__mhchem_loopHelper_appendMathB:NNw #1#2#3$
+\cs_new_protected:Npn \__mhchem_loopHelper_appendMathAAsGroup:NNw #1#2#3$
   {
-    \tl_put_right:Nn #1 { \text { \ensuremath { #3 } } }
+    \tl_put_right:Nn #1 { $ { #3 } $ }
     #2
   }
-\cs_new_protected:Npn \__mhchem_loopHelper_appendMathAsGroup:NNw #1#2#3$
+\cs_new_protected:Npn \__mhchem_loopHelper_appendMathB:nn #1#2
+  {
+    \peek_catcode:NTF \c_group_begin_token
+      {
+        \__mhchem_loopHelper_appendMathB_aux_group:ccw
+          {#1}
+          {#2}
+      }
+      {
+        \__mhchem_loopHelper_appendMathB_aux:ccw
+          {#1}
+          {#2}
+      }
+  }
+\cs_new_protected:Npn \__mhchem_loopHelper_appendMathB_aux:NNw #1#2#3$
   {
-    \tl_put_right:Nn #1 { \text { \ensuremath { #3 } } }
+    \tl_put_right:Nn #1 { \__mhchem_cg_withinMathTokens:n { #3 } }
     #2
   }
-\cs_new_protected:Npn \__mhchem_loopHelper_appendNextTokenAsMathrm:NNn #1#2#3
+\cs_generate_variant:Nn \__mhchem_loopHelper_appendMathB_aux:NNw {ccw}
+\cs_new_protected:Npn \__mhchem_loopHelper_appendMathB_aux_group:NNw #1#2#3$
   {
-    \tl_put_right:Nn #1 { \ensuremath { \mathrm { #3 } } }
+    \tl_put_right:Nn #1 { \__mhchem_cg_withinMathTokens:n { { #3 } } }
     #2
   }
+\cs_generate_variant:Nn \__mhchem_loopHelper_appendMathB_aux_group:NNw {ccw}
 \cs_new_protected:Npn \__mhchem_loopHelper_ignoreNextToken:Nn #1#2
   {
     #1
@@ -173,7 +155,7 @@
   \fi
 }
 \expandafter\newcommand\csname ce \endcsname[1]{%
-  \mhchem@ce{#1}%
+  \mhchem@cee{#1}%
 }
 % unexpanded protect
 \def\protect@unexpand@cmd@arg#1\else#2\fi\fi\fi#3{%
@@ -198,93 +180,248 @@
 %%%%%%%%%%
 %%% /\ %%%
 
+%%%%%%%%%%%%%%%%%%%%%%%%%5%%%%%%%%
+%%%%%%%%%%   \cesplit   %%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%5%%%%%%%
 \ExplSyntaxOn
-\msg_new:nnn { mhchem } { ce/unexpected-state }
+
+\cs_generate_variant:Nn \regex_replace_all:nnN { VnN }
+\bool_new:N \l__mhchem_cesplit_odd_bool
+
+\newcommand\cesplit[2]
   {
-    Assertion~failed:~Unexpected~internal~state~'#1' (ce).~You~found~a~bug.~
-    Please~contact~the~package~author.
+    \bool_set_true:N \l__mhchem_cesplit_odd_bool
+    \tl_set:Nn \l_tmpa_tl { \__mhchem_ce:n {#2} }
+
+    \tl_map_inline:nn {#1}
+      {
+        \bool_if:NTF \l__mhchem_cesplit_odd_bool
+          {
+            \tl_set:Nn \__mhchem_cesplit_key_tl {##1}
+            \bool_set_false:N \l__mhchem_cesplit_odd_bool
+          }
+        % else
+          {
+            \regex_replace_all:VnN
+              \__mhchem_cesplit_key_tl
+              { \cE] ##1 \c{__mhchem_ce:n}\cB[ }
+              \l_tmpa_tl
+            \bool_set_true:N \l__mhchem_cesplit_odd_bool
+          }
+      }
+    \tl_use:N \l_tmpa_tl
   }
-\bool_new:N \__mhchem_ce_ceActive_bool
-\bool_set_false:N \__mhchem_ce_ceActive_bool
-\tl_new:N \__mhchem_ce_state_tl
 
-\tl_new:N \__mhchem_ce_arrowName_tl
-\tl_new:N \__mhchem_ce_arrowTypeOne_tl
-\tl_new:N \__mhchem_ce_arrowTextOne_tl
-\tl_new:N \__mhchem_ce_arrowTypeTwo_tl
-\tl_new:N \__mhchem_ce_arrowTextTwo_tl
-\bool_new:N \__mhchem_ce_potentialSpacing_bool
-\bool_new:N \__mhchem_ce_potentialSpacing_future_bool
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%   \cee   %%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-\newcommand*\mhchem@ce[1]{
-  \__mhchem_ce:n {#1}
+\newcommand*\mhchem@cee[1]{
+  \__mhchem_cee:n {#1}
 }
+
+\ExplSyntaxOn
+\cs_new_protected:Npn \__mhchem_cee:n #1
+  {
+    \cesplit
+      {
+        { \c{\\}(\[.*?\])? } { \0 }
+        { \& } { \0 }
+      }
+      {#1}
+  }
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%   \__mhchem_ce:n   %%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+\msg_new:nnn { mhchem } { ce / unexpected-state }
+  {
+    Assertion~failed:~Unexpected~internal~state~'#1' (ce).~You~found~a~bug.~
+    Please~contact~the~package~author.
+  }
+\bool_new:N \l__mhchem_ce_ceActive_bool
+\bool_set_false:N \l__mhchem_ce_ceActive_bool
+\tl_new:N \l__mhchem_ce_state_tl
+
+\int_new:N \l__mhchem_ce_distanceFromLastComma_int
+\tl_new:N \l__mhchem_ce_result_tl
+\tl_new:N \l__mhchem_ce_part_tl
+\tl_new:N \l__mhchem_ce_arrowName_tl
+\tl_new:N \l__mhchem_ce_arrowTypeOne_tl
+\tl_new:N \l__mhchem_ce_arrowTextOne_tl
+\tl_new:N \l__mhchem_ce_arrowTypeTwo_tl
+\tl_new:N \l__mhchem_ce_arrowTextTwo_tl
+\bool_new:N \l__mhchem_ce_potentialSpacing_bool
+\bool_new:N \l__mhchem_ce_potentialSpacing_future_bool
+
 \cs_new_protected:Npn \__mhchem_ce:n #1
   {
     \group_begin:
-    \bool_if:NF \__mhchem_cf_cfActive_bool
+    \mhchem@hook@beforeCe
+    \bool_if:NF \l__mhchem_ce_ceActive_bool
       {
-        \bool_set_true:N \__mhchem_cf_cfActive_bool
-        \__mhchem_defMathOrText:
+        \bool_set_true:N \l__mhchem_ce_ceActive_bool
+        \__mhchem_output_defMathOrText:
+        \def\hyphen{\mhchem@hyphen}%
+        \let\mhchem@orig@alpha\alpha
+        \let\mhchem@orig@beta\beta
+        \let\mhchem@orig@gamma\gamma
+        \let\mhchem@orig@delta\delta
+        \let\mhchem@orig@epsilon\epsilon
+        \let\mhchem@orig@zeta\zeta
+        \let\mhchem@orig@eta\eta
+        \let\mhchem@orig@theta\theta
+        \let\mhchem@orig@iota\iota
+        \let\mhchem@orig@kappa\kappa
+        \let\mhchem@orig@lambda\lambda
+        \let\mhchem@orig@mu\mu
+        \let\mhchem@orig@nu\nu
+        \let\mhchem@orig@xi\xi
+        \let\mhchem@orig@omicron\omicron
+        \let\mhchem@orig@pi\pi
+        \let\mhchem@orig@rho\rho
+        \let\mhchem@orig@sigma\sigma
+        \let\mhchem@orig@tau\tau
+        \let\mhchem@orig@upsilon\upsilon
+        \let\mhchem@orig@phi\phi
+        \let\mhchem@orig@chi\chi
+        \let\mhchem@orig@psi\psi
+        \let\mhchem@orig@omega\omega
+        \let\mhchem@orig@Alpha\Alpha
+        \let\mhchem@orig@Beta\Beta
+        \let\mhchem@orig@Gamma\Gamma
+        \let\mhchem@orig@Delta\Delta
+        \let\mhchem@orig@Epsilon\Epsilon
+        \let\mhchem@orig@Zeta\Zeta
+        \let\mhchem@orig@Eta\Eta
+        \let\mhchem@orig@Theta\Theta
+        \let\mhchem@orig@Iota\Iota
+        \let\mhchem@orig@Kappa\Kappa
+        \let\mhchem@orig@Lambda\Lambda
+        \let\mhchem@orig@Mu\Mu
+        \let\mhchem@orig@Nu\Nu
+        \let\mhchem@orig@Xi\Xi
+        \let\mhchem@orig@Omicron\Omicron
+        \let\mhchem@orig@Pi\Pi
+        \let\mhchem@orig@Rho\Rho
+        \let\mhchem@orig@Sigma\Sigma
+        \let\mhchem@orig@Tau\Tau
+        \let\mhchem@orig@Upsilon\Upsilon
+        \let\mhchem@orig@Phi\Phi
+        \let\mhchem@orig@Chi\Chi
+        \let\mhchem@orig@Psi\Psi
+        \let\mhchem@orig@Omega\Omega
+        \def\alpha{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@alpha}}
+        \def\beta{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@beta}}
+        \def\gamma{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@gamma}}
+        \def\delta{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@delta}}
+        \def\epsilon{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@epsilon}}
+        \def\zeta{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@zeta}}
+        \def\eta{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@eta}}
+        \def\theta{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@theta}}
+        \def\iota{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@iota}}
+        \def\kappa{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@kappa}}
+        \def\lambda{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@lambda}}
+        \def\mu{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@mu}}
+        \def\nu{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@nu}}
+        \def\xi{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@xi}}
+        \def\omicron{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@omicron}}
+        \def\pi{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@pi}}
+        \def\rho{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@rho}}
+        \def\sigma{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@sigma}}
+        \def\tau{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@tau}}
+        \def\upsilon{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@upsilon}}
+        \def\phi{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@phi}}
+        \def\chi{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@chi}}
+        \def\psi{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@psi}}
+        \def\omega{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@omega}}
+        \def\Alpha{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Alpha}}
+        \def\Beta{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Beta}}
+        \def\Gamma{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Gamma}}
+        \def\Delta{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Delta}}
+        \def\Epsilon{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Epsilon}}
+        \def\Zeta{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Zeta}}
+        \def\Eta{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Eta}}
+        \def\Theta{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Theta}}
+        \def\Iota{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Iota}}
+        \def\Kappa{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Kappa}}
+        \def\Lambda{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Lambda}}
+        \def\Mu{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Mu}}
+        \def\Nu{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Nu}}
+        \def\Xi{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Xi}}
+        \def\Omicron{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Omicron}}
+        \def\Pi{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Pi}}
+        \def\Rho{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Rho}}
+        \def\Sigma{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Sigma}}
+        \def\Tau{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Tau}}
+        \def\Upsilon{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Upsilon}}
+        \def\Phi{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Phi}}
+        \def\Chi{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Chi}}
+        \def\Psi{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Psi}}
+        \def\Omega{\__mhchem_output_escapeToItalicMath:n{\mhchem@orig@Omega}}
       }
-    \def\hyphen{\mhchem@hyphen}%
-    \tl_clear_new:N \__mhchem_ce_result_tl
-    \tl_clear_new:N \__mhchem_ce_part_tl
-    \bool_set_false:N \__mhchem_ce_potentialSpacing_bool
-    \tl_set:Nn \__mhchem_ce_state_tl { c }
+    \tl_clear:N \l__mhchem_ce_result_tl
+    \tl_clear:N \l__mhchem_ce_part_tl
+    \tl_set:Nn \l__mhchem_ce_state_tl { c }
+    \bool_set_false:N \l__mhchem_ce_potentialSpacing_bool
+    \int_set:Nn \l__mhchem_ce_distanceFromLastComma_int { 9 }
+    \tl_clear:N \l__mhchem_cf_lastElement_tl
     \__mhchem_ce_loop: #1 \q_recursion_stop
-    \int_compare:nTF { \__mhchem_option_version_int > 1 }
-      { \tl_use:N \__mhchem_ce_result_tl }
-      { \ensuremath{\tl_use:N \__mhchem_ce_result_tl}  }
+    \int_compare:nTF { \l__mhchem_option_version_int > 1 }
+      { \tl_use:N \l__mhchem_ce_result_tl }
+      { \ensuremath{\tl_use:N \l__mhchem_ce_result_tl} }
+    \mhchem@hook@afterCe
     \group_end:
   }
 \cs_new_protected:Npn \__mhchem_ce_loop:
   {
-    \str_case:Vnn \__mhchem_ce_state_tl
+    \int_incr:N \l__mhchem_ce_distanceFromLastComma_int
+    \str_case:Vnn \l__mhchem_ce_state_tl
       {
         { c }
           {
-            \str_case:Vnn \__mhchem_ce_part_tl
+            \str_case:Vnn \l__mhchem_ce_part_tl
               {
                 { + }
                   {
-                    \tl_put_right:Nn \__mhchem_ce_result_tl { \ensuremath{{}+{}} }
-                    \tl_clear:N \__mhchem_ce_part_tl
-                    \tl_set:Nn \__mhchem_ce_state_tl { a-end }
+                  \tl_put_right:Nn \l__mhchem_ce_result_tl { \__mhchem_output_operatorPlus: }
+                    \tl_clear:N \l__mhchem_ce_part_tl
+                    \tl_set:Nn \l__mhchem_ce_state_tl { a-end }
                   }
                 { -> }
                   {
-                    \tl_set:Nn \__mhchem_ce_arrowName_tl { yields }
+                    \tl_set:Nn \l__mhchem_ce_arrowName_tl { yields }
                     \__mhchem_ce_loop_startArrow:
                   }
                 { <- }
                   {
-                    \tl_set:Nn \__mhchem_ce_arrowName_tl { yieldsLeft }
+                    \tl_set:Nn \l__mhchem_ce_arrowName_tl { yieldsLeft }
                     \__mhchem_ce_loop_startArrow:
                   }
                 { <--> }
                   {
-                    \tl_set:Nn \__mhchem_ce_arrowName_tl { yieldsLeftRight }
+                    \tl_set:Nn \l__mhchem_ce_arrowName_tl { yieldsLeftRight }
                     \__mhchem_ce_loop_startArrow:
                   }
                 { <-> }
                   {
-                    \tl_set:Nn \__mhchem_ce_arrowName_tl { mesomerism }
+                    \tl_set:Nn \l__mhchem_ce_arrowName_tl { mesomerism }
                     \__mhchem_ce_loop_startArrow:
                   }
                 { <=> }
                   {
-                    \tl_set:Nn \__mhchem_ce_arrowName_tl { equilibrium }
+                    \tl_set:Nn \l__mhchem_ce_arrowName_tl { equilibrium }
                     \__mhchem_ce_loop_startArrow:
                   }
                 { <<=> }
                   {
-                    \tl_set:Nn \__mhchem_ce_arrowName_tl { equilibriumLeft }
+                    \tl_set:Nn \l__mhchem_ce_arrowName_tl { equilibriumLeft }
                     \__mhchem_ce_loop_startArrow:
                   }
                 { <=>> }
                   {
-                    \tl_set:Nn \__mhchem_ce_arrowName_tl { equilibriumRight }
+                    \tl_set:Nn \l__mhchem_ce_arrowName_tl { equilibriumRight }
                     \__mhchem_ce_loop_startArrow:
                   }
               }
@@ -296,37 +433,59 @@
       {
         \__mhchem_ce_output:
       }{
-    \str_case:Vnn \__mhchem_ce_state_tl
+    \str_case:Vnn \l__mhchem_ce_state_tl
       {
         { c }
           {
             \peek_charcode_remove:NTF \c_space_token
               {
-                \__mhchem_ce_output:
-                \bool_if:NTF \__mhchem_ce_potentialSpacingAllowed_bool
-                  { \bool_set_true:N \__mhchem_ce_potentialSpacing_bool }
-                  { \bool_set_false:N \__mhchem_ce_potentialSpacing_bool }
+                \int_compare:nTF { \l__mhchem_ce_distanceFromLastComma_int = 1 }
+                  {
+                    \__mhchem_ce_output:
+                    \bool_set_false:N \l__mhchem_ce_potentialSpacing_bool
+                  }
+                  {
+                    \__mhchem_ce_output:
+                    \bool_if:NTF \__mhchem_ce_potentialSpacingAllowed_bool
+                      { \bool_set_true:N \l__mhchem_ce_potentialSpacing_bool }
+                      { \bool_set_false:N \l__mhchem_ce_potentialSpacing_bool }
+                  }
                 \__mhchem_ce_loop:
               }{
-            \peek_catcode_remove:NTF \c_math_toggle_token
+            \peek_charcode:NTF ,
               {
-                \__mhchem_loopHelper_appendMathA:NNw
-                  \__mhchem_ce_part_tl
+                \int_set:Nn \l__mhchem_ce_distanceFromLastComma_int { 0 }
+                \__mhchem_loopHelper_appendNextToken:NNn
+                  \l__mhchem_ce_part_tl
                   \__mhchem_ce_loop:
               }{
+            \peek_catcode_remove:NTF \c_math_toggle_token
+              {
+                \peek_catcode:NTF \c_group_begin_token
+                  {
+                    \__mhchem_loopHelper_appendMathAAsGroup:NNw
+                      \l__mhchem_ce_part_tl
+                      \__mhchem_ce_loop:
+                  }
+                  {
+                    \__mhchem_loopHelper_appendMathA:NNw
+                      \l__mhchem_ce_part_tl
+                      \__mhchem_ce_loop:
+                  }
+              }{
             \peek_catcode:NTF \c_group_begin_token
               {
                 \__mhchem_loopHelper_appendNextGroup:NNn
-                  \__mhchem_ce_part_tl
+                  \l__mhchem_ce_part_tl
                   \__mhchem_ce_loop:
               }
             % else
               {
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_ce_part_tl
+                  \l__mhchem_ce_part_tl
                   \__mhchem_ce_loop:
               }
-            }}
+            }}}
           }
         { a-t1 }
           {
@@ -337,56 +496,56 @@
               }{
             \peek_charcode:NTF T
               {
-                \tl_set:Nn \__mhchem_ce_state_tl { a-[1 }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-[1 }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_ce_arrowTypeOne_tl
+                  \l__mhchem_ce_arrowTypeOne_tl
                   \__mhchem_ce_loop:
               }{
             \peek_charcode:NTF M
               {
-                \tl_set:Nn \__mhchem_ce_state_tl { a-[1 }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-[1 }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_ce_arrowTypeOne_tl
+                  \l__mhchem_ce_arrowTypeOne_tl
                   \__mhchem_ce_loop:
               }{
             \peek_charcode:NTF C
               {
-                \tl_set:Nn \__mhchem_ce_state_tl { a-[1 }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-[1 }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_ce_arrowTypeOne_tl
+                  \l__mhchem_ce_arrowTypeOne_tl
                   \__mhchem_ce_loop:
               }{
             \peek_charcode:NTF [
               {
-                \tl_set:Nn \__mhchem_ce_state_tl { a-]1 }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-]1 }
                 \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_ce_loop:
               }
             % else
               {
-                \str_case:Vnn \__mhchem_ce_arrowName_tl
+                \str_case:Vnn \l__mhchem_ce_arrowName_tl
                   {
                     { yieldsLeft }
                       {
                         \peek_charcode:NTF -
                           {
-                            \tl_set:Nn \__mhchem_ce_state_tl { c }
-                            \tl_set:Nn \__mhchem_ce_part_tl { <- }
+                            \tl_set:Nn \l__mhchem_ce_state_tl { c }
+                            \tl_set:Nn \l__mhchem_ce_part_tl { <- }
                             \__mhchem_loopHelper_appendNextToken:NNn
-                              \__mhchem_ce_part_tl
+                              \l__mhchem_ce_part_tl
                               \__mhchem_ce_loop:
                           }{
                         \peek_charcode:NTF >
                           {
-                            \tl_set:Nn \__mhchem_ce_state_tl { c }
-                            \tl_set:Nn \__mhchem_ce_part_tl { <- }
+                            \tl_set:Nn \l__mhchem_ce_state_tl { c }
+                            \tl_set:Nn \l__mhchem_ce_part_tl { <- }
                             \__mhchem_loopHelper_appendNextToken:NNn
-                              \__mhchem_ce_part_tl
+                              \l__mhchem_ce_part_tl
                               \__mhchem_ce_loop:
                           }
                         % else
                           {
                             \__mhchem_ce_output:
-                            \tl_set:Nn \__mhchem_ce_state_tl { a-end }
+                            \tl_set:Nn \l__mhchem_ce_state_tl { a-end }
                             \__mhchem_ce_loop:
                           }
                         }
@@ -395,16 +554,16 @@
                       {
                         \peek_charcode:NTF >
                           {
-                            \tl_set:Nn \__mhchem_ce_state_tl { c }
-                            \tl_set:Nn \__mhchem_ce_part_tl { <=> }
+                            \tl_set:Nn \l__mhchem_ce_state_tl { c }
+                            \tl_set:Nn \l__mhchem_ce_part_tl { <=> }
                             \__mhchem_loopHelper_appendNextToken:NNn
-                              \__mhchem_ce_part_tl
+                              \l__mhchem_ce_part_tl
                               \__mhchem_ce_loop:
                           }
                         % else
                           {
                             \__mhchem_ce_output:
-                            \tl_set:Nn \__mhchem_ce_state_tl { a-end }
+                            \tl_set:Nn \l__mhchem_ce_state_tl { a-end }
                             \__mhchem_ce_loop:
                           }
                       }
@@ -412,7 +571,7 @@
                   % else
                   {
                     \__mhchem_ce_output:
-                    \tl_set:Nn \__mhchem_ce_state_tl { a-end }
+                    \tl_set:Nn \l__mhchem_ce_state_tl { a-end }
                     \__mhchem_ce_loop:
                   }
               }
@@ -422,13 +581,13 @@
           {
             \peek_charcode:NTF [
               {
-                \tl_set:Nn \__mhchem_ce_state_tl { a-]1 }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-]1 }
                 \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_ce_loop:
               }
             % else
               {
                 \__mhchem_ce_output:
-                \tl_set:Nn \__mhchem_ce_state_tl { a-end }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-end }
                 \__mhchem_ce_loop:
               }
           }
@@ -436,30 +595,30 @@
           {
             \peek_charcode_remove:NTF \c_space_token
               {
-                \tl_put_right:Nn \__mhchem_ce_arrowTextOne_tl { ~ }
+                \tl_put_right:Nn \l__mhchem_ce_arrowTextOne_tl { ~ }
                 \__mhchem_ce_loop:
               }{
             \peek_charcode:NTF ]
               {
-                \tl_set:Nn \__mhchem_ce_state_tl { a-t2 }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-t2 }
                 \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_ce_loop:
               }{
             \peek_catcode:NTF \c_group_begin_token
               {
                 \__mhchem_loopHelper_appendNextGroup:NNn
-                  \__mhchem_ce_arrowTextOne_tl
+                  \l__mhchem_ce_arrowTextOne_tl
                   \__mhchem_ce_loop:
               }{
             \peek_catcode_remove:NTF \c_math_toggle_token
               {
-                \__mhchem_loopHelper_appendMathB:NNw
-                  \__mhchem_ce_arrowTextOne_tl
-                  \__mhchem_ce_loop:
+                \__mhchem_loopHelper_appendMathB:nn
+                  { l__mhchem_ce_arrowTextOne_tl }
+                  { __mhchem_ce_loop: }
               }
             % else
               {
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_ce_arrowTextOne_tl
+                  \l__mhchem_ce_arrowTextOne_tl
                   \__mhchem_ce_loop:
               }
             }}}
@@ -473,34 +632,34 @@
               }{
             \peek_charcode:NTF T
               {
-                \tl_set:Nn \__mhchem_ce_state_tl { a-[2 }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-[2 }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_ce_arrowTypeTwo_tl
+                  \l__mhchem_ce_arrowTypeTwo_tl
                   \__mhchem_ce_loop:
               }{
             \peek_charcode:NTF M
               {
-                \tl_set:Nn \__mhchem_ce_state_tl { a-[2 }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-[2 }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_ce_arrowTypeTwo_tl
+                  \l__mhchem_ce_arrowTypeTwo_tl
                   \__mhchem_ce_loop:
               }{
             \peek_charcode:NTF C
               {
-                \tl_set:Nn \__mhchem_ce_state_tl { a-[2 }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-[2 }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_ce_arrowTypeTwo_tl
+                  \l__mhchem_ce_arrowTypeTwo_tl
                   \__mhchem_ce_loop:
               }{
             \peek_charcode:NTF [
               {
-                \tl_set:Nn \__mhchem_ce_state_tl { a-]2 }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-]2 }
                 \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_ce_loop:
               }
             % else
               {
                 \__mhchem_ce_output:
-                \tl_set:Nn \__mhchem_ce_state_tl { a-end }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-end }
                 \__mhchem_ce_loop:
               }
             }}}}
@@ -509,13 +668,13 @@
           {
             \peek_charcode:NTF [
               {
-                \tl_set:Nn \__mhchem_ce_state_tl { a-]2 }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-]2 }
                 \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_ce_loop:
               }
             % else
               {
                 \__mhchem_ce_output:
-                \tl_set:Nn \__mhchem_ce_state_tl { a-end }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-end }
                 \__mhchem_ce_loop:
               }
           }
@@ -523,39 +682,39 @@
           {
             \peek_charcode_remove:NTF \c_space_token
               {
-                \tl_put_right:Nn \__mhchem_ce_arrowTextTwo_tl { ~ }
+                \tl_put_right:Nn \l__mhchem_ce_arrowTextTwo_tl { ~ }
                 \__mhchem_ce_loop:
               }{
             \peek_charcode:NTF ]
               {
                 \__mhchem_ce_output:
-                \tl_set:Nn \__mhchem_ce_state_tl { a-end }
+                \tl_set:Nn \l__mhchem_ce_state_tl { a-end }
                 \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_ce_loop:
               }{
             \peek_catcode:NTF \c_group_begin_token
               {
                 \__mhchem_loopHelper_appendNextGroup:NNn
-                  \__mhchem_ce_arrowTextTwo_tl
+                  \l__mhchem_ce_arrowTextTwo_tl
                   \__mhchem_ce_loop:
               }{
             \peek_catcode_remove:NTF \c_math_toggle_token
               {
-                \__mhchem_loopHelper_appendMathB:NNw
-                  \__mhchem_ce_arrowTextTwo_tl
-                  \__mhchem_ce_loop:
+                \__mhchem_loopHelper_appendMathB:nn
+                  { l__mhchem_ce_arrowTextTwo_tl }
+                  { __mhchem_ce_loop: }
               }
             % else
               {
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_ce_arrowTextTwo_tl
+                  \l__mhchem_ce_arrowTextTwo_tl
                   \__mhchem_ce_loop:
               }
             }}}
           }
         { a-end }
           {
-            \bool_set_false:N \__mhchem_ce_potentialSpacing_bool
-            \tl_set:Nn \__mhchem_ce_state_tl { c }
+            \bool_set_false:N \l__mhchem_ce_potentialSpacing_bool
+            \tl_set:Nn \l__mhchem_ce_state_tl { c }
             \peek_charcode_remove:NTF \c_space_token
               {
                 \__mhchem_ce_loop:
@@ -567,10 +726,10 @@
           }
       }
       {
-        \msg_error:nnx { mhchem } { ce/unexpected-state }
-          { \__mhchem_ce_state_tl }
+        \msg_error:nnx { mhchem } { ce / unexpected-state }
+          { \l__mhchem_ce_state_tl }
         \__mhchem_loopHelper_appendNextToken:NNn
-          \__mhchem_ce_result_tl
+          \l__mhchem_ce_result_tl
           \__mhchem_ce_loop:
       }
     }
@@ -578,63 +737,82 @@
 \cs_new_protected:Npn \__mhchem_ce_output:
   {
     \bool_set_true:N \__mhchem_ce_potentialSpacingAllowed_bool
-    \str_case:Vnn \__mhchem_ce_state_tl
+    \str_case:Vnn \l__mhchem_ce_state_tl
       {
         { c }
           {
-            \str_if_eq:VnTF \__mhchem_ce_part_tl { - }
-              {
-                \tl_put_right:Nn \__mhchem_ce_result_tl { \ensuremath{{}-{}} }
-                \bool_set_false:N \__mhchem_ce_potentialSpacingAllowed_bool
-              }{
-            \str_if_eq:VnTF \__mhchem_ce_part_tl { (v) }
+            \str_case:Vnn \l__mhchem_ce_part_tl
               {
-                \tl_put_right:Nn \__mhchem_ce_result_tl
-                  { \ensuremath{{}\mathop{\downarrow}{}} }
-                \bool_set_false:N \__mhchem_ce_potentialSpacingAllowed_bool
-              }{
-            \str_if_eq:VnTF \__mhchem_ce_part_tl { v }
-              {
-                \tl_put_right:Nn \__mhchem_ce_result_tl
-                  { \ensuremath{{}\mathop{\downarrow}{}} }
-                \bool_set_false:N \__mhchem_ce_potentialSpacingAllowed_bool
-              }{
-            \str_if_eq:VnTF \__mhchem_ce_part_tl { (^) }
-              {
-                \tl_put_right:Nn \__mhchem_ce_result_tl
-                  { \ensuremath{{}\mathop{\uparrow}{}} }
-                \bool_set_false:N \__mhchem_ce_potentialSpacingAllowed_bool
-              }{
-            \str_if_eq:VnTF \__mhchem_ce_part_tl { ^ }
-              {
-                \tl_put_right:Nn \__mhchem_ce_result_tl
-                  { \ensuremath{{}\mathop{\uparrow}{}} }
-                \bool_set_false:N \__mhchem_ce_potentialSpacingAllowed_bool
+                { - }
+                  {
+                    \tl_put_right:Nn \l__mhchem_ce_result_tl { \ensuremath{{}-{}} }
+                    \bool_set_false:N \__mhchem_ce_potentialSpacingAllowed_bool
+                  }
+                { (v) }
+                  {
+                    \tl_put_right:Nn \l__mhchem_ce_result_tl
+                      { \ensuremath{{}\mathop{\downarrow}{}} }
+                    \bool_set_false:N \__mhchem_ce_potentialSpacingAllowed_bool
+                  }
+                { v }
+                  {
+                    \tl_put_right:Nn \l__mhchem_ce_result_tl
+                      { \ensuremath{{}\mathop{\downarrow}{}} }
+                    \bool_set_false:N \__mhchem_ce_potentialSpacingAllowed_bool
+                  }
+                { (^) }
+                  {
+                    \tl_put_right:Nn \l__mhchem_ce_result_tl
+                      { \ensuremath{{}\mathop{\uparrow}{}} }
+                    \bool_set_false:N \__mhchem_ce_potentialSpacingAllowed_bool
+                  }
+                { ^ }
+                  {
+                    \tl_put_right:Nn \l__mhchem_ce_result_tl
+                      { \ensuremath{{}\mathop{\uparrow}{}} }
+                    \bool_set_false:N \__mhchem_ce_potentialSpacingAllowed_bool
+                  }
+                { = }
+                  {
+                    \tl_put_right:Nn \l__mhchem_ce_result_tl
+                      { \__mhchem_output_operatorEquals: }
+                    \bool_set_false:N \__mhchem_ce_potentialSpacingAllowed_bool
+                  }
+                { . }
+                  {
+                    \tl_put_right:Nn \l__mhchem_ce_result_tl
+                      { \__mhchem_output_additionCompound: }
+                    \bool_set_false:N \__mhchem_ce_potentialSpacingAllowed_bool
+                  }
+                { * }
+                  {
+                    \tl_put_right:Nn \l__mhchem_ce_result_tl
+                      { \__mhchem_output_additionCompound: }
+                    \bool_set_false:N \__mhchem_ce_potentialSpacingAllowed_bool
+                  }
+                {  }
+                  {
+                  }
               }
             % else
               {
-                \tl_if_empty:NTF \__mhchem_ce_part_tl
-                {}
-                {
-                  \bool_if:NT \__mhchem_ce_potentialSpacing_bool
-                    {
-                      \int_compare:nT { \__mhchem_option_version_int > 3 }
-                        { \tl_put_right:Nn \__mhchem_ce_result_tl { \mhchem@option@skipAfterAmount } }
-                    }
-                  \tl_put_right:Nx \__mhchem_ce_result_tl
-                    {
-                      \exp_not:N \__mhchem_cf:nn
-                      {}
-                      { \exp_not:V \__mhchem_ce_part_tl }
-                    }
-                }
+                \bool_if:NT \l__mhchem_ce_potentialSpacing_bool
+                  {
+                    \int_compare:nT { \l__mhchem_option_version_int > 3 }
+                      { \tl_put_right:Nn \l__mhchem_ce_result_tl { \mhchem@option@skipAfterAmount } }
+                  }
+                \tl_put_right:Nx \l__mhchem_ce_result_tl
+                  {
+                    \exp_not:N \__mhchem_cf:nn
+                    {}
+                    { \exp_not:V \l__mhchem_ce_part_tl }
+                  }
               }
-            }}}}
           }
         { a-t1 }
           {
             \__mhchem_ce_outputArrow:ooooo
-              { \__mhchem_ce_arrowName_tl }
+              { \l__mhchem_ce_arrowName_tl }
               {}
               {}
               {}
@@ -643,92 +821,92 @@
         { a-[1 }
           {
             \__mhchem_ce_outputArrow:ooooo
-              { \__mhchem_ce_arrowName_tl }
+              { \l__mhchem_ce_arrowName_tl }
               {}
               {}
               {}
               {}
-            \tl_set:NV \__mhchem_ce_part_tl \__mhchem_ce_arrowTypeOne_tl
-            \tl_set:Nn \__mhchem_ce_state_tl { c }
-            \bool_set_false:N \__mhchem_ce_potentialSpacing_bool
+            \tl_set:NV \l__mhchem_ce_part_tl \l__mhchem_ce_arrowTypeOne_tl
+            \tl_set:Nn \l__mhchem_ce_state_tl { c }
+            \bool_set_false:N \l__mhchem_ce_potentialSpacing_bool
             \__mhchem_ce_output:
           }
         { a-]1 }
           {
             \__mhchem_ce_outputArrow:ooooo
-              { \__mhchem_ce_arrowName_tl }
-              { \__mhchem_ce_arrowTypeOne_tl }
-              { \__mhchem_ce_arrowTextOne_tl }
+              { \l__mhchem_ce_arrowName_tl }
+              { \l__mhchem_ce_arrowTypeOne_tl }
+              { \l__mhchem_ce_arrowTextOne_tl }
               {}
               {}
           }
         { a-t2 }
           {
             \__mhchem_ce_outputArrow:ooooo
-              { \__mhchem_ce_arrowName_tl }
-              { \__mhchem_ce_arrowTypeOne_tl }
-              { \__mhchem_ce_arrowTextOne_tl }
+              { \l__mhchem_ce_arrowName_tl }
+              { \l__mhchem_ce_arrowTypeOne_tl }
+              { \l__mhchem_ce_arrowTextOne_tl }
               {}
               {}
           }
         { a-[2 }
           {
             \__mhchem_ce_outputArrow:ooooo
-              { \__mhchem_ce_arrowName_tl }
-              { \__mhchem_ce_arrowTypeOne_tl }
-              { \__mhchem_ce_arrowTextOne_tl }
+              { \l__mhchem_ce_arrowName_tl }
+              { \l__mhchem_ce_arrowTypeOne_tl }
+              { \l__mhchem_ce_arrowTextOne_tl }
               {}
               {}
-            \tl_set:NV \__mhchem_ce_part_tl \__mhchem_ce_arrowTypeTwo_tl
-            \tl_set:Nn \__mhchem_ce_state_tl { c }
-            \bool_set_false:N \__mhchem_ce_potentialSpacing_bool
+            \tl_set:NV \l__mhchem_ce_part_tl \l__mhchem_ce_arrowTypeTwo_tl
+            \tl_set:Nn \l__mhchem_ce_state_tl { c }
+            \bool_set_false:N \l__mhchem_ce_potentialSpacing_bool
             \__mhchem_ce_output:
           }
         { a-]2 }
           {
             \__mhchem_ce_outputArrow:ooooo
-              { \__mhchem_ce_arrowName_tl }
-              { \__mhchem_ce_arrowTypeOne_tl }
-              { \__mhchem_ce_arrowTextOne_tl }
-              { \__mhchem_ce_arrowTypeTwo_tl }
-              { \__mhchem_ce_arrowTextTwo_tl }
+              { \l__mhchem_ce_arrowName_tl }
+              { \l__mhchem_ce_arrowTypeOne_tl }
+              { \l__mhchem_ce_arrowTextOne_tl }
+              { \l__mhchem_ce_arrowTypeTwo_tl }
+              { \l__mhchem_ce_arrowTextTwo_tl }
           }
       }
       {}
-    \tl_clear:N \__mhchem_ce_part_tl
-    \tl_set:Nn \__mhchem_ce_state_tl { c }
-    \bool_set_false:N \__mhchem_ce_potentialSpacing_bool
+    \tl_clear:N \l__mhchem_ce_part_tl
+    \tl_set:Nn \l__mhchem_ce_state_tl { c }
+    \bool_set_false:N \l__mhchem_ce_potentialSpacing_bool
   }
 \cs_new_protected:Npn \__mhchem_ce_outputArrow:nnnnn #1#2#3#4#5
   {
-    \tl_put_right:Nn \__mhchem_ce_result_tl
+    \tl_put_right:Nn \l__mhchem_ce_result_tl
       {
         \__mhchem_arrow_deploy:nnnnn {#1} {#2} {#3} {#4} {#5}
       }
-    \tl_clear:N \__mhchem_ce_part_tl
-    \tl_set:Nn \__mhchem_ce_state_tl { c }
+    \tl_clear:N \l__mhchem_ce_part_tl
+    \tl_set:Nn \l__mhchem_ce_state_tl { c }
   }
 \cs_generate_variant:Nn \__mhchem_ce_outputArrow:nnnnn {ooooo}
 \cs_new_protected:Npn \__mhchem_ce_loop_startArrow:
   {
-    \tl_set:Nn \__mhchem_ce_state_tl { a-t1 }
-    \tl_clear:N \__mhchem_ce_arrowTypeOne_tl
-    \tl_clear:N \__mhchem_ce_arrowTextOne_tl
-    \tl_clear:N \__mhchem_ce_arrowTypeTwo_tl
-    \tl_clear:N \__mhchem_ce_arrowTextTwo_tl
-    \tl_clear:N \__mhchem_ce_part_tl
+    \tl_set:Nn \l__mhchem_ce_state_tl { a-t1 }
+    \tl_clear:N \l__mhchem_ce_arrowTypeOne_tl
+    \tl_clear:N \l__mhchem_ce_arrowTextOne_tl
+    \tl_clear:N \l__mhchem_ce_arrowTypeTwo_tl
+    \tl_clear:N \l__mhchem_ce_arrowTextTwo_tl
+    \tl_clear:N \l__mhchem_ce_part_tl
   }
 \cs_new_protected:Npn \__mhchem_ce_loop_abortArrow:
   {
-    \tl_put_right:Nx \__mhchem_ce_part_tl
+    \tl_put_right:Nx \l__mhchem_ce_part_tl
       {
-        \tl_set:Nn \__mhchem_ce_state_tl { a-t1 }
-        \exp_not:V \__mhchem_ce_arrowTypeOne_tl
-        \exp_not:V \__mhchem_ce_arrowTextOne_tl
-        \exp_not:V \__mhchem_ce_arrowTypeTwo_tl
-        \exp_not:V \__mhchem_ce_arrowTextTwo_tl
+        \tl_set:Nn \l__mhchem_ce_state_tl { a-t1 }
+        \exp_not:V \l__mhchem_ce_arrowTypeOne_tl
+        \exp_not:V \l__mhchem_ce_arrowTextOne_tl
+        \exp_not:V \l__mhchem_ce_arrowTypeTwo_tl
+        \exp_not:V \l__mhchem_ce_arrowTextTwo_tl
       }
-    \tl_set:Nn \__mhchem_ce_state_tl { c }
+    \tl_set:Nn \l__mhchem_ce_state_tl { c }
   }
 \ExplSyntaxOff
 
@@ -751,8 +929,8 @@
       {
         {  }
           {
-            \int_compare:nTF { \__mhchem_option_version_int > 3 }
-              { \cs:w mhchem@arrow@#1T \cs_end: {#3}{#5} }
+            \int_compare:nTF { \l__mhchem_option_version_int > 3 }
+              { \cs:w mhchem@arrow@#1C \cs_end: {#3}{#5} }
               { \cs:w mhchem@arrow@#1M \cs_end: {#3}{#5} }
           }
         { M }
@@ -903,15 +1081,26 @@
 
 %%% Arrow compositions with text or chemistry
 \newtoks\mhchem@arrow@params%
+\ExplSyntaxOn
 \def\mhchem@arrow@setParamsT#1#2{%
   \mhchem@arrow@params={}%
   \@ifempty{#1}%
     {\mhchem@appendToks{\mhchem@arrow@params}{{}}}%
-    {\mhchem@appendToks{\mhchem@arrow@params}{{\text{#1}}}}%
+    {\mhchem@appendToks{\mhchem@arrow@params}{{\__mhchem_output_escapeFromMathToText:n{#1}}}}%
+  \@ifempty{#2}%
+    {\mhchem@appendToks{\mhchem@arrow@params}{{}}}%
+    {\mhchem@appendToks{\mhchem@arrow@params}{{\__mhchem_output_escapeFromMathToText:n{#2}}}}%
+}%
+\def\mhchem@arrow@setParamst#1#2{%
+  \mhchem@arrow@params={}%
+  \@ifempty{#1}%
+    {\mhchem@appendToks{\mhchem@arrow@params}{{}}}%
+    {\mhchem@appendToks{\mhchem@arrow@params}{{\__mhchem_cg_escapeFromMathToTextOrFaketext:n{#1}}}}%
   \@ifempty{#2}%
     {\mhchem@appendToks{\mhchem@arrow@params}{{}}}%
-    {\mhchem@appendToks{\mhchem@arrow@params}{{\text{#2}}}}%
+    {\mhchem@appendToks{\mhchem@arrow@params}{{\__mhchem_cg_escapeFromMathToTextOrFaketext:n{#2}}}}%
 }%
+\ExplSyntaxOff
 \def\mhchem@arrow@setParamsC#1#2{%
   \mhchem@arrow@params={}%
   \@ifempty{#1}%
@@ -924,43 +1113,64 @@
 \newcommand*\mhchem@arrow@yieldsT[2]{%
   \mhchem@arrow@setParamsT{#1}{#2}%
   \expandafter\mhchem@arrow@yieldsM\the\mhchem@arrow@params}%
+\newcommand*\mhchem@arrow@yieldst[2]{%
+  \mhchem@arrow@setParamst{#1}{#2}%
+  \expandafter\mhchem@arrow@yieldsM\the\mhchem@arrow@params}%
 \newcommand*\mhchem@arrow@yieldsC[2]{%
   \mhchem@arrow@setParamsC{#1}{#2}%
   \expandafter\mhchem@arrow@yieldsM\the\mhchem@arrow@params}%
 \newcommand*\mhchem@arrow@yieldsLeftT[2]{%
   \mhchem@arrow@setParamsT{#1}{#2}%
   \expandafter\mhchem@arrow@yieldsLeftM\the\mhchem@arrow@params}%
+\newcommand*\mhchem@arrow@yieldsLeftt[2]{%
+  \mhchem@arrow@setParamst{#1}{#2}%
+  \expandafter\mhchem@arrow@yieldsLeftM\the\mhchem@arrow@params}%
 \newcommand*\mhchem@arrow@yieldsLeftC[2]{%
   \mhchem@arrow@setParamsC{#1}{#2}%
   \expandafter\mhchem@arrow@yieldsLeftM\the\mhchem@arrow@params}%
 \newcommand*\mhchem@arrow@yieldsLeftRightT[2]{%
   \mhchem@arrow@setParamsT{#1}{#2}%
   \expandafter\mhchem@arrow@yieldsLeftRightM\the\mhchem@arrow@params}%
+\newcommand*\mhchem@arrow@yieldsLeftRightt[2]{%
+  \mhchem@arrow@setParamst{#1}{#2}%
+  \expandafter\mhchem@arrow@yieldsLeftRightM\the\mhchem@arrow@params}%
 \newcommand*\mhchem@arrow@yieldsLeftRightC[2]{%
   \mhchem@arrow@setParamsC{#1}{#2}%
   \expandafter\mhchem@arrow@yieldsLeftRightM\the\mhchem@arrow@params}%
 \newcommand*\mhchem@arrow@mesomerismT[2]{%
   \mhchem@arrow@setParamsT{#1}{#2}%
   \expandafter\mhchem@arrow@mesomerismM\the\mhchem@arrow@params}%
+\newcommand*\mhchem@arrow@mesomerismt[2]{%
+  \mhchem@arrow@setParamst{#1}{#2}%
+  \expandafter\mhchem@arrow@mesomerismM\the\mhchem@arrow@params}%
 \newcommand*\mhchem@arrow@mesomerismC[2]{%
   \mhchem@arrow@setParamsC{#1}{#2}%
   \expandafter\mhchem@arrow@mesomerismM\the\mhchem@arrow@params}%
-\newcommand*{\mhchem@arrow@equilibriumT}[2]{%
+\newcommand*\mhchem@arrow@equilibriumT[2]{%
   \mhchem@arrow@setParamsT{#1}{#2}%
   \expandafter\mhchem@arrow@equilibriumM\the\mhchem@arrow@params}%
-\newcommand*{\mhchem@arrow@equilibriumC}[2]{%
+\newcommand*\mhchem@arrow@equilibriumt[2]{%
+  \mhchem@arrow@setParamst{#1}{#2}%
+  \expandafter\mhchem@arrow@equilibriumM\the\mhchem@arrow@params}%
+\newcommand*\mhchem@arrow@equilibriumC[2]{%
   \mhchem@arrow@setParamsC{#1}{#2}%
   \expandafter\mhchem@arrow@equilibriumM\the\mhchem@arrow@params}%
-\newcommand*{\mhchem@arrow@equilibriumRightT}[2]{%
+\newcommand*\mhchem@arrow@equilibriumRightT[2]{%
   \mhchem@arrow@setParamsT{#1}{#2}%
   \expandafter\mhchem@arrow@equilibriumRightM\the\mhchem@arrow@params}%
-\newcommand*{\mhchem@arrow@equilibriumRightC}[2]{%
+\newcommand*\mhchem@arrow@equilibriumRightt[2]{%
+  \mhchem@arrow@setParamst{#1}{#2}%
+  \expandafter\mhchem@arrow@equilibriumRightM\the\mhchem@arrow@params}%
+\newcommand*\mhchem@arrow@equilibriumRightC[2]{%
   \mhchem@arrow@setParamsC{#1}{#2}%
   \expandafter\mhchem@arrow@equilibriumRightM\the\mhchem@arrow@params}%
-\newcommand*{\mhchem@arrow@equilibriumLeftT}[2]{%
+\newcommand*\mhchem@arrow@equilibriumLeftT[2]{%
   \mhchem@arrow@setParamsT{#1}{#2}%
   \expandafter\mhchem@arrow@equilibriumLeftM\the\mhchem@arrow@params}%
-\newcommand*{\mhchem@arrow@equilibriumLeftC}[2]{%
+\newcommand*\mhchem@arrow@equilibriumLeftt[2]{%
+  \mhchem@arrow@setParamst{#1}{#2}%
+  \expandafter\mhchem@arrow@equilibriumLeftM\the\mhchem@arrow@params}%
+\newcommand*\mhchem@arrow@equilibriumLeftC[2]{%
   \mhchem@arrow@setParamsC{#1}{#2}%
   \expandafter\mhchem@arrow@equilibriumLeftM\the\mhchem@arrow@params}%
 
@@ -1102,88 +1312,6 @@
   \end{tikzpicture}%
 }%
 
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%   bonds   %%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-
-\newlength\mhchem@bondwidth%
-\newlength\mhchem@bondheight%
-\newlength\mhchem@smallbondwidth@tmpA%
-\newlength\mhchem@smallbondwidth@tmpB%
-\newlength\mhchem@smallbondwidth%
-
-\def\mhchem@setbondwidth{%
-  \setlength\mhchem@bondwidth{\widthof{\sbond}}%
-  \setlength\mhchem@bondheight{\heightof{\sbond}}%
-  \setlength\mhchem@smallbondwidth@tmpA{%
-    \mhchem@bondwidth-\mhchem@option@minussidebearingleft-\mhchem@option@minussidebearingright}%
-  \setlength\mhchem@smallbondwidth@tmpB{%
-    \widthof{\sbond\sbond\sbond}-\mhchem@option@minussidebearingleft-%
-    \mhchem@option@minussidebearingright}%
-  \setlength\mhchem@smallbondwidth{\mhchem@bondwidth*%
-    \ratio{\mhchem@smallbondwidth@tmpA}{\mhchem@smallbondwidth@tmpB}}%
-}
-\def\mhchem@halfbond{\rlap{\hspace{\mhchem@option@minussidebearingleft}%
-                     \resizebox{\mhchem@smallbondwidth}{\mhchem@bondheight}{\sbond}\unskip%
-                     \resizebox{\mhchem@smallbondwidth}{\mhchem@bondheight}{\sbond}%
-                     \resizebox{\mhchem@smallbondwidth}{\mhchem@bondheight}{\sbond}}%
-                     \phantom{\sbond}}%
-\ExplSyntaxOn
-\char_set_catcode_letter:n { 126 } % tilde
-\cs_new_protected:Npn \mhchem@bond #1
-  {
-    \str_case:nnn {#1}
-      {
-        { - } { \sbond }
-        { 1 } { \sbond }
-        { = } { \dbond }
-        { 2 } { \dbond }
-        { ## } { \tbond }
-        { 3 } { \tbond }
-        { ~ }
-          {
-            \mhchem@setbondwidth
-            \mhchem@halfbond
-          }
-        { ~- }
-          {
-            \mhchem@setbondwidth
-            \rlap{\protect\raisebox{.2ex}{\mhchem@halfbond}}
-            \protect\raisebox{-.2ex}{\sbond}
-          }
-        { ~-- }
-          {
-            \mhchem@setbondwidth
-            \rlap{\protect\raisebox{.4ex}{\mhchem@halfbond}}
-            \rlap{\sbond}
-            \protect\raisebox{-.4ex}{\sbond}
-          }
-        { ~= }
-          {
-            \mhchem@setbondwidth
-            \rlap{\protect\raisebox{.4ex}{\mhchem@halfbond}}
-            \rlap{\sbond}
-            \protect\raisebox{-.4ex}{\sbond}
-          }
-        { -~- }
-          {
-            \mhchem@setbondwidth
-            \rlap{\protect\raisebox{.4ex}{\sbond}}
-            \rlap{\mhchem@halfbond}
-            \protect\raisebox{-.4ex}{\sbond}
-          }
-        { ... } { {\cdot}{\cdot}{\cdot} }
-        { .... } { {\cdot}{\cdot}{\cdot}{\cdot} }
-        { -> } { {\rightarrow} }
-        { <- } { {\leftarrow} }
-      }
-      {
-        %todo Tilde is not a space anymore, here
-        \PackageError{mhchem}{Unknown~bond~type~in~\string\bond~(#1)}%
-      }
-  }
-\ExplSyntaxOff  % end of Expl with tilde
-
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%   loop helpers   %%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -1206,21 +1334,32 @@
   }
 
 \cs_new_protected:Npn
-  \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:NNn #1#2#3
+  \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:nNn #1#2#3
   {
     \__mhchem_cf_outputAndReset:
-    \tl_put_right:Nn \__mhchem_cf_result_tl { \mhchem@mathOrText{#3} }
-    \tl_set:Nn \__mhchem_cf_state_tl {#1}
+    \tl_put_right:Nn \l__mhchem_cf_element_tl { \__mhchem_output_withFont:n {#3} }
+    \__mhchem_cf_outputRawElementAndReset:
+    \tl_set:Nn \l__mhchem_cf_state_tl {#1}
     #2
   }
 \cs_new_protected:Npn
-  \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:NNn #1#2#3#4
+  \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:nnNn #1#2#3#4
   {
     \__mhchem_cf_outputAndReset:
-    \tl_put_right:Nn \__mhchem_cf_result_tl {#1}
-    \tl_set:Nn \__mhchem_cf_state_tl {#2}
+    \tl_put_right:Nn \l__mhchem_cf_element_tl {#1}
+    \__mhchem_cf_outputRawElementAndReset:
+    \tl_set:Nn \l__mhchem_cf_state_tl {#2}
     #3
   }
+\cs_new_protected:Npn
+  \__mhchem_loopHelper_outputAndReset_append_appendNextGroupToResult:nNnn #1#2#3
+  {
+    \__mhchem_cf_outputAndReset:
+    \tl_put_right:Nn \l__mhchem_cf_element_tl {#1}
+    \tl_put_right:Nn \l__mhchem_cf_element_tl {{#3}}
+    \__mhchem_cf_outputRawElementAndReset:
+    #2
+  }
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%   \cf   %%%%%%%%%%
@@ -1230,46 +1369,46 @@
   \__mhchem_cf:nn {#1} {#2}
 }
 
-\bool_new:N \__mhchem_cf_startedWithBond_bool
-
-\tl_new:N \__mhchem_cf_state_tl
-\tl_new:N \__mhchem_cf_presup_tl
-\tl_new:N \__mhchem_cf_presub_tl
-\tl_new:N \__mhchem_cf_presupState_tl
-\tl_new:N \__mhchem_cf_presubState_tl
-\tl_new:N \__mhchem_cf_element_tl
-\tl_new:N \__mhchem_cf_supA_tl
-\tl_new:N \__mhchem_cf_sub_tl
-\tl_new:N \__mhchem_cf_sup_tl
-\tl_new:N \__mhchem_cf_supState_tl
-\tl_new:N \__mhchem_cf_subState_tl
+\bool_new:N \l__mhchem_cf_startedWithBond_bool
+
+\tl_new:N \l__mhchem_cf_state_tl
+\tl_new:N \l__mhchem_cf_presup_tl
+\tl_new:N \l__mhchem_cf_presub_tl
+\tl_new:N \l__mhchem_cf_presupState_tl
+\tl_new:N \l__mhchem_cf_presubState_tl
+\tl_new:N \l__mhchem_cf_element_tl
+\tl_new:N \l__mhchem_cf_sub_tl
+\tl_new:N \l__mhchem_cf_sup_tl
+\tl_new:N \l__mhchem_cf_supState_tl
+\tl_new:N \l__mhchem_cf_subState_tl
+\tl_new:N \l__mhchem_cf_lastElement_tl
 \cs_new_protected:Npn \__mhchem_cf_resetOutput:
   {
-    \tl_clear:N \__mhchem_cf_presup_tl
-    \tl_clear:N \__mhchem_cf_presub_tl
-    \tl_set:Nn \__mhchem_cf_presupState_tl { - }
-    \tl_set:Nn \__mhchem_cf_presubState_tl { - }
-    \tl_clear:N \__mhchem_cf_element_tl
-    \tl_clear:N \__mhchem_cf_supA_tl
-    \tl_clear:N \__mhchem_cf_sub_tl
-    \tl_clear:N \__mhchem_cf_sup_tl
-    \tl_set:Nn \__mhchem_cf_supState_tl { - }
-    \tl_set:Nn \__mhchem_cf_subState_tl { - }
+    \tl_clear:N \l__mhchem_cf_presup_tl
+    \tl_clear:N \l__mhchem_cf_presub_tl
+    \tl_set:Nn \l__mhchem_cf_presupState_tl { - }
+    \tl_set:Nn \l__mhchem_cf_presubState_tl { - }
+    \tl_clear:N \l__mhchem_cf_element_tl
+    \tl_clear:N \l__mhchem_cf_sub_tl
+    \tl_clear:N \l__mhchem_cf_sup_tl
+    \tl_set:Nn \l__mhchem_cf_supState_tl { - }
+    \tl_set:Nn \l__mhchem_cf_subState_tl { - }
   }
 
-\bool_new:N \__mhchem_cf_cfActive_bool
-\bool_set_false:N \__mhchem_cf_cfActive_bool
+\bool_new:N \l__mhchem_cf_cfActive_bool
+\bool_set_false:N \l__mhchem_cf_cfActive_bool
+\tl_new:N \l__mhchem_cf_result_tl
 \cs_new_protected:Npn \__mhchem_cf:nn #1#2
   {
     \group_begin:
-    \def\sbond{{\ensuremath{-}}}
-    \int_compare:nTF { 2 = \__mhchem_option_version_int }
+    \let\sbond\__mhchem_output_sbond:
+    \int_compare:nTF { 2 = \l__mhchem_option_version_int }
       {
         \let\bond\sbond
       }
     % else
       {
-        \int_compare:nT { \__mhchem_option_version_int > 2 }
+        \int_compare:nT { \l__mhchem_option_version_int > 2 }
           {
             \def\bond{\mhchem@bond}
           }
@@ -1278,40 +1417,50 @@
     \def\tbond{\rlap{\protect\raisebox{.4ex}{\sbond}}
       \rlap{\sbond}\protect\raisebox{-.4ex}{\sbond}}
     \def\hyphen{\mhchem@hyphen}
-    \bool_if:NF \__mhchem_ce_ceActive_bool {
-      \bool_if:NF \__mhchem_cf_cfActive_bool
+    \bool_if:NF \l__mhchem_ce_ceActive_bool {
+      \bool_if:NF \l__mhchem_cf_cfActive_bool
         {
-          \bool_set_true:N \__mhchem_cf_cfActive_bool
-          \__mhchem_defMathOrText:
+          \bool_set_true:N \l__mhchem_cf_cfActive_bool
+          \__mhchem_output_defMathOrText:
         }
       }
-    \tl_set:Nn \__mhchem_cf_state_tl { s }
-    \bool_set_false:N \__mhchem_cf_startedWithBond_bool
+    \tl_set:Nn \l__mhchem_cf_state_tl { s }
+    \bool_set_false:N \l__mhchem_cf_startedWithBond_bool
     \__mhchem_cf_resetOutput:
-    \tl_clear_new:N \__mhchem_cf_result_tl
-    \__mhchem_cf_loop: #2 \q_recursion_stop
-    \str_if_eq:nnTF {#1} {}
-      { \ensuremath{\tl_use:N \__mhchem_cf_result_tl} }
-      { \ensuremath{\overset{#1}{\tl_use:N \__mhchem_cf_result_tl}} }
+    \tl_set:Nn \l__mhchem_cf_result_tl {#2}
+    \regex_replace_once:nnNTF
+      { \A [nmpx] \Z } { \c{__mhchem_output_withFont:n}\cB[ \c{__mhchem_cg_itshape:n}\cB[ \0 \cE]\cE] } \l__mhchem_cf_result_tl
+      {}
+      {
+        \tl_clear:N \l__mhchem_cf_result_tl
+        \__mhchem_cf_loop: #2 \q_recursion_stop
+      }
+      \str_if_eq:nnTF {#1} {}
+        { \ensuremath{\tl_use:N \l__mhchem_cf_result_tl} }
+        { \ensuremath{\overset{#1}{\tl_use:N \l__mhchem_cf_result_tl}} }
     \group_end:
   }
+\tl_new:N \l__mhchem_cf_loop_tmpa_l
+\tl_new:N \l__mhchem_cf_loop_tmpb_l
+\tl_new:N \l__mhchem_cf_loop_tmpc_l
+\tl_new:N \l__mhchem_cf_loop_tmpd_l
 \cs_new_protected:Npn \__mhchem_cf_loop:
   {
     \peek_meaning_remove:NTF \q_recursion_stop
       {
-        \str_case:Vnn \__mhchem_cf_state_tl
+        \str_case:Vnn \l__mhchem_cf_state_tl
           {
             { - }
               {
-                \bool_if:NTF \__mhchem_cf_startedWithBond_bool
+                \bool_if:NTF \l__mhchem_cf_startedWithBond_bool
                   {
                     \__mhchem_cf_outputAndReset:
-                    \tl_put_right:Nn \__mhchem_cf_result_tl { \sbond }
+                    \__mhchem_cf_outputRawElementAndReset:n { \sbond }
                   }
-                  { \tl_put_right:Nn \__mhchem_cf_sup_tl { - } }
+                  { \tl_put_right:Nn \l__mhchem_cf_sup_tl { - } }
               }
             { 1 }
-              { \tl_set:Nn \__mhchem_cf_state_tl {9} }
+              { \tl_set:Nn \l__mhchem_cf_state_tl {9} }
           }
           {}
         \__mhchem_cf_outputAndReset:
@@ -1320,37 +1469,62 @@
       { \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop: }{
     \peek_meaning:NTF \protect
       { \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop: }{
-    \str_case:Vnn \__mhchem_cf_state_tl
+    \str_case:Vnn \l__mhchem_cf_state_tl
       {
         { - }
           {
             \__mhchem_cf_outputAndReset:
-            \tl_put_right:Nn \__mhchem_cf_result_tl {\sbond}
-            \tl_set:Nn \__mhchem_cf_state_tl { a }
+            \regex_match:nVTF
+              { \A (n|\c{eta}|\c{mu}|\c{kappa}|\c{__mhchem_cg_withinMathTokens:n}\cB.n\cE.|\d+|\(\+\)) \Z }
+              \l__mhchem_cf_lastElement_tl
+              {
+                \__mhchem_cf_outputRawElementAndReset:n
+                  { \__mhchem_cg_escapeFromMathToTextOrFaketext:n { - } }
+              }
+              {
+                \__mhchem_cf_outputRawElementAndReset:n { \sbond }
+              }
+            \tl_set:Nn \l__mhchem_cf_state_tl { a }
             \__mhchem_cf_loop:
           }
+        { ( }
+          {
+            \__mhchem_regex_peek:nTF { [0-9] }
+              {
+                \tl_set:Nn \l__mhchem_cf_state_tl { 1 }
+                \__mhchem_loopHelper_appendNextToken:NNn
+                  \l__mhchem_cf_element_tl
+                  \__mhchem_cf_loop:
+              }
+            % else
+              {
+                \__mhchem_cf_outputAndReset:
+                \tl_set:Nn \l__mhchem_cf_state_tl { s }
+                \__mhchem_cf_loop:
+              }
+          }
         { s }
           {
             \peek_charcode:NTF -
               {
                 \__mhchem_cf_outputAndReset:
-                \int_compare:nTF { \__mhchem_option_version_int > 1 }
+                \int_compare:nTF { \l__mhchem_option_version_int > 1 }
                   {
-                    \tl_set:Nn \__mhchem_cf_state_tl { - }
-                    \bool_set_true:N \__mhchem_cf_startedWithBond_bool
+                    \tl_set:Nn \l__mhchem_cf_state_tl { - }
+                    \bool_set_true:N \l__mhchem_cf_startedWithBond_bool
                     \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
                   }
                 % else
                   {
-                    \tl_set:Nn \__mhchem_cf_state_tl { a }
-                    \tl_put_right:Nn \__mhchem_cf_sup_tl { - }  % z. B. \cmath{mu}-Cl
+                    \tl_set:Nn \l__mhchem_cf_state_tl { a }
+                    \tl_put_right:Nn \l__mhchem_cf_sup_tl { - }
                     \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
                   }
               }{
             \peek_charcode:NTF =
               {
                 \__mhchem_cf_outputAndReset:
-                \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:NNn
+                \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:nnNn
                   { \dbond }
                   { s }
                   \__mhchem_cf_loop:
@@ -1358,1479 +1532,1428 @@
             \peek_charcode:NTF ##
               {
                 \__mhchem_cf_outputAndReset:
-                \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:NNn
+                \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:nnNn
                   { \tbond }
                   { s }
                   \__mhchem_cf_loop:
               }{
             \peek_charcode:NTF ^
               {
-                \str_if_eq:VnF \__mhchem_cf_presupState_tl { - }
+                \str_if_eq:VnF \l__mhchem_cf_presupState_tl { - }
                   { \__mhchem_cf_outputAndReset: }
-                \tl_set:Nn \__mhchem_cf_presupState_tl { d }
-                \tl_set:Nn \__mhchem_cf_state_tl { p }
+                \tl_set:Nn \l__mhchem_cf_presupState_tl { d }
+                \tl_set:Nn \l__mhchem_cf_state_tl { p }
                 \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
               }{
             \peek_charcode:NTF _
               {
-                \str_if_eq:VnF \__mhchem_cf_presubState_tl { - }
+                \str_if_eq:VnF \l__mhchem_cf_presubState_tl { - }
                   { \__mhchem_cf_outputAndReset: }
-                \tl_set:Nn \__mhchem_cf_presubState_tl { d }
-                \tl_set:Nn \__mhchem_cf_state_tl { q }
+                \tl_set:Nn \l__mhchem_cf_presubState_tl { d }
+                \tl_set:Nn \l__mhchem_cf_state_tl { q }
                 \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
               }{
             \peek_charcode:NTF `
               {
-                \int_compare:nTF { \__mhchem_option_version_int < 4 }
+                \int_compare:nTF { \l__mhchem_option_version_int < 4 }
                   {
-                    \str_if_eq:VnF \__mhchem_cf_presupState_tl { - }
+                    \str_if_eq:VnF \l__mhchem_cf_presupState_tl { - }
                       { \__mhchem_cf_outputAndReset: }
-                    \tl_set:Nn \__mhchem_cf_presupState_tl { rm }
-                    \tl_set:Nn \__mhchem_cf_state_tl { p }
+                    \tl_set:Nn \l__mhchem_cf_presupState_tl { rm }
+                    \tl_set:Nn \l__mhchem_cf_state_tl { p }
                     \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
                   }
                 % else
                   {
-                    \tl_set:Nn \__mhchem_cf_state_tl { a }
+                    \tl_set:Nn \l__mhchem_cf_state_tl { a }
                     \__mhchem_loopHelper_appendNextToken:NNn
-                      \__mhchem_cf_element_tl
+                      \l__mhchem_cf_element_tl
                       \__mhchem_cf_loop:
                   }
               }{
             \peek_charcode:NTF ,
               {
-                \int_compare:nTF { \__mhchem_option_version_int < 4 }
+                \int_compare:nTF { \l__mhchem_option_version_int < 4 }
                   {
-                    \str_if_eq:VnF \__mhchem_cf_presubState_tl { - }
+                    \str_if_eq:VnF \l__mhchem_cf_presubState_tl { - }
                       { \__mhchem_cf_outputAndReset: }
-                    \tl_set:Nn \__mhchem_cf_presubState_tl { rm }
-                    \tl_set:Nn \__mhchem_cf_state_tl { q }
+                    \tl_set:Nn \l__mhchem_cf_presubState_tl { rm }
+                    \tl_set:Nn \l__mhchem_cf_state_tl { q }
                     \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
                   }
                 % else
                   {
                     \__mhchem_cf_outputAndReset:
-                    \tl_set:Nn \__mhchem_cf_state_tl { 1 }
+                    \tl_set:Nn \l__mhchem_cf_state_tl { 1 }
                     \__mhchem_cf_loop:
                   }
               }{
-            \peek_charcode:NTF .
-              {
-
-                \__mhchem_cf_outputAndReset:
-                \tl_set:Nn \__mhchem_cf_state_tl { 1 }
-                \__mhchem_cf_loop:
-              }{
             \peek_charcode:NTF *
               {
-                \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:NNn
-                  { \mhchem@mathOrText@ii{{}\cdot{}}{\mhchem@option@textcdot} }
+                \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:nnNn
+                  { \__mhchem_output_additionCompound: }
                   { s }
                   \__mhchem_cf_loop:
               }{
             \peek_charcode:NTF +
               {
-                \str_if_eq:VnF \__mhchem_cf_presupState_tl { - }
+                \str_if_eq:VnF \l__mhchem_cf_presupState_tl { - }
                   { \__mhchem_cf_outputAndReset: }
-                \tl_set:Nn \__mhchem_cf_presupState_tl { d }
-                \tl_set:Nn \__mhchem_cf_state_tl { p }
+                \tl_set:Nn \l__mhchem_cf_presupState_tl { d }
+                \tl_set:Nn \l__mhchem_cf_state_tl { p }
                 \__mhchem_cf_loop:
               }{
-            \peek_charcode:NTF |
-              {
-                \let\mhchem@cf@action\mhchem@cf@switchState
-              }{
             \peek_charcode:NTF (
               {
-                \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:NNn
-                  { s }
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF )
-              {
-                \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:NNn
-                  { a }
+                \__mhchem_cf_outputAndReset:
+                \tl_set:Nn \l__mhchem_cf_state_tl { ( }
+                \__mhchem_loopHelper_appendNextToken:NNn
+                  \l__mhchem_cf_element_tl
                   \__mhchem_cf_loop:
               }{
             \peek_charcode:NTF [
               {
-                \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:NNn
+                \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:nNn
                   { s }
                   \__mhchem_cf_loop:
               }{
-            \peek_charcode:NTF ]
+            \__mhchem_regex_peek:nTF { [ \) \] \/ ] }
               {
-                \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:NNn
+                \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:nNn
                   { a }
                   \__mhchem_cf_loop:
               }{
             \peek_catcode:NTF \mhchem@macro
               {
                 \__mhchem_cf_outputAndReset:
-                \tl_set:Nn \__mhchem_cf_state_tl { c }
+                \tl_set:Nn \l__mhchem_cf_state_tl { c }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_result_tl
+                  \l__mhchem_cf_element_tl
                   \__mhchem_cf_loop:
               }{
             \peek_catcode:NTF a
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { a }
+                \tl_set:Nn \l__mhchem_cf_state_tl { a }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
+                  \l__mhchem_cf_element_tl
                   \__mhchem_cf_loop:
               }{
-            \peek_catcode:NTF 1
+            \__mhchem_regex_peek:nTF { [ 0-9 . ] }
               {
                 \__mhchem_cf_outputAndReset:
-                \tl_set:Nn \__mhchem_cf_state_tl { 1 }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
+                \tl_set:Nn \l__mhchem_cf_state_tl { 1 }
+                \__mhchem_cf_loop:
               }{
             \peek_catcode:NTF \c_group_begin_token
               {
-                  \__mhchem_cf_outputAndReset:
-                  \__mhchem_loopHelper_appendNextToken:NNn
-                    \__mhchem_cf_result_tl
-                    \__mhchem_cf_loop:
+                \__mhchem_cf_outputAndReset:
+                \int_compare:nTF { \l__mhchem_option_version_int < 4 }
+                  {
+                    \__mhchem_loopHelper_outputAndReset_append_appendNextGroupToResult:nNnn
+                      {}
+                      \__mhchem_cf_loop:
+                  }
+                % else
+                  {
+                    \tl_set:Nn \l__mhchem_cf_state_tl { a }
+                    \__mhchem_loopHelper_appendNextGroup_prefix_ifEmpty:NnnNn
+                      \l__mhchem_cf_element_tl
+                      { \__mhchem_cg_escapeFromMathToTextOrFaketext:n }
+                      { \tl_set:Nn \l__mhchem_cf_state_tl { s } }
+                      \__mhchem_cf_loop:
+                  }
               }{
             \peek_catcode_remove:NTF \c_math_toggle_token
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { a }
-                \__mhchem_loopHelper_appendMathB:NNw
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
+                \tl_set:Nn \l__mhchem_cf_state_tl { a }
+                \__mhchem_loopHelper_appendMathB:nn
+                  { l__mhchem_cf_element_tl }
+                  { __mhchem_cf_loop: }
               }
             % else
               { \msg_error:nnn { mhchem } { cf / unexpected-input } }
-            }}}}}}}}}}}}}}}}}}}
+            }}}}}}}}}}}}}}}}
           }
         { c }
           {
-            \peek_catcode:NTF \c_group_begin_token
+            \regex_match:nVTF
+              { \A [\c{alpha}\c{beta}\c{gamma}\c{delta}\c{epsilon}\c{zeta}\c{eta}\c{theta}\c{iota}\c{kappa}\c{lambda}\c{mu}\c{nu}\c{xi}\c{omicron}\c{pi}\c{rho}\c{sigma}\c{tau}\c{upsilon}\c{phi}\c{chi}\c{psi}\c{omega}\c{Alpha}\c{Beta}\c{Gamma}\c{Delta}\c{Epsilon}\c{Zeta}\c{Eta}\c{Theta}\c{Iota}\c{Kappa}\c{Lambda}\c{Mu}\c{Nu}\c{Xi}\c{Omicron}\c{Pi}\c{Rho}\c{Sigma}\c{Tau}\c{Upsilon}\c{Phi}\c{Chi}\c{Psi}\c{Omega}] \Z }
+              \l__mhchem_cf_element_tl
               {
-                \__mhchem_loopHelper_appendNextGroup:NNn
-                  \__mhchem_cf_result_tl
-                  \__mhchem_cf_loop:
+                \tl_set:Nn \l__mhchem_cf_state_tl { a }
+                \__mhchem_cf_loop:
               }
-            % else
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { a }
-                \__mhchem_cf_loop:
+                \peek_catcode:NTF \c_group_begin_token
+                  {
+                    \__mhchem_loopHelper_appendNextGroup:NNn
+                      \l__mhchem_cf_element_tl
+                      \__mhchem_cf_loop:
+                  }
+                % else
+                  {
+                    \__mhchem_cf_outputAndReset:
+                    \tl_set:Nn \l__mhchem_cf_state_tl { a }
+                    \__mhchem_cf_loop:
+                  }
               }
           }
         { 1 }
           {
-            \peek_charcode:NTF 1
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
-              }
-              {
-            \peek_charcode:NTF 2
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
-              }
-              {
-            \peek_charcode:NTF 3
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
-              }
-              {
-            \peek_charcode:NTF 4
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
-              }
-              {
-            \peek_charcode:NTF 5
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
-              }
-              {
-            \peek_charcode:NTF 6
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
-              }
-              {
-            \peek_charcode:NTF 7
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
-              }
-              {
-            \peek_charcode:NTF 8
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
-              }
-              {
-            \peek_charcode:NTF 9
+            \__mhchem_regex_peek:nTF { [ 0-9 \) \. \/ ] }
               {
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
+                  \l__mhchem_cf_element_tl
                   \__mhchem_cf_loop:
-              }
-              {
-            \peek_charcode:NTF 0
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
-              }
-              {
-            \peek_charcode:NTF .
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
-              }
-              {
+              }{
             \peek_charcode:NTF ,
               {
-                \tl_put_right:Nn \__mhchem_cf_element_tl { {,} }
+                \tl_put_right:Nn \l__mhchem_cf_element_tl { \__mhchem_output_commaDecimal: }
                 \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
-              }
-              {
-            \peek_charcode:NTF /
+              }{
+            \peek_charcode:NTF -
               {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
+                \tl_set:Nn \l__mhchem_cf_state_tl { - }
+                \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
               }
             % else
               {
                 \__mhchem_cf_outputAndReset:
-                \tl_set:Nn \__mhchem_cf_state_tl { s }
+                \tl_set:Nn \l__mhchem_cf_state_tl { s }
                 \__mhchem_cf_loop:
               }
-            }}}}}}}}}}}}
+            }}
           }
         { a }
           {
             \peek_charcode:NTF -
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { - }
+                \tl_set:Nn \l__mhchem_cf_state_tl { - }
                 \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
               }{
             \peek_charcode:NTF =
               {
-                \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:NNn
+                \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:nnNn
                   { \dbond }
                   { s }
                   \__mhchem_cf_loop:
               }{
             \peek_charcode:NTF ##
               {
-                \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:NNn
+                \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:nnNn
                   { \tbond }
                   { s }
                   \__mhchem_cf_loop:
               }{
             \peek_charcode:NTF ^
               {
-                \str_if_eq:VnF \__mhchem_cf_supState_tl { - }
+                \str_if_eq:VnF \l__mhchem_cf_supState_tl { - }
                   { \__mhchem_cf_outputAndReset: }
-                \str_if_eq:VnTF \__mhchem_cf_subState_tl { - }
-                  { \tl_set:Nn \__mhchem_cf_supState_tl { kv } }
-                  { \tl_set:Nn \__mhchem_cf_supState_tl { d } }
-                \tl_set:Nn \__mhchem_cf_state_tl { e }
+                \str_if_eq:VnTF \l__mhchem_cf_subState_tl { - }
+                  { \tl_set:Nn \l__mhchem_cf_supState_tl { kv } }
+                  { \tl_set:Nn \l__mhchem_cf_supState_tl { d } }
+                \tl_set:Nn \l__mhchem_cf_state_tl { e }
                 \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
               }{
             \peek_charcode:NTF _
               {
-                \str_if_eq:VnF \__mhchem_cf_subState_tl { - }
+                \str_if_eq:VnF \l__mhchem_cf_subState_tl { - }
                   { \__mhchem_cf_outputAndReset: }
-                \tl_set:Nn \__mhchem_cf_subState_tl { d }
-                \tl_set:Nn \__mhchem_cf_state_tl { f }
+                \tl_set:Nn \l__mhchem_cf_subState_tl { d }
+                \tl_set:Nn \l__mhchem_cf_state_tl { f }
                 \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
               }{
             \peek_charcode:NTF `
               {
-                \int_compare:nTF { \__mhchem_option_version_int < 4 }
+                \int_compare:nTF { \l__mhchem_option_version_int < 4 }
                   {
-                    \str_if_eq:VnF \__mhchem_cf_supState_tl { - }
+                    \str_if_eq:VnF \l__mhchem_cf_supState_tl { - }
                       { \__mhchem_cf_outputAndReset: }
-                    \tl_set:Nn \__mhchem_cf_supState_tl { rm }
-                    \tl_set:Nn \__mhchem_cf_state_tl { e }
+                    \tl_set:Nn \l__mhchem_cf_supState_tl { rm }
+                    \tl_set:Nn \l__mhchem_cf_state_tl { e }
                     \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
                   }
                 % else
                   {
-                    \str_if_eq:VnF \__mhchem_cf_supState_tl { - }
+                    \str_if_eq:VnF \l__mhchem_cf_supState_tl { - }
                       { \__mhchem_cf_outputAndReset: }
-                    \str_if_eq:VnF \__mhchem_cf_subState_tl { - }
+                    \str_if_eq:VnF \l__mhchem_cf_subState_tl { - }
                       { \__mhchem_cf_outputAndReset: }
                     \__mhchem_loopHelper_appendNextToken:NNn
-                      \__mhchem_cf_element_tl
+                      \l__mhchem_cf_element_tl
                       \__mhchem_cf_loop:
                   }
               }{
             \peek_charcode:NTF ,
               {
-                \int_compare:nTF { \__mhchem_option_version_int < 4 }
+                \int_compare:nTF { \l__mhchem_option_version_int < 4 }
                   {
-                    \str_if_eq:VnF \__mhchem_cf_subState_tl { - }
+                    \str_if_eq:VnF \l__mhchem_cf_subState_tl { - }
                       { \__mhchem_cf_outputAndReset: }
-                    \tl_set:Nn \__mhchem_cf_subState_tl { rm }
-                    \tl_set:Nn \__mhchem_cf_state_tl { f }
+                    \tl_set:Nn \l__mhchem_cf_subState_tl { rm }
+                    \tl_set:Nn \l__mhchem_cf_state_tl { f }
                     \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
                   }
                 % else
                   {
                     \__mhchem_cf_outputAndReset:
-                    \tl_put_right:Nn \__mhchem_cf_result_tl { {,} }
-                    \__mhchem_loopHelper_ignoreNextToken:Nn
-                      \__mhchem_cf_loop:
+                    \__mhchem_cf_outputRawElementAndReset:n
+                      { \__mhchem_output_commaEnumeration: }
+                    \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
                   }
               }{
-            \peek_charcode:NTF .
+            \__mhchem_regex_peek:nTF { [ \. \* ] }
               {
-                \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:NNn
-                  { \mhchem@mathOrText@ii{{}\cdot{}}{\mhchem@option@textcdot} }
-                  { s }
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF *
-              {
-                \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:NNn
-                  { \mhchem@mathOrText@ii{{}\cdot{}}{\mhchem@option@textcdot} }
+                \__mhchem_loopHelper_outputAndReset_appendToResult_setState_useNone:nnNn
+                  { \__mhchem_output_additionCompound: }
                   { s }
                   \__mhchem_cf_loop:
               }{
             \peek_charcode:NTF +
               {
-                \str_if_eq:VnF \__mhchem_cf_supState_tl { - }
-                  { \__mhchem_cf_outputAndReset: }
-                \tl_set:Nn \__mhchem_cf_supState_tl { d }
-                \tl_set:Nn \__mhchem_cf_state_tl { e }
+                \tl_set:Nn \l__mhchem_cf_supState_tl { d }
+                \tl_set:Nn \l__mhchem_cf_state_tl { e }
                 \__mhchem_cf_loop:
               }{
-            \peek_charcode:NTF |
+            \__mhchem_regex_peek:nTF { [ \( \[ ] }
               {
-                \PackageWarning{mhchem}{The symbol | is not allowed here}
-                \__mhchem_loopHelper_ignoreNextToken:Nn \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF (
-              {
-                \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:NNn
-                  { s }
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF )
-              {
-                \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:NNn
-                  { a }
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF [
-              {
-                \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:NNn
+                \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:nNn
                   { s }
                   \__mhchem_cf_loop:
               }{
-            \peek_charcode:NTF ]
+            \__mhchem_regex_peek:nTF { [ \) \] \/ ] }
               {
-                \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:NNn
+                \__mhchem_loopHelper_outputAndReset_appendNextTokenToResult_setState:nNn
                   { a }
                   \__mhchem_cf_loop:
               }{
             \peek_catcode:NTF \mhchem@macro
               {
                 \__mhchem_cf_outputAndReset:
-                \tl_set:Nn \__mhchem_cf_state_tl { c }
+                \tl_set:Nn \l__mhchem_cf_state_tl { c }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_result_tl
+                  \l__mhchem_cf_element_tl
                   \__mhchem_cf_loop:
               }{
             \peek_catcode:NTF a  % letter
               {
-                \str_if_eq:VnF \__mhchem_cf_supState_tl { - }
-                  { \__mhchem_cf_outputAndReset: }
-                \str_if_eq:VnF \__mhchem_cf_subState_tl { - }
-                  { \__mhchem_cf_outputAndReset: }
+                \str_if_eq:VnTF \l__mhchem_cf_supState_tl { - }
+                  {
+                    \str_if_eq:VnF \l__mhchem_cf_subState_tl { - }
+                      { \__mhchem_cf_outputAndReset: }
+                  }
+                  {
+                    \regex_match:nVTF
+                      { \A [0-9]+ \Z}
+                      \l__mhchem_cf_sup_tl
+                      {
+                        \tl_set:NV \l__mhchem_cf_loop_tmpa_l \l__mhchem_cf_sup_tl
+                        \tl_set:NV \l__mhchem_cf_loop_tmpb_l \l__mhchem_cf_supState_tl
+                        \tl_set:NV \l__mhchem_cf_loop_tmpc_l \l__mhchem_cf_sub_tl
+                        \tl_set:NV \l__mhchem_cf_loop_tmpd_l \l__mhchem_cf_subState_tl
+                        \tl_clear:N \l__mhchem_cf_sup_tl
+                        \tl_set:Nn \l__mhchem_cf_supState_tl { - }
+                        \tl_clear:N \l__mhchem_cf_sub_tl
+                        \tl_set:Nn \l__mhchem_cf_subState_tl { - }
+                        \__mhchem_cf_outputAndReset:
+                        \tl_set:NV \l__mhchem_cf_presup_tl \l__mhchem_cf_loop_tmpa_l
+                        \tl_set:NV \l__mhchem_cf_presupState_tl \l__mhchem_cf_loop_tmpb_l
+                        \tl_set:NV \l__mhchem_cf_presub_tl \l__mhchem_cf_loop_tmpc_l
+                        \tl_set:NV \l__mhchem_cf_presubState_tl \l__mhchem_cf_loop_tmpd_l
+                      }
+                      { \__mhchem_cf_outputAndReset: }
+                  }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_element_tl
+                  \l__mhchem_cf_element_tl
                   \__mhchem_cf_loop:
               }{
-            \peek_catcode:NTF 1  % number
+            \__mhchem_regex_peek:nTF { [ 0-9 ] }
               {
-                \str_if_eq:VnF \__mhchem_cf_subState_tl { - }
+                \str_if_eq:VnF \l__mhchem_cf_subState_tl { - }
                   { \__mhchem_cf_outputAndReset: }
-                \tl_set:Nn \__mhchem_cf_subState_tl { d }
-                \tl_set:Nn \__mhchem_cf_state_tl { f }
+                \tl_set:Nn \l__mhchem_cf_subState_tl { d }
+                \tl_set:Nn \l__mhchem_cf_state_tl { f }
                 \__mhchem_cf_loop:
               }{
             \peek_catcode:NTF \c_group_begin_token
               {
                 \__mhchem_cf_outputAndReset:
-                \__mhchem_loopHelper_appendNextGroup:NNn
-                  \__mhchem_cf_result_tl
-                  \__mhchem_cf_loop:
+                \int_compare:nTF { \l__mhchem_option_version_int < 4 }
+                  {
+                    \__mhchem_loopHelper_appendNextGroup:NNn
+                      \l__mhchem_cf_result_tl
+                      \__mhchem_cf_loop:
+                  }
+                % else
+                  {
+                    \__mhchem_loopHelper_appendNextGroup_prefix_ifEmpty:NnnNn
+                      \l__mhchem_cf_element_tl
+                      { \__mhchem_cg_escapeFromMathToTextOrFaketext:n }
+                      {}
+                      \__mhchem_cf_loop:
+                  }
               }{
             \peek_catcode_remove:NTF \c_math_toggle_token
               {
-                \str_if_eq:VnF \__mhchem_cf_supState_tl { - }
+                \str_if_eq:VnF \l__mhchem_cf_supState_tl { - }
                   { \__mhchem_cf_outputAndReset: }
-                \str_if_eq:VnF \__mhchem_cf_subState_tl { - }
+                \str_if_eq:VnF \l__mhchem_cf_subState_tl { - }
                   { \__mhchem_cf_outputAndReset: }
-                \__mhchem_loopHelper_appendMathB:NNw
-                  \__mhchem_cf_element_tl
-                  \__mhchem_cf_loop:
+                \__mhchem_loopHelper_appendMathB:nn
+                  { l__mhchem_cf_element_tl }
+                  { __mhchem_cf_loop: }
               }
             % else
               {
                 \__mhchem_cf_outputAndReset:
-                \tl_set:Nn \__mhchem_cf_state_tl { s }
+                \tl_set:Nn \l__mhchem_cf_state_tl { s }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_result_tl
+                  \l__mhchem_cf_result_tl
                   \__mhchem_cf_loop:
               }
-            }}}}}}}}}}}}}}}}}}}
+            }}}}}}}}}}}}}}}
           }
         { e }
           {
-            \peek_charcode:NTF 1
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { e+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 2
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { e+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 3
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { e+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 4
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { e+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 5
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { e+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 6
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { e+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 7
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { e+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 8
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { e+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 9
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { e+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 0
+            \__mhchem_regex_peek:nTF { [0-9] }
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { e+ }
+                \tl_set:Nn \l__mhchem_cf_state_tl { e+ }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
+                  \l__mhchem_cf_sup_tl
                   \__mhchem_cf_loop:
               }{
             \peek_catcode_remove:NTF \c_math_toggle_token
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { a }
-                \__mhchem_loopHelper_appendMathAsGroup:NNw
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
+                \tl_set:Nn \l__mhchem_cf_state_tl { a }
+                \__mhchem_loopHelper_appendMathB:nn
+                  { l__mhchem_cf_sup_tl }
+                  { __mhchem_cf_loop: }
               }
             % else
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { a }
+                \tl_set:Nn \l__mhchem_cf_state_tl { a }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
+                  \l__mhchem_cf_sup_tl
                   \__mhchem_cf_loop:
               }
-            }}}}}}}}}}
+            }
           }
         { e+ }
           {
-            \peek_charcode:NTF 1
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 2
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 3
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 4
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 5
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 6
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 7
+            \__mhchem_regex_peek:nTF { [ 0-9 \+ ] }
               {
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 8
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 9
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 0
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF +
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
+                  \l__mhchem_cf_sup_tl
                   \__mhchem_cf_loop:
               }{
             \peek_charcode:NTF -
               {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sup_tl
-                  \__mhchem_cf_loop:
+                \regex_match:nVTF
+                  { \A (\c{eta}|\c{mu}|\c{kappa}) \Z }
+                  \l__mhchem_cf_element_tl
+                  {
+                    \tl_set:Nn \l__mhchem_cf_state_tl { - }
+                    \__mhchem_loopHelper_ignoreNextToken:Nn
+                      \__mhchem_cf_loop:
+                  }
+                  {
+                    \__mhchem_loopHelper_appendNextToken:NNn
+                      \l__mhchem_cf_sup_tl
+                      \__mhchem_cf_loop:
+                  }
               }
             % else
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { a }
+                \tl_set:Nn \l__mhchem_cf_state_tl { a }
                 \__mhchem_cf_loop:
               }
-            }}}}}}}}}}}
+            }
           }
         { f }
           {
-            \peek_charcode:NTF 1
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { f+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 2
+            \__mhchem_regex_peek:nTF { [0-9] }
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { f+ }
+                \tl_set:Nn \l__mhchem_cf_state_tl { f+ }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 3
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { f+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 4
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { f+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 5
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { f+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 6
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { f+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 7
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { f+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 8
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { f+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 9
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { f+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 0
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { f+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
+                  \l__mhchem_cf_sub_tl
                   \__mhchem_cf_loop:
               }{
             \peek_catcode_remove:NTF \c_math_toggle_token
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { a }
-                \__mhchem_loopHelper_appendMathAsGroup:NNw
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
+                \tl_set:Nn \l__mhchem_cf_state_tl { a }
+                \__mhchem_loopHelper_appendMathB:nn
+                  { l__mhchem_cf_sub_tl }
+                  { __mhchem_cf_loop: }
               }
             % else
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { a }
+                \tl_set:Nn \l__mhchem_cf_state_tl { a }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
+                  \l__mhchem_cf_sub_tl
                   \__mhchem_cf_loop:
               }
-            }}}}}}}}}}
+            }
           }
         { f+ }
           {
-            \peek_charcode:NTF 1
+            \__mhchem_regex_peek:nTF { [0-9] }
               {
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 2
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 3
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 4
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 5
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 6
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 7
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 8
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 9
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 0
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_sub_tl
+                  \l__mhchem_cf_sub_tl
                   \__mhchem_cf_loop:
               }
             % else
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { a }
+                \tl_set:Nn \l__mhchem_cf_state_tl { a }
                 \__mhchem_cf_loop:
               }
-            }}}}}}}}}
           }
         { p }
           {
-            \peek_charcode:NTF 1
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { p+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 2
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { p+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 3
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { p+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 4
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { p+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 5
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { p+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 6
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { p+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 7
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { p+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 8
+            \__mhchem_regex_peek:nTF { [0-9] }
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { p+ }
+                \tl_set:Nn \l__mhchem_cf_state_tl { p+ }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 9
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { p+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 0
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { p+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
+                  \l__mhchem_cf_presup_tl
                   \__mhchem_cf_loop:
               }{
             \peek_catcode_remove:NTF \c_math_toggle_token
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { s }
-                \__mhchem_loopHelper_appendMathAsGroup:NNw
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
+                \tl_set:Nn \l__mhchem_cf_state_tl { s }
+                \__mhchem_loopHelper_appendMathB:nn
+                  { l__mhchem_cf_presup_tl }
+                  { __mhchem_cf_loop: }
               }
             % else
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { s }
+                \tl_set:Nn \l__mhchem_cf_state_tl { s }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
+                  \l__mhchem_cf_presup_tl
                   \__mhchem_cf_loop:
-              }}}}}}}}}}}
+              }
+            }
           }
         { p+ }
           {
-            \peek_charcode:NTF 1
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 2
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 3
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 4
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 5
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 6
+            \__mhchem_regex_peek:nTF { [0-9] }
               {
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 7
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 8
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 9
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 0
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presup_tl
+                  \l__mhchem_cf_presup_tl
                   \__mhchem_cf_loop:
               }
             % else
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { s }
+                \tl_set:Nn \l__mhchem_cf_state_tl { s }
                 \__mhchem_cf_loop:
-              }}}}}}}}}}
+              }
           }
         { q }
           {
-            \peek_charcode:NTF 1
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { q+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 2
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { q+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 3
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { q+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 4
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { q+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 5
+            \__mhchem_regex_peek:nTF { [0-9] }
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { q+ }
+                \tl_set:Nn \l__mhchem_cf_state_tl { q+ }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 6
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { q+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 7
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { q+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 8
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { q+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 9
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { q+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 0
-              {
-                \tl_set:Nn \__mhchem_cf_state_tl { q+ }
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
+                  \l__mhchem_cf_presub_tl
                   \__mhchem_cf_loop:
               }{
             \peek_catcode_remove:NTF \c_math_toggle_token
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { s }
-                \__mhchem_loopHelper_appendMathAsGroup:NNw
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
+                \tl_set:Nn \l__mhchem_cf_state_tl { s }
+                \__mhchem_loopHelper_appendMathB:nn
+                  { l__mhchem_cf_presub_tl }
+                  { __mhchem_cf_loop: }
               }
             % else
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { s }
+                \tl_set:Nn \l__mhchem_cf_state_tl { s }
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
+                  \l__mhchem_cf_presub_tl
                   \__mhchem_cf_loop:
-              }}}}}}}}}}}
+              }
+            }
           }
         { q+ }
           {
-            \peek_charcode:NTF 1
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 2
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 3
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 4
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 5
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 6
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 7
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 8
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 9
-              {
-                \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
-                  \__mhchem_cf_loop:
-              }{
-            \peek_charcode:NTF 0
+            \__mhchem_regex_peek:nTF { [0-9] }
               {
                 \__mhchem_loopHelper_appendNextToken:NNn
-                  \__mhchem_cf_presub_tl
+                  \l__mhchem_cf_presub_tl
                   \__mhchem_cf_loop:
               }
             % else
               {
-                \tl_set:Nn \__mhchem_cf_state_tl { s }
+                \tl_set:Nn \l__mhchem_cf_state_tl { s }
                 \__mhchem_cf_loop:
-              }}}}}}}}}}
+              }
           }
       }
       {
         \msg_error:nnx { mhchem } { cf / unexpected-state }
-          { \__mhchem_cf_state_tl }
+          { \l__mhchem_cf_state_tl }
         \__mhchem_loopHelper_appendNextToken:NNn
-          \__mhchem_cf_result_tl
+          \l__mhchem_cf_result_tl
           \__mhchem_cf_loop:
       }
     }}}
   }
-\def\mhchem@cf@switchState#1#2|{%
-  \ifthenelse{\equal{1}{#2}}{%
-    \tl_set:Nn \__mhchem_cf_state_tl { a }%
-  }{%
-    \PackageWarning{mhchem}{Command |#2| unknown}%
-  }%
-  \mhchem@cf@continue%
-}%
 
 \cs_new_protected:Npn \__mhchem_cf_output:
   {
-    \str_if_eq:nnTF
+    \bool_if:nTF
       {
-        \__mhchem_cf_presup_tl
-        \__mhchem_cf_presub_tl
-        \__mhchem_cf_element_tl
-        \__mhchem_cf_supA_tl%todo remove
-        \__mhchem_cf_sub_tl
-        \__mhchem_cf_sup_tl
+        \tl_if_empty_p:N \l__mhchem_cf_presup_tl  &&
+        \tl_if_empty_p:N \l__mhchem_cf_presub_tl  &&
+        \tl_if_empty_p:N \l__mhchem_cf_element_tl  &&
+        \tl_if_empty_p:N \l__mhchem_cf_sub_tl  &&
+        \tl_if_empty_p:N \l__mhchem_cf_sup_tl
       }
-      {} % is empty?
       {
       }
       {
-        \str_case:Vnn \__mhchem_cf_state_tl
+        \tl_set:NV \l__mhchem_cf_lastElement_tl \l__mhchem_cf_element_tl
+        \str_case:Vnn \l__mhchem_cf_state_tl
           {
             { 1 }
               {
-                \tl_put_right:Nx \__mhchem_cf_result_tl
+                \__mhchem_cg_replaceForAmount:N \l__mhchem_cf_element_tl
+                \tl_put_right:Nx \l__mhchem_cf_result_tl
                   {
-                    \exp_not:N \mhchem@mathOrText {
-                    \exp_not:N \mhchem@cf@frac
-                    \exp_not:V \__mhchem_cf_element_tl / \exp_not:N \mhchem@END
-                    { \exp_not:N \mhchem@option@skipAfterAmount } }
+                    \exp_not:N \__mhchem_output_withFont:n {
+                    \exp_not:V \l__mhchem_cf_element_tl
+                    }
+                    \exp_not:N \mhchem@option@skipAfterAmount
                   }
               }
             { 9 }
               {
-                \tl_put_right:Nx \__mhchem_cf_result_tl
+                \__mhchem_cg_replaceForAmount:N \l__mhchem_cf_element_tl
+                \tl_put_right:Nx \l__mhchem_cf_result_tl
                   {
-                    \exp_not:N \mhchem@mathOrText {
-                    \exp_not:N \mhchem@cf@frac
-                    \exp_not:V \__mhchem_cf_element_tl /
-                    \exp_not:N \mhchem@END
-                    {} }
+                    \exp_not:N \__mhchem_output_withFont:n {
+                    \exp_not:V \l__mhchem_cf_element_tl
+                    }
                   }
               }
           }
           {
-            \str_if_eq:VnTF \__mhchem_cf_supState_tl { rm }
-              {
-                \tl_set:Nx \__mhchem_cf_sup_tl { \exp_not:N \ensuremath { \exp_not:N \mathrm { \exp_not:V \__mhchem_cf_sup_tl } } }
-              }
-              {}
-            \str_if_eq:VnT \__mhchem_cf_subState_tl { rm }
-              {
-                \tl_set:Nx \__mhchem_cf_sub_tl { \exp_not:N \ensuremath { \exp_not:N \mathrm { \exp_not:V \__mhchem_cf_sub_tl } } }
-              }
-            \str_if_eq:VnTF \__mhchem_cf_presupState_tl { rm }
-              {
-                \tl_set:Nx \__mhchem_cf_presup_tl { \exp_not:N \ensuremath { \exp_not:N \mathrm { \exp_not:V \__mhchem_cf_presup_tl } } }
-              }
-              {}
-            \str_if_eq:VnT \__mhchem_cf_presubState_tl { rm }
-              {
-                \tl_set:Nx \__mhchem_cf_presub_tl { \exp_not:N \ensuremath { \exp_not:N \mathrm { \exp_not:V \__mhchem_cf_presub_tl } } }
-              }
-            \str_case:Vnn \__mhchem_cf_supState_tl
+            \str_if_eq:VnTF \l__mhchem_cf_presupState_tl { rm }
+              { \tl_set:Nx \l__mhchem_cf_presup_tl { \exp_not:N \__mhchem_output_escapeToRomanMath:n { \exp_not:V \l__mhchem_cf_presup_tl } } }
+              { \__mhchem_cg_replaceForSuperscript:N \l__mhchem_cf_presup_tl }
+            \str_if_eq:VnTF \l__mhchem_cf_presubState_tl { rm }
+              { \tl_set:Nx \l__mhchem_cf_presub_tl { \exp_not:N \__mhchem_output_escapeToRomanMath:n { \exp_not:V \l__mhchem_cf_presub_tl } } }
+              { \__mhchem_cg_replaceForSubscript:N \l__mhchem_cf_presub_tl }
+            \__mhchem_cg_replaceForElement:N \l__mhchem_cf_element_tl
+            \str_if_eq:VnTF \l__mhchem_cf_subState_tl { rm }
+              { \tl_set:Nx \l__mhchem_cf_sub_tl { \exp_not:N \__mhchem_output_escapeToRomanMath:n { \exp_not:V \l__mhchem_cf_sub_tl } } }
+              { \__mhchem_cg_replaceForSubscript:N \l__mhchem_cf_sub_tl }
+            \str_if_eq:VnTF \l__mhchem_cf_supState_tl { rm }
+              { \tl_set:Nx \l__mhchem_cf_sup_tl { \exp_not:N \__mhchem_output_escapeToRomanMath:n { \exp_not:V \l__mhchem_cf_sup_tl } } }
+              { \__mhchem_cg_replaceForSuperscript:N \l__mhchem_cf_sup_tl }
+            \bool_if:nT
+              {
+                \str_if_eq_p:Vn \l__mhchem_cf_supState_tl { kv }  &&
+                \str_if_eq_p:Vn \l__mhchem_cf_sub_tl {}
+              }
+              { \tl_set:Nn \l__mhchem_cf_supState_tl { d } }
+            \str_case:Vnn \l__mhchem_cf_supState_tl
               {
                 { kv }
                   {
-                    \tl_put_right:Nx \__mhchem_cf_result_tl
+                    \tl_put_right:Nx \l__mhchem_cf_result_tl
                       {
-                        \exp_not:N \__mhchem_chemfive:nnnnnn
-                          {
-                            \exp_not:N \__mhchem_cf_replaceMath:n
-                              { \exp_not:V \__mhchem_cf_presup_tl }
-                          }
-                          {
-                            \exp_not:N \__mhchem_cf_replaceMath:n
-                              { \exp_not:V \__mhchem_cf_presub_tl }
-                          }
-                          { \exp_not:V \__mhchem_cf_element_tl }
-                          {
-                            \exp_not:N \__mhchem_cf_replaceMathMinusDot:n
-                              { \exp_not:V \__mhchem_cf_sup_tl }
-                          }
-                          {
-                            \exp_not:N \__mhchem_cf_replaceMath:n
-                              { \exp_not:V \__mhchem_cf_sub_tl }
-                          }
+                        \exp_not:N \__mhchem_output_coreFive:nnnnnn
+                          { \exp_not:V \l__mhchem_cf_presup_tl }
+                          { \exp_not:V \l__mhchem_cf_presub_tl }
+                          { \exp_not:V \l__mhchem_cf_element_tl }
+                          { \exp_not:V \l__mhchem_cf_sup_tl }
+                          { \exp_not:V \l__mhchem_cf_sub_tl }
                           {}
                      }
                   }
               }
               {
-                \tl_put_right:Nx \__mhchem_cf_result_tl
+                \tl_put_right:Nx \l__mhchem_cf_result_tl
                   {
-                    \exp_not:N \__mhchem_chemfive:nnnnnn
-                      {
-                        \exp_not:N \__mhchem_cf_replaceMath:n
-                          { \exp_not:V \__mhchem_cf_presup_tl }
-                      }
-                      {
-                        \exp_not:N \__mhchem_cf_replaceMath:n
-                          { \exp_not:V \__mhchem_cf_presub_tl }
-                      }
-                      { \exp_not:V \__mhchem_cf_element_tl }
+                    \exp_not:N \__mhchem_output_coreFive:nnnnnn
+                      { \exp_not:V \l__mhchem_cf_presup_tl }
+                      { \exp_not:V \l__mhchem_cf_presub_tl }
+                      { \exp_not:V \l__mhchem_cf_element_tl }
                       {}
-                      {
-                        \exp_not:N \__mhchem_cf_replaceMath:n
-                          { \exp_not:V \__mhchem_cf_sub_tl }
-                      }
-                      {
-                        \exp_not:N \__mhchem_cf_replaceMathMinusDot:n
-                          { \exp_not:V \__mhchem_cf_sup_tl }
-                      }
-                   }
+                      { \exp_not:V \l__mhchem_cf_sub_tl }
+                      { \exp_not:V \l__mhchem_cf_sup_tl }
+                  }
               }
           }
       }
   }
+\cs_new_protected:Npn \__mhchem_cf_outputRawElement:
+  {
+    \tl_set:NV \l__mhchem_cf_lastElement_tl \l__mhchem_cf_element_tl
+    \tl_put_right:Nx \l__mhchem_cf_result_tl  { \exp_not:V \l__mhchem_cf_element_tl }
+  }
 \cs_new_protected:Npn \__mhchem_cf_outputAndReset:
   {
     \__mhchem_cf_output:
     \__mhchem_cf_resetOutput:
   }
+\cs_new_protected:Npn \__mhchem_cf_outputRawElementAndReset:
+  {
+    \__mhchem_cf_outputRawElement:
+    \__mhchem_cf_resetOutput:
+  }
+\cs_new_protected:Npn \__mhchem_cf_outputRawElementAndReset:n #1
+  {
+    \tl_put_right:Nn \l__mhchem_cf_element_tl {#1}
+    \__mhchem_cf_outputRawElementAndReset:
+  }
 
-%%% frac
-\def\mhchem@cf@frac#1/#2\mhchem@END#3{%
-  \ifthenelse{\equal{#2}{}}{%
-    #1#3%
-  }{%
-    \ensuremath{\mathchoice%
-      {\textstyle%
-       \frac{\mhchem@mathOrText{#1}}{\mhchem@mathOrText{\mhchem@getfirstchar#2\mhchem@ENDgetfirstchar}}#3}%
-      {\frac{\mhchem@mathOrText{#1}}{\mhchem@mathOrText{\mhchem@getfirstchar#2\mhchem@ENDgetfirstchar}}#3}%
-      {\frac{\mhchem@mathOrText{#1}}{\mhchem@mathOrText{\mhchem@getfirstchar#2\mhchem@ENDgetfirstchar}}#3}%
-      {\frac{\mhchem@mathOrText{#1}}{\mhchem@mathOrText{\mhchem@getfirstchar#2\mhchem@ENDgetfirstchar}}#3}%
-    }%
-  }%
-}%
-\def\mhchem@getfirstchar#1#2\mhchem@ENDgetfirstchar{#1}
-\def\mhchem@getlastchars#1#2\mhchem@ENDgetlastchars{#2}
-
-%%% replaceMath
-\tl_new:N \__mhchem_cf_replaceMath_result_tl
-\cs_new_protected:Npn \__mhchem_cf_replaceMath:n #1
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%   cg   %%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\cs_new_protected:Npn \__mhchem_cg_withinMathTokens:n #1
   {
-    \tl_clear:N \__mhchem_cf_replaceMath_result_tl
-    \__mhchem_cf_replaceMath_loop: #1 \q_recursion_stop
-    \__mhchem_cf_replaceMath_result_tl
+    \int_compare:nTF { \l__mhchem_option_version_int > 3 }
+      {
+        \regex_match:nnTF
+          { \A \cB. [^\cE.]* \cE. \Z } {#1}
+          {
+            \__mhchem_output_escapeFromMathToItalicMath:n { #1 }
+          }
+        % else
+          {
+            \regex_match:nnTF
+              { \A [1-9a-zA-Z\ \~\+\-\,\.\(\)\c{alpha}\c{beta}\c{gamma}\c{delta}\c{epsilon}\c{zeta}\c{eta}\c{theta}\c{iota}\c{kappa}\c{lambda}\c{mu}\c{nu}\c{xi}\c{omicron}\c{pi}\c{rho}\c{sigma}\c{tau}\c{upsilon}\c{phi}\c{chi}\c{psi}\c{omega}\c{Alpha}\c{Beta}\c{Gamma}\c{Delta}\c{Epsilon}\c{Zeta}\c{Eta}\c{Theta}\c{Iota}\c{Kappa}\c{Lambda}\c{Mu}\c{Nu}\c{Xi}\c{Omicron}\c{Pi}\c{Rho}\c{Sigma}\c{Tau}\c{Upsilon}\c{Phi}\c{Chi}\c{Psi}\c{Omega}]+ \Z }
+              {#1}
+              {
+                  {
+                    \bool_if:NTF \l__mhchem_output_isMathMode_bool
+                      {
+                        \int_compare:nT
+                          { \l__mhchem_option_version_int > 3 }
+                          {
+                            \thinmuskip=0mu
+                            \medmuskip=0mu
+                            \thickmuskip=0mu
+                          }
+                        \__mhchem_output_escapeFromMathToItalicMath:n {#1}
+                      }
+                      {
+                        \tl_set:Nn \l_tmpa_tl { #1 }
+                        \regex_replace_all:nnN
+                          { [a-zA-Z]+ }
+                          { \c{__mhchem_output_escapeFromTextToItalicText:n} \cB[ \0 \cE] }
+                          \l_tmpa_tl
+                        \regex_replace_all:nnN
+                          { [\ ]+ }
+                          {}
+                          \l_tmpa_tl
+                        \regex_replace_all:nnN
+                          { - }
+                          { \c{mhchem@option@textminus} }
+                          \l_tmpa_tl
+                        \tl_use:N \l_tmpa_tl
+                      }
+                  }
+              }
+              {
+                \bool_if:NTF \l__mhchem_output_isMathMode_bool
+                  { \__mhchem_output_escapeFromMathToItalicMath:n {#1} }
+                  { \__mhchem_output_escapeFromTextToItalicMath:n {#1} }
+              }
+          }
+      }
+    % else
+      {
+        \__mhchem_output_escapeFromMathToItalicMath:n {#1}
+      }
   }
-\cs_new_protected:Npn \__mhchem_cf_replaceMath_loop:
+\cs_new_protected:Npn \__mhchem_cg_itshape:n #1
+  {
+    \int_compare:nTF { \l__mhchem_option_version_int > 3 }
+      {
+        \bool_if:NTF \l__mhchem_output_isMathMode_bool
+          { \__mhchem_output_escapeFromMathToItalicMath:n {#1} }
+          { \__mhchem_output_escapeFromTextToItalicText:n {#1} }
+      }
+      { #1 }
+  }
+\cs_new_protected:Npn \__mhchem_cg_escapeFromMathToTextOrFaketext:n #1
+  {
+    \bool_if:NTF \l__mhchem_output_isMathMode_bool
+      { \__mhchem_cg_escapeFromMathToFakeText:n {#1} }
+      { \__mhchem_output_escapeFromMathToText:n { #1 } }
+  }
+\tl_new:N \l__mhchem_cg_escapeFromMathToFakeText_result_tl
+\cs_new_protected:Npn \__mhchem_cg_escapeFromMathToFakeText:n #1
+  {
+    \tl_clear:N \l__mhchem_cg_escapeFromMathToFakeText_result_tl
+    \__mhchem_cg_escapeFromMathToFakeText_loop: #1 \q_recursion_stop
+    \__mhchem_output_escapeFromMathToRomanMath:n { \tl_use:N \l__mhchem_cg_escapeFromMathToFakeText_result_tl }
+  }
+\cs_new_protected:Npn \__mhchem_cg_escapeFromMathToFakeText_loop:
   {
     \peek_meaning:NTF \q_recursion_stop
       { \use_none:n }
       {
-    \peek_catcode_remove:NTF \c_math_toggle_token % math $
+    \peek_charcode_remove:NTF \c_space_token
+      {
+        \tl_put_right:Nn
+          \l__mhchem_cg_escapeFromMathToFakeText_result_tl
+          { \mkern6mu }
+        \__mhchem_cg_escapeFromMathToFakeText_loop:
+      }{
+    \peek_charcode_remove:NTF -
+      {
+        \tl_put_right:Nn
+          \l__mhchem_cg_escapeFromMathToFakeText_result_tl
+          { \mhchem@hyphen }
+        \__mhchem_cg_escapeFromMathToFakeText_loop:
+      }{
+    \peek_catcode_remove:NTF \c_math_toggle_token
       {
-        \__mhchem_loopHelper_appendMathB:NNw
-          \__mhchem_cf_replaceMath_result_tl
-          \__mhchem_cf_replaceMath_loop:
+        \__mhchem_loopHelper_appendMathB:nn
+          { l__mhchem_cg_escapeFromMathToFakeText_result_tl }
+          { __mhchem_cg_escapeFromMathToFakeText_loop: }
       }
       {
     \peek_catcode:NTF \c_group_begin_token
       {
         \__mhchem_loopHelper_appendNextGroup:NNn
-          \__mhchem_cf_replaceMath_result_tl
-          \__mhchem_cf_replaceMath_loop:
+          \l__mhchem_cg_escapeFromMathToFakeText_result_tl
+          \__mhchem_cg_escapeFromMathToFakeText_loop:
       }
     % else
       {
         \__mhchem_loopHelper_appendNextToken:NNn
-          \__mhchem_cf_replaceMath_result_tl
-          \__mhchem_cf_replaceMath_loop:
+          \l__mhchem_cg_escapeFromMathToFakeText_result_tl
+          \__mhchem_cg_escapeFromMathToFakeText_loop:
       }
-    }}
+    }}}}
+  }
+
+\cs_new_protected:Npn \__mhchem_cg_replaceForAmount:N #1
+  {
+    \regex_replace_once:nnN
+      { \A ([0-9]+)\/([0-9]+) \Z } { \c{__mhchem_cg_frac:nn} \cB[\1\cE] \cB[\2\cE] } #1
   }
-%%% replaceMathMinusDot
-\tl_new:N \__mhchem_cf_replaceMathMinusDot_result_tl
-\cs_new_protected:Npn \__mhchem_cf_replaceMathMinusDot:n #1
+\cs_new_protected:Npn \__mhchem_cg_frac:nn #1#2
   {
-    \tl_clear:N \__mhchem_cf_replaceMathMinusDot_result_tl
-    \__mhchem_cf_replaceMathMinusDot_loop: #1 \q_recursion_stop
-    \__mhchem_cf_replaceMathMinusDot_result_tl
+    \ensuremath{\frac
+      { \__mhchem_output_withFont:n {#1} }
+      { \__mhchem_output_withFont:n {#2} }
+    }
+  }
+
+\cs_new_protected:Npn \__mhchem_cg_replaceForElement:N #1
+  {}
+
+\tl_new:N \l__mhchem_cg_replaceForSubscript_result_tl
+\tl_new:N \l__mhchem_cg_replaceForSubscript_state_tl
+\cs_new_protected:Npn \__mhchem_cg_replaceForSubscript:N #1
+  {
+    \int_compare:nTF { \l__mhchem_option_version_int > 3}
+      {
+        \regex_match:nVTF
+          { \A( [nmpx] | ([0-9\ \+\-\,\.\(\)]+ [nmpx] [0-9\ \+\-\,\.\(\)]*)+ | ([0-9\ \+\-\,\.\(\)]* [nmpx] [0-9\ \+\-\,\.\(\)]+)+ )\Z }
+          #1
+          {
+            \regex_replace_all:nnN
+              { [nmpx] }
+              { \c{__mhchem_output_withFont:n}\cB[ \c{__mhchem_cg_itshape:n}\cB[ \0 \cE]\cE] }
+              #1
+            \regex_replace_all:nnN
+              { - }
+              { \c{__mhchem_output_minus:} }
+              #1
+            \regex_replace_all:nnN
+              { \d\,\d }
+              { \c{__mhchem_output_commaDecimal:} }
+              #1
+          }
+          {
+            \tl_clear:N \l__mhchem_cg_replaceForSubscript_result_tl
+            \tl_set:Nn \l__mhchem_cg_replaceForSubscript_state_tl { s }
+            \exp_after:wN \__mhchem_cg_replaceForSubscript_loop: #1 \q_recursion_stop
+            \tl_set:NV #1 \l__mhchem_cg_replaceForSubscript_result_tl
+          }
+      }
+    % else
+      {
+        \tl_clear:N \l__mhchem_cg_replaceForSubscript_result_tl
+        \tl_set:Nn \l__mhchem_cg_replaceForSubscript_state_tl { s }
+        \exp_after:wN \__mhchem_cg_replaceForSubscript_loop: #1 \q_recursion_stop
+        \tl_set:NV #1 \l__mhchem_cg_replaceForSubscript_result_tl
+      }
   }
-\cs_new_protected:Npn \__mhchem_cf_replaceMathMinusDot_loop:
+\cs_new_protected:Npn \__mhchem_cg_replaceForSubscript_loop:
   {
     \peek_meaning:NTF \q_recursion_stop
       { \use_none:n }
       {
+    \__mhchem_regex_peek:nTF { [0-9] }
+      {
+        \tl_set:Nn \l__mhchem_cg_replaceForSubscript_state_tl { 9 }
+        \__mhchem_loopHelper_appendNextToken:NNn
+          \l__mhchem_cg_replaceForSubscript_result_tl
+          \__mhchem_cg_replaceForSubscript_loop:
+      }{
     \peek_charcode_remove:NTF -
       {
-        \tl_put_right:Nn \__mhchem_cf_replaceMathMinusDot_result_tl
-          { \mhchem@mathOrText@ii{-}{\mhchem@option@textminus} }
-        \__mhchem_cf_replaceMathMinusDot_loop:
+        \int_compare:nTF { \l__mhchem_option_version_int > 3 }
+          {
+            \tl_put_right:Nn \l__mhchem_cg_replaceForSubscript_result_tl
+              { \__mhchem_output_minus: }
+          }
+          {
+            \tl_put_right:Nn \l__mhchem_cg_replaceForSubscript_result_tl { - }
+          }
+          \tl_set:Nn \l__mhchem_cg_replaceForSubscript_state_tl { s }
+          \__mhchem_cg_replaceForSubscript_loop:
       }{
-    \peek_charcode_remove:NTF .
+    \peek_charcode_remove:NTF ,
       {
-        \tl_put_right:Nn \__mhchem_cf_replaceMathMinusDot_result_tl
-          { \ensuremath{\textbf{\fontfamily{cmr}\selectfont\textperiodcentered}} }
-        \__mhchem_cf_replaceMathMinusDot_loop:
+        \str_if_eq:VnTF \l__mhchem_cg_replaceForSubscript_state_tl { 9 }
+          {
+            \tl_put_right:Nn \l__mhchem_cg_replaceForSubscript_result_tl
+              { \__mhchem_output_commaAutoSmall: }
+          }
+          {
+            \tl_put_right:Nn \l__mhchem_cg_replaceForSubscript_result_tl
+              { \__mhchem_output_commaEnumerationSmall: }
+          }
+        \tl_set:Nn \l__mhchem_cg_replaceForSubscript_state_tl { s }
+        \__mhchem_cg_replaceForSubscript_loop:
       }{
-    \peek_catcode_remove:NTF \c_math_toggle_token % math $
+    \peek_catcode_remove:NTF \c_math_toggle_token
       {
-        \__mhchem_loopHelper_appendMathB:NNw
-          \__mhchem_cf_replaceMathMinusDot_result_tl
-          \__mhchem_cf_replaceMathMinusDot_loop:
+        \tl_set:Nn \l__mhchem_cg_replaceForSubscript_state_tl { s }
+        \__mhchem_loopHelper_appendMathB:nn
+          { l__mhchem_cg_replaceForSubscript_result_tl }
+          { __mhchem_cg_replaceForSubscript_loop: }
       }
       {
     \peek_catcode:NTF \c_group_begin_token
       {
+        \tl_set:Nn \l__mhchem_cg_replaceForSubscript_state_tl { s }
         \__mhchem_loopHelper_appendNextGroup:NNn
-          \__mhchem_cf_replaceMathMinusDot_result_tl
-          \__mhchem_cf_replaceMathMinusDot_loop:
+          \l__mhchem_cg_replaceForSubscript_result_tl
+          \__mhchem_cg_replaceForSubscript_loop:
       }
     % else
       {
+        \tl_set:Nn \l__mhchem_cg_replaceForSubscript_state_tl { s }
         \__mhchem_loopHelper_appendNextToken:NNn
-          \__mhchem_cf_replaceMathMinusDot_result_tl
-          \__mhchem_cf_replaceMathMinusDot_loop:
+          \l__mhchem_cg_replaceForSubscript_result_tl
+          \__mhchem_cg_replaceForSubscript_loop:
       }
-    }}}}
+    }}}}}
   }
 
-\cs_new_protected:Npn \__mhchem_defMathOrText:
+\tl_new:N \l__mhchem_cg_replaceForSuperscript_result_tl
+\tl_new:N \l__mhchem_cg_replaceForSuperscript_state_tl
+\cs_new_protected:Npn \__mhchem_cg_replaceForSuperscript:N #1
   {
-    \mode_if_math:TF
+    \tl_clear:N \l__mhchem_cg_replaceForSuperscript_result_tl
+    \tl_set:Nn \l__mhchem_cg_replaceForSuperscript_state_tl { s }
+    \exp_after:wN \__mhchem_cg_replaceForSuperscript_loop: #1 \q_recursion_stop
+    \tl_set:NV #1 \l__mhchem_cg_replaceForSuperscript_result_tl
+  }
+\cs_new_protected:Npn \__mhchem_cg_replaceForSuperscript_loop:
+  {
+    \peek_meaning:NTF \q_recursion_stop
       {
-        \int_compare:nTF { \__mhchem_option_version_int > 1 }
+        \str_if_eq:VnT \l__mhchem_cg_replaceForSuperscript_state_tl { 9. }
           {
-            \cs_set:Npx \mhchem@mathOrText ##1
-              {
-                \mode_if_math:TF
-                  { \exp_not:N \mhchem@option@mathFont{##1} }
-                  { \exp_not:N \text{##1} }
-              }
-            \cs_set:Npx \mhchem@mathOrText@ii ##1##2
+            \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+              { \__mhchem_output_electronDot: }
+          }
+        \use_none:n
+      }{
+    \peek_charcode_remove:NTF -
+      {
+        \str_if_eq:VnT \l__mhchem_cg_replaceForSuperscript_state_tl { 9. }
+          {
+            \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+              { \__mhchem_output_electronDot: }
+          }
+        \tl_set:Nn \l__mhchem_cg_replaceForSuperscript_state_tl { s }
+        \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+          { \__mhchem_output_minus: }
+        \__mhchem_cg_replaceForSuperscript_loop:
+      }{
+    \peek_charcode_remove:NTF .
+      {
+        \str_case:Vnn \l__mhchem_cg_replaceForSuperscript_state_tl
+          {
+            { 9. }
               {
-                \mode_if_math:TF
-                  { \exp_not:N \mhchem@option@mathFont{##1} }
-                  { ##2 }
+                \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+                  { \__mhchem_output_electronDot: \__mhchem_output_electronDot: }
+                \tl_set:Nn \l__mhchem_cg_replaceForSuperscript_state_tl { s }
               }
+            { 9 }
+              { \tl_set:Nn \l__mhchem_cg_replaceForSuperscript_state_tl { 9. } }
           }
-        % else
           {
-            \cs_set:Npx \mhchem@mathOrText ##1
+            \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+              { \__mhchem_output_electronDot: }
+          }
+        \__mhchem_cg_replaceForSuperscript_loop:
+      }{
+    \__mhchem_regex_peek:nTF { [ nmpx ] }
+      {
+        \str_if_eq:VnT \l__mhchem_cg_replaceForSuperscript_state_tl { 9. }
+          {
+            \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+              { \__mhchem_output_electronDot: }
+          }
+        \tl_set:Nn \l__mhchem_cg_replaceForSuperscript_state_tl { s }
+        \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+          { \__mhchem_cg_itshape:n }
+        \__mhchem_loopHelper_appendNextGroup:NNn
+          \l__mhchem_cg_replaceForSuperscript_result_tl
+          \__mhchem_cg_replaceForSuperscript_loop:
+      }{
+    \__mhchem_regex_peek:nTF { [0-9] }
+      {
+        \str_if_eq:VnT \l__mhchem_cg_replaceForSuperscript_state_tl { 9. }
+          { \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl { . } }
+        \tl_set:Nn \l__mhchem_cg_replaceForSuperscript_state_tl { 9 }
+        \__mhchem_loopHelper_appendNextToken:NNn
+          \l__mhchem_cg_replaceForSuperscript_result_tl
+          \__mhchem_cg_replaceForSuperscript_loop:
+      }{
+    \peek_charcode_remove:NTF *
+      {
+        \str_if_eq:VnT \l__mhchem_cg_replaceForSuperscript_state_tl { 9. }
+          {
+            \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+              { \__mhchem_output_electronDot: }
+          }
+        \tl_set:Nn \l__mhchem_cg_replaceForSuperscript_state_tl { s }
+        \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+          { \__mhchem_output_excited: }
+        \__mhchem_cg_replaceForSuperscript_loop:
+      }{
+    \peek_charcode_remove:NTF ,
+      {
+        \str_case:Vnn \l__mhchem_cg_replaceForSuperscript_state_tl
+          {
+            { 9. }
               {
-                \mode_if_math:TF { ##1 } { \exp_not:N \text{##1} }
+                \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+                  { \__mhchem_output_electronDot: }
               }
-            \cs_set:Npx \mhchem@mathOrText@ii ##1##2
+            { 9 }
               {
-                \mode_if_math:TF { ##1 } { ##2 }
-              }
+                \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+                  { \__mhchem_output_commaAutoSmall: }
+             }
+          }
+          {
+            \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+              { \__mhchem_output_commaEnumerationSmall: }
+          }
+          \tl_set:Nn \l__mhchem_cg_replaceForSuperscript_state_tl { s }
+          \__mhchem_cg_replaceForSuperscript_loop:
+      }{
+    \peek_catcode_remove:NTF \c_math_toggle_token
+      {
+        \str_if_eq:VnT \l__mhchem_cg_replaceForSuperscript_state_tl { 9. }
+          {
+            \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+              { \__mhchem_output_electronDot: }
+          }
+        \tl_set:Nn \l__mhchem_cg_replaceForSuperscript_state_tl { s }
+        \__mhchem_loopHelper_appendMathB:nn
+          { l__mhchem_cg_replaceForSuperscript_result_tl }
+          { __mhchem_cg_replaceForSuperscript_loop: }
+      }{
+    \peek_catcode:NTF \c_group_begin_token
+      {
+        \str_if_eq:VnT \l__mhchem_cg_replaceForSuperscript_state_tl { 9. }
+          {
+            \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+              { \__mhchem_output_electronDot: }
           }
+        \tl_set:Nn \l__mhchem_cg_replaceForSuperscript_state_tl { s }
+        \__mhchem_loopHelper_appendNextGroup:NNn
+          \l__mhchem_cg_replaceForSuperscript_result_tl
+          \__mhchem_cg_replaceForSuperscript_loop:
       }
     % else
       {
-
-        \mhchem@option@textFont
-        \cs_set:Npx \mhchem@mathOrText ##1 { \exp_not:N \text{##1} }
-        \cs_set:Npx \mhchem@mathOrText@ii ##1##2 { ##2 }
+        \str_if_eq:VnT \l__mhchem_cg_replaceForSuperscript_state_tl { 9. }
+          {
+            \tl_put_right:Nn \l__mhchem_cg_replaceForSuperscript_result_tl
+              { \__mhchem_output_electronDot: }
+          }
+        \tl_set:Nn \l__mhchem_cg_replaceForSuperscript_state_tl { s }
+        \__mhchem_loopHelper_appendNextToken:NNn
+          \l__mhchem_cg_replaceForSuperscript_result_tl
+          \__mhchem_cg_replaceForSuperscript_loop:
       }
+    }}}}}}}}
   }
-%%%%%%%%%%%%%%%%%%%%%
-%%%   @chemfive   %%%
-%%%%%%%%%%%%%%%%%%%%%
-\cs_new_protected:Npn \__mhchem_chemfive:nnnnnn #1#2#3#4#5#6
-  {
-    \bool_if:NTF \__mhchem_option_superscriptsStacked_bool
-      {
-        \__mhchem_prepostscript:nnnnnnnnn%
-          {\mhchem@mathOrText{2+}}%
-          {\mhchem@mathOrText{2}}%
-          {\mhchem@mathOrText{X}}%
-          {\mhchem@mathOrText{#1}}%
-          {\mhchem@mathOrText{#2}}%
-          {\mhchem@mathOrText@ii{\mhchem@option@mathFont{#3}}{\text{#3}}}%
-          {\mhchem@mathOrText{#4#6}}%
-          {\mhchem@mathOrText{#5}}%
-          {}%
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%   output   %%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\bool_new:N \l__mhchem_output_isMathMode_bool
+\cs_new_protected:Npn \__mhchem_output_defMathOrText:
+  {
+    \bool_if:nTF
+      {
+        \mode_if_math_p: ||
+        ( \l__mhchem_ce_ceActive_bool && \int_compare_p:n { \l__mhchem_option_version_int < 2 } )
+      }
+      {
+        \bool_set_true:N \l__mhchem_output_isMathMode_bool
       }
       {
-        \__mhchem_prepostscript:nnnnnnnnn%
-          {\mhchem@mathOrText{2+}}%
-          {\mhchem@mathOrText{2}}%
-          {\mhchem@mathOrText{X}}%
-          {\mhchem@mathOrText{#1}}%
-          {\mhchem@mathOrText{#2}}%
-          {\mhchem@mathOrText@ii{\mhchem@option@mathFont{#3}}{\text{#3}}}%
-          {\mhchem@mathOrText{#4}}%
-          {\mhchem@mathOrText{#5}}%
-          {\mhchem@mathOrText{#6}}%
+        \bool_set_false:N \l__mhchem_output_isMathMode_bool
+        \mhchem@option@textFont
       }
   }
-
-%%% @prepostscript
-\newlength\__mhchem_prepostscript_leftwidth%
-\newlength\__mhchem_prepostscript_leftwidth_ii%
-\cs_new_protected:Npn \__mhchem_prepostscript:nnnnnnnnn #1#2#3#4#5#6#7#8#9
+\cs_new_protected:Npn \__mhchem_output_coreFive:nnnnnn #1#2#3#4#5#6
   {
+    \group_begin:
+    \bool_if:nT
+      { \str_if_eq_p:nn {#6} {}  &&  ! \str_if_eq_p:nn {#4} {} }
+      { \bool_set_true:N \l__mhchem_option_superscriptsStacked_bool }
     \m@th
     \ensuremath
       {
-        \hbox_set:Nn \l_tmpa_box { $#4#5$ }
-        \dim_compare:nNnT { \box_wd:N \l_tmpa_box } > { 0pt }
+        \str_if_eq:nnF {#1#2} {}
           {
-            \hphantom { {}^{#4}\c_math_subscript_token{#5} }
-            { \vphantom {#3#6} }
+            \hphantom { {}^{\__mhchem_output_withFont:n{#1}}\c_math_subscript_token{\__mhchem_output_withFont:n{#2}} }
+            { \vphantom { \__mhchem_output_withFont:n { X } } }
             ^ {
                 \mhchem@mathboxrightt
                   {
-                    \vphantom {#1}
-                    #4
+                    \vphantom { \__mhchem_output_scriptWithFont:n { 2+ } }
+                    \__mhchem_output_scriptWithFont:n {#1}
                   }
               }
-            \c_math_subscript_token {
-                \mhchem@mathboxrightt
-                  {
-                    \vphantom {#2}
-                    #5
-                  }
+            \str_if_eq:nnF {#2} {}
+              {
+                \c_math_subscript_token {
+                  \mhchem@mathboxrightt
+                    {
+                      \smash{\__mhchem_output_scriptWithFont:n {#2}}
+                    }
+                }
               }
-            \mhchem@minispace %
+            \mhchem@minispace
           }
-        #6
-        \hbox_set:Nn \l_tmpa_box { $#7#8#9$ }
-        \dim_compare:nNnT { \box_wd:N \l_tmpa_box } > { 0pt }
+        \__mhchem_output_withFont:n {#3}
+        \str_if_eq:nnF {#4#6#5} {}
           {
-            \hbox_set:Nn \l_tmpa_box { $#6$ }
-            \dim_compare:nNnTF { \box_wd:N \l_tmpa_box } > { 0pt }
-              { { \vphantom {#3#6} } }
-              { \mhchem@minibackspace { \vphantom {#3} } }
-            \hbox_set:Nn \l_tmpa_box { $#8$ }
-            \dim_compare:nNnT { \box_wd:N \l_tmpa_box } > { 0pt }
+            \bool_if:NTF \l__mhchem_option_superscriptsStacked_bool
               {
-                \c_math_subscript_token {
-                    \vphantom { \smash[b]{#2} }
-                    #8
+                { \vphantom { \__mhchem_output_withFont:n { X } } }
+                \str_if_eq:nnF {#5} {}
+                  {
+                    \c_math_subscript_token
+                      {
+                        \vphantom { \__mhchem_output_scriptWithFont:n { 2 } }
+                        \smash[t] { \__mhchem_output_scriptWithFont:n {#5} }
+                      }
                   }
-              }
-            \hbox_set:Nn \l_tmpa_box { $#9$ }
-            \dim_compare:nNnTF { \box_wd:N \l_tmpa_box } = { 0pt }
-              {
                 ^ {
-                    \vphantom { \smash[t]{#1} }
-                    #7
+                    \vphantom { \smash[t] { \__mhchem_output_scriptWithFont:n { 2+ } } }
+                    \__mhchem_output_scriptWithFont:n {#4#6}
                   }
               }
+            % else
               {
-                ^ {
-                    \vphantom { \smash[t]{#1} }
-                    \hphantom {#8}
-                    #9
+                \bool_if:NTF \l__mhchem_option_subscriptsDeep_bool
+                  {
+                    { \vphantom { \__mhchem_output_withFont:n { X } } }
+                    \str_if_eq:nnF {#5} {}
+                      {
+                        \c_math_subscript_token
+                          {
+                            \vphantom { \__mhchem_output_scriptWithFont:n { 2 } }
+                            \smash[t] { \__mhchem_output_scriptWithFont:n {#5} }
+                          }
+                      }
+                    \str_if_eq:nnTF {#4#6} {}
+                      {
+                        ^ {
+                            \vphantom { \smash[t] { \__mhchem_output_scriptWithFont:n { 2+ } } }
+                          }
+                      }
+                      {
+                        ^ {
+                            \vphantom { \smash[t] { \__mhchem_output_scriptWithFont:n { 2+ } } }
+                            \hphantom { \__mhchem_output_scriptWithFont:n {#5} }
+                            \__mhchem_output_scriptWithFont:n {#4#6}
+                          }
+                      }
+                  }
+                  {
+                    \str_if_eq:nnF {#5} {}
+                      {
+                        { \vphantom { \__mhchem_output_withFont:n { X } } }
+                        \c_math_subscript_token
+                          {
+                            \vphantom { \__mhchem_output_scriptWithFont:n { 2 } }
+                            \smash[t] { \__mhchem_output_scriptWithFont:n {#5} }
+                          }
+                      }
+                    \str_if_eq:nnF {#4#6} {}
+                      {
+                        { \vphantom { \__mhchem_output_withFont:n { X } } }
+                        ^ {
+                            \__mhchem_output_scriptWithFont:n {#4#6}
+                          }
+                      }
                   }
               }
           }
       }
+    \group_end:
+  }
+\cs_new_protected:Npn \__mhchem_output_withFont:n #1
+  {
+    \bool_if:NTF \l__mhchem_output_isMathMode_bool
+      { \__mhchem_output_escapeFromMathToRomanMath:n {#1} }
+      { \__mhchem_output_escapeFromMathToText:n {#1} }
+  }
+\cs_new_protected:Npn \__mhchem_output_scriptWithFont:n #1
+  {
+    \int_compare:nT
+      { \l__mhchem_option_version_int > 3 }
+      {
+        \thinmuskip=0mu
+        \medmuskip=0mu
+        \thickmuskip=0mu
+      }
+    \bool_if:NTF \l__mhchem_output_isMathMode_bool
+      {
+        \int_compare:nTF
+          { \l__mhchem_option_version_int < 2 }
+          {#1}
+          { \__mhchem_output_escapeFromMathToRomanMath:n {#1} }
+      }
+      { \__mhchem_output_escapeFromMathToText:n {#1} }
+  }
+\cs_new_protected:Npn \__mhchem_output_escapeFromMathToText:n #1
+  { \text { \mhchem@hook@beforeText #1 } }
+\cs_new_protected:Npn \__mhchem_output_escapeToRomanMath:n #1
+  {
+    \bool_if:NTF \l__mhchem_output_isMathMode_bool
+      { \__mhchem_output_escapeFromMathToRomanMath:n {#1} }
+      { \__mhchem_output_escapeFromTextToRomanMath:n {#1} }
+  }
+\cs_new_protected:Npn \__mhchem_output_escapeFromTextToRomanMath:n #1
+  { \ensuremath { \__mhchem_output_escapeFromMathToRomanMath:n {#1} } }
+\cs_new_protected:Npn \__mhchem_output_escapeFromMathToRomanMath:n #1
+  { \mhchem@option@mathFont { \mhchem@hook@beforeRomanMath #1 } }
+\cs_new_protected:Npn \__mhchem_output_escapeFromTextToItalicText:n #1
+  { \group_begin: \itshape \mhchem@hook@beforeItalicText #1 \group_end: \/ }
+\cs_new_protected:Npn \__mhchem_output_escapeToItalicMath:n #1
+  {
+    \ensuremath { \__mhchem_output_escapeFromMathToItalicMath:n {#1} }
+  }
+\cs_new_protected:Npn \__mhchem_output_escapeFromMathToItalicMath:n #1
+  {
+    \text { \__mhchem_output_escapeFromTextToItalicMath:n {#1} }
+  }
+\cs_new_protected:Npn \__mhchem_output_escapeFromTextToItalicMath:n #1
+  {
+    \ensuremath
+      {
+        \mhchem@hook@beforeItalicMath
+        \bool_if:NT \l__mhchem_cg_isScript_bool
+          {
+            \medmuskip=0mu
+            \thinmuskip=0mu
+            \thickmuskip=0mu
+          }
+        #1
+      }
+  }
+\cs_new_protected:Npn \__mhchem_output_minus:
+  {
+    \bool_if:NTF \l__mhchem_output_isMathMode_bool
+      { - }
+      { \mhchem@option@textminus }
+  }
+\cs_new_protected:Npn \__mhchem_output_plus:
+  {
+    \bool_if:NTF \l__mhchem_output_isMathMode_bool
+      { {}+{} }
+      { \hspace{0.5ex} + \hspace{0.5ex} }
+  }
+\cs_new_protected:Npn \__mhchem_output_operatorPlus:
+  {
+    \int_compare:nTF { \l__mhchem_option_version_int < 4 }
+      { \ensuremath { {}+{} } }
+      { \__mhchem_output_plus: }
+  }
+\cs_new_protected:Npn \__mhchem_output_operatorEquals:
+  {
+    \int_compare:nTF { \l__mhchem_option_version_int < 4 }
+      { {}={} }
+      {
+        \bool_if:NTF \l__mhchem_output_isMathMode_bool
+          { {}={} }
+          { \hspace{0.5ex} = \hspace{0.5ex} }
+      }
+  }
+\cs_new_protected:Npn \__mhchem_output_electronDot:
+  {
+    \bool_if:NTF \l__mhchem_output_isMathMode_bool
+      { \mhchem@option@textElectronDot }
+      { \mhchem@option@textElectronDot }
+  }
+\cs_new_protected:Npn \__mhchem_output_additionCompound:
+  {
+    \ensuremath { \,{\mhchem@option@cdot}\, }
+  }
+\cs_new_protected:Npn \__mhchem_output_excited:
+  {
+    \bool_if:NTF \l__mhchem_output_isMathMode_bool
+      { \ast }
+      { \smash{\raisebox{-0.4em}{\scalebox{1.3}{*}}} }
+  }
+\cs_new_protected:Npn \__mhchem_output_commaDecimal:
+  { \__mhchem_output_withFont:n { , } }
+\cs_new_protected:Npn \__mhchem_output_commaEnumeration:
+  { \__mhchem_output_withFont:n { , } \ensuremath { \mkern3mu } }
+\cs_new_protected:Npn \__mhchem_output_commaAuto:
+  {
+    \__mhchem_regex_peek:nTF { [0-9] }
+      { \__mhchem_output_commaDecimal: }
+      { \__mhchem_output_commaEnumeration: }
+  }
+\cs_new_protected:Npn \__mhchem_output_commaEnumerationSmall:
+  { \__mhchem_output_withFont:n { , } \ensuremath { \mkern1mu } }
+\cs_new_protected:Npn \__mhchem_output_commaAutoSmall:
+  {
+    \__mhchem_regex_peek:nTF { [0-9] }
+      { \__mhchem_output_commaDecimal: }
+      { \__mhchem_output_commaEnumerationSmall: }
+  }
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%   bonds   %%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+\newlength\mhchem@bondwidth%
+\newlength\mhchem@bondheight%
+\newlength\mhchem@smallbondwidth@tmpA%
+\newlength\mhchem@smallbondwidth@tmpB%
+\newlength\mhchem@smallbondwidth%
+\newlength\mhchem@bondtmp@minussidebearingleft
+\newlength\mhchem@bondtmp@minussidebearingright
+
+\def\mhchem@setbondwidth{%
+  \int_compare:nTF { \l__mhchem_option_version_int < 4 }
+    {
+      \setlength\mhchem@bondtmp@minussidebearingleft{\mhchem@option@minusmathsidebearingleft}
+      \setlength\mhchem@bondtmp@minussidebearingright{\mhchem@option@minusmathsidebearingright}
+    }
+    {
+      \bool_if:NTF \l__mhchem_output_isMathMode_bool
+        {
+          \setlength\mhchem@bondtmp@minussidebearingleft{\mhchem@option@minusmathsidebearingleft}
+          \setlength\mhchem@bondtmp@minussidebearingright{\mhchem@option@minusmathsidebearingright}
+        }
+        {
+          \setlength\mhchem@bondtmp@minussidebearingleft{\mhchem@option@minustextsidebearingleft}
+          \setlength\mhchem@bondtmp@minussidebearingright{\mhchem@option@minustextsidebearingright}
+        }
+    }
+  \setlength\mhchem@bondwidth{\widthof{\sbond}}%
+  \setlength\mhchem@bondheight{\heightof{\sbond}}%
+  \setlength\mhchem@smallbondwidth@tmpA{%
+    \mhchem@bondwidth-\mhchem@bondtmp@minussidebearingleft-\mhchem@bondtmp@minussidebearingright}%
+  \setlength\mhchem@smallbondwidth@tmpB{%
+    \widthof{\sbond\sbond\sbond}-\mhchem@bondtmp@minussidebearingleft-%
+    \mhchem@bondtmp@minussidebearingright}%
+  \setlength\mhchem@smallbondwidth{\mhchem@bondwidth*%
+    \ratio{\mhchem@smallbondwidth@tmpA}{\mhchem@smallbondwidth@tmpB}}%
+}
+\def\mhchem@halfbond{\rlap{\hspace{\mhchem@bondtmp@minussidebearingleft}%
+                     \resizebox{\mhchem@smallbondwidth}{\mhchem@bondheight}{\sbond}\unskip%
+                     \resizebox{\mhchem@smallbondwidth}{\mhchem@bondheight}{\sbond}%
+                     \resizebox{\mhchem@smallbondwidth}{\mhchem@bondheight}{\sbond}}%
+                     \phantom{\sbond}}%
+
+\cs_new_protected:Npn \__mhchem_output_sbond:
+  {
+    \int_compare:nTF { \l__mhchem_option_version_int < 4 }
+      { {\ensuremath{-}} }
+      {
+        \bool_if:NTF \l__mhchem_output_isMathMode_bool
+          { {\ensuremath{-}} }
+        { \text{\mhchem@option@textminus} }
+      }
   }
 
 \ExplSyntaxOff
 
-%%% @mathbox
-\newcommand*\mhchem@mathbox[2][]{%
-  \mathchoice%
-    {\mhchem@mathbox@ii{\displaystyle}{#1}{#2}}%
-    {\mhchem@mathbox@ii{\textstyle}{#1}{#2}}%
-    {\mhchem@mathbox@ii{\scriptstyle}{#1}{#2}}%
-    {\mhchem@mathbox@ii{\scriptscriptstyle}{#1}{#2}}}%
-\newlength\mhchem@mathbox@tmp@i
-\newlength\mhchem@mathbox@tmp@ii
-\newcommand*\mhchem@mathbox@ii[3]{%
-  \setlength{\mhchem@mathbox@tmp@i}{\widthof{\ensuremath{#1#2}}}%
-  \setlength{\mhchem@mathbox@tmp@ii}{\widthof{\ensuremath{#1#3}}}%
-  \ifdim\mhchem@mathbox@tmp@i<\mhchem@mathbox@tmp@ii%
-    \mhchem@mathbox@i{#3}%
-  \else%
-    \makebox[\mhchem@mathbox@tmp@i]{\ensuremath{#1#3}}%
-  \fi}
-\newcommand*\mhchem@mathbox@i[1]{\mathchoice%
-  {\mbox{\ensuremath{\displaystyle#1}}}%
-  {\mbox{\ensuremath{\textstyle#1}}}%
-  {\mbox{\ensuremath{\scriptstyle#1}}}%
-  {\mbox{\ensuremath{\scriptscriptstyle#1}}}}
+\ExplSyntaxOn % with special tilde
+\char_set_catcode_letter:n { 126 } % tilde
+
+\cs_new_protected:Npn \mhchem@bond #1
+  {
+    \ensuremath
+      {
+        \str_case:nnn {#1}
+          {
+            { - } { \sbond }
+            { 1 } { \sbond }
+            { = } { \dbond }
+            { 2 } { \dbond }
+            { ## } { \tbond }
+            { 3 } { \tbond }
+            { ~ }
+              {
+                \mhchem@setbondwidth
+                \mhchem@halfbond
+              }
+            { ~- }
+              {
+                \mhchem@setbondwidth
+                \rlap{\protect\raisebox{.2ex}{\mhchem@halfbond}}
+                \protect\raisebox{-.2ex}{\sbond}
+              }
+            { ~-- }
+              {
+                \mhchem@setbondwidth
+                \rlap{\protect\raisebox{.4ex}{\mhchem@halfbond}}
+                \rlap{\sbond}
+                \protect\raisebox{-.4ex}{\sbond}
+              }
+            { ~= }
+              {
+                \mhchem@setbondwidth
+                \rlap{\protect\raisebox{.4ex}{\mhchem@halfbond}}
+                \rlap{\sbond}
+                \protect\raisebox{-.4ex}{\sbond}
+              }
+            { -~- }
+              {
+                \mhchem@setbondwidth
+                \rlap{\protect\raisebox{.4ex}{\sbond}}
+                \rlap{\mhchem@halfbond}
+                \protect\raisebox{-.4ex}{\sbond}
+              }
+            { ... } { {\cdot}{\cdot}{\cdot} }
+            { .... } { {\cdot}{\cdot}{\cdot}{\cdot} }
+            { -> } { {\rightarrow} }
+            { <- } { {\leftarrow} }
+          }
+          {
+            \PackageError{mhchem}{Unknown~bond~type~in~\string\bond~(#1)}%
+          }
+      }
+  }
+\ExplSyntaxOff  % end of Expl with tilde
 
 %%% @mathboxright
 \newcommand*\mhchem@mathboxright[2]{\mathchoice%
@@ -2881,11 +3004,24 @@
 
 \def\mhchem@option@mathFont{\mathrm}
 \def\mhchem@option@textFont{}
-\bool_new:N \__mhchem_option_superscriptsStacked_bool
+\def\mhchem@hook@beforeCe{}
+\def\mhchem@hook@afterCe{}
+\def\mhchem@hook@beforeText{}
+\def\mhchem@hook@beforeItalicText{}
+\def\mhchem@hook@beforeRomanMath{}
+\def\mhchem@hook@beforeItalicMath{}
+\bool_new:N \l__mhchem_option_layoutWasSet
+\bool_set_false:N \l__mhchem_option_layoutWasSet
+\bool_new:N \l__mhchem_option_superscriptsStacked_bool
+\bool_new:N \l__mhchem_option_subscriptsDeep_bool
+\cs_new_protected:Npn \mhchem@option@textElectronDot {}
+\cs_new_protected:Npn \mhchem@option@cdot {}
+\bool_new:N \l__mhchem_option_greekSelectedByUser
+\bool_set_false:N \l__mhchem_option_greekSelectedByUser
 
 \keys_define:nn {mhchem}
   {
-    version .int_set:N = \__mhchem_option_version_int,
+    version .int_set:N = \l__mhchem_option_version_int,
     version .value_required:,
     version .initial:n = { -1 },
     version .default:n = { -1 },
@@ -2897,25 +3033,50 @@
     font .choice:,
     font / sf .code:n =
       {
-        \def\mhchem@option@textFont{\sffamily}%
-        \def\mhchem@option@mathFont{\mathsf}%
+        \def\mhchem@option@textFont{\sffamily}
+        \def\mhchem@option@mathFont{\mathsf}
       },
     font / .code:n =
       {
-        \def\mhchem@option@textFont{}%
-        \def\mhchem@option@mathFont{\mathrm}%
+        \def\mhchem@option@textFont{}
+        \def\mhchem@option@mathFont{\mathrm}
       },
 
-    minus-sidebearing-left .dim_set:N = \mhchem@option@minussidebearingleft,
-    minus-sidebearing-left .initial:n = { 0.06em },
-    minus-sidebearing-right .dim_set:N = \mhchem@option@minussidebearingright,
-    minus-sidebearing-right .initial:n = { 0.11em },
+    layout .choice:,
+    layout / stacked .code:n =
+      {
+        \bool_set_true:N \l__mhchem_option_layoutWasSet
+        \bool_set_true:N \l__mhchem_option_superscriptsStacked_bool
+      },
+    layout / staggered-deep .code:n =
+      {
+        \bool_set_true:N \l__mhchem_option_layoutWasSet
+        \bool_set_false:N \l__mhchem_option_superscriptsStacked_bool
+        \bool_set_true:N \l__mhchem_option_subscriptsDeep_bool
+      },
+    layout / staggered-flat .code:n =
+      {
+        \bool_set_true:N \l__mhchem_option_layoutWasSet
+        \bool_set_false:N \l__mhchem_option_superscriptsStacked_bool
+        \bool_set_false:N \l__mhchem_option_subscriptsDeep_bool
+      },
+
+    minus-sidebearing-left .dim_set:N = \mhchem@option@minusmathsidebearingleft,
+    minus-sidebearing-right .dim_set:N = \mhchem@option@minusmathsidebearingright,
+    minus-math-sidebearing-left .dim_set:N = \mhchem@option@minusmathsidebearingleft,
+    minus-math-sidebearing-left .initial:n = { 0.06em },
+    minus-math-sidebearing-right .dim_set:N = \mhchem@option@minusmathsidebearingright,
+    minus-math-sidebearing-right .initial:n = { 0.11em },
+    minus-text-sidebearing-left .dim_set:N = \mhchem@option@minustextsidebearingleft,
+    minus-text-sidebearing-left .initial:n = { 0.10em },
+    minus-text-sidebearing-right .dim_set:N = \mhchem@option@minustextsidebearingright,
+    minus-text-sidebearing-right .initial:n = { 0.16em },
 
     arrows .choice:,
     arrows / font .code:n = { \mhchem@definearrows{#1} },
     arrows / pgf .code:n =
       {
-        \bool_if:NT { \__mhchem_option_inPreamble_bool }
+        \bool_if:NT { \l__mhchem_option_inPreamble_bool }
           {
             \RequirePackage{pgf}
             \RequirePackage{tikz}
@@ -2924,7 +3085,7 @@
       },
     arrows / pgf-filled .code:n =
       {
-        \bool_if:NT { \__mhchem_option_inPreamble_bool }
+        \bool_if:NT { \l__mhchem_option_inPreamble_bool }
           {
             \RequirePackage{pgf}
             \RequirePackage{tikz}
@@ -2940,51 +3101,56 @@
     skip-after-amount .initial:n = { \, },
 
     textminus .code:n = { \def\mhchem@option@textminus{#1} },
-    textminus .initial:n = { -- },
+    textminus .initial:n = { \hspace{0.3ex} -- \hspace{0.3ex} },
 
-    textcdot .code:n = { \def\mhchem@option@textcdot{#1} },
-    textcdot .initial:n = { \cdot },
+    cdot .code:n = { \def\mhchem@option@cdot{#1} },
+    cdot .initial:n = { \cdot },
+    textelectrondot .code:n = { \cs_set_protected:Npn \mhchem@option@textElectronDot {#1} },
+    textelectrondot .initial:n =
+      {
+        \int_compare:nTF { \l__mhchem_option_version_int < 4 }
+          { \ensuremath{\textbf{\fontfamily{cmr}\selectfont\textperiodcentered}} }
+          { \ensuremath { \bullet } }
+      },
 
-    superscripts .choice:,
-    superscripts / stacked .code:n =
-      { \bool_set_true:N \__mhchem_option_superscriptsStacked_bool },
-    superscripts / shifted .code:n =
-      { \bool_set_true:N \__mhchem_option_superscriptsStacked_bool },
-    superscripts / .code:n =
-      { \bool_set_true:N \__mhchem_option_superscriptsStacked_bool },
-    superscripts .initial:n .code:n =
-      { \bool_set_true:N \__mhchem_option_superscriptsStacked_bool },
   }
 
 \newcommand*\mhchemoptions[1]
   { \keys_set:nn { mhchem } {#1} }
 
-\bool_new:N \__mhchem_option_inPreamble_bool
-\bool_set_true:N \__mhchem_option_inPreamble_bool
+\bool_new:N \l__mhchem_option_inPreamble_bool
+\bool_set_true:N \l__mhchem_option_inPreamble_bool
 \ProcessKeysPackageOptions{mhchem}
-\bool_set_false:N \__mhchem_option_inPreamble_bool
+\bool_set_false:N \l__mhchem_option_inPreamble_bool
 
-\int_compare:nT { -1 = \__mhchem_option_version_int }
+\int_compare:nT { -1 = \l__mhchem_option_version_int }
   {
     \msg_error:nn { mhchem } { options / no-version }
-    \int_set:Nn \__mhchem_option_version_int { 3 }
+    \int_set:Nn \l__mhchem_option_version_int { 4 }
   }
 % else
   {
-    \int_compare:nT { \__mhchem_option_version_int > 3}
+    \int_compare:nT { \l__mhchem_option_version_int > 4 }
       {
         \msg_warning:nn { mhchem } { options / version-too-high }
       }
   }
+\bool_if:NF \l__mhchem_option_layoutWasSet
+  {
+    \int_compare:nTF { \l__mhchem_option_version_int < 4 }
+      { \mhchemoptions{layout=staggered-deep} }
+      { \mhchemoptions{layout=staggered-flat} }
+  }
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%   legacy   %%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-\int_compare:nT { \__mhchem_option_version_int < 4 }
+\int_compare:nT { \l__mhchem_option_version_int < 4 }
   {
-    \newcommand*\mhchem@cmath[1]{\ensuremath{\text{\ensuremath{#1}}}}%
+    \newcommand*\mhchem@cmath[1]{\__mhchem_output_escapeFromMathToItalicMath:n{#1}}
     \newcommand*\cmath[1]{\mhchem@cmath{#1}}
     \DeclareRobustCommand\cf[2][]{\mhchem@cf[#1]{#2}}
+    \DeclareRobustCommand\cee[1]{\mhchem@cee{#1}}
   }