From fc358ce7332053945afe16ced2a271556cdccfb7 Mon Sep 17 00:00:00 2001
From: Norbert Preining <norbert@preining.info>
Date: Tue, 4 Feb 2020 03:01:28 +0000
Subject: CTAN sync 202002040301

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+% !arara: pdflatex
+% !arara: biber
+% arara: pdflatex: { action: nonstopmode }
+% arara: pdflatex: { action: nonstopmode }
+% --------------------------------------------------------------------------
+% the CHEMMACROS package
+%
+%   comprehensive support for typesetting chemistry documents
+%
+% --------------------------------------------------------------------------
+% Clemens Niederberger
+% --------------------------------------------------------------------------
+% https://github.com/cgnieder/chemmacros/
+% contact@mychemistry.eu
+% --------------------------------------------------------------------------
+% If you have any ideas, questions, suggestions or bugs to report, please
+% feel free to contact me.
+% --------------------------------------------------------------------------
+% Copyright 2011--2020 Clemens Niederberger
+%
+% This work may be distributed and/or modified under the
+% conditions of the LaTeX Project Public License, either version 1.3
+% of this license or (at your option) any later version.
+% The latest version of this license is in
+%   http://www.latex-project.org/lppl.txt
+% and version 1.3 or later is part of all distributions of LaTeX
+% version 2005/12/01 or later.
+%
+% This work has the LPPL maintenance status `maintained'.
+%
+% The Current Maintainer of this work is Clemens Niederberger.
+% --------------------------------------------------------------------------
+\documentclass{chemmacros-manual}
+
+\DeclareAcronym{ghs}{
+  short     = ghs ,
+  long      = Globally Harmonized System of Classification and Labelling of
+    Chemicals ,
+  pdfstring = GHS ,
+  accsupp   = GHS
+}
+\DeclareAcronym{eu}{
+  short     = EU ,
+  long      = European Union ,
+  pdfstring = EU ,
+  accsupp   = EU
+}
+\DeclareAcronym{iupac}{
+  short     = iupac ,
+  long      = International Union of Pure and Applied Chemistry ,
+  pdfstring = IUPAC ,
+  accsupp   = IUPAC
+}
+\DeclareAcronym{UN}{
+  short     = un ,
+  long      = United Nations ,
+  pdfstring = UN ,
+  accsupp   = UN
+}
+\DeclareAcronym{dvi}{
+  short     = dvi ,
+  long      = device independent file format ,
+  pdfstring = DVI ,
+  accsupp   = DVO
+}
+\DeclareAcronym{pdf}{
+  short     = pdf ,
+  long      = portable document file ,
+  pdfstring = PDF ,
+  accsupp   = PDF
+}
+\DeclareAcronym{id}{
+  short     = id ,
+  long      = identification string ,
+  pdfstring = ID ,
+  accsupp   = ID
+}
+
+\chemsetup{
+  modules = {all,polymers} ,
+  greek = newtx ,
+  formula = chemformula ,
+  chemformula/format = \libertineLF
+}
+
+\sisetup{
+  detect-mode=false,
+  mode=text,
+  text-rm=\libertineLF
+}
+
+\defbibheading{bibliography}{\section{References}}
+\addbibresource{\jobname.bib}
+\addbibresource{cnltx.bib}
+
+\begin{filecontents*}[overwrite]{\jobname.bib}
+@book{iupac:greenbook,
+  author    = {E. Richard Cohan and Tomislav Cvita\v{s} and Jeremy G. Frey and
+    Bertil Holmstr\"om and Kozo Kuchitsu and Roberto Marquardt and Ian Mills and
+    Franco Pavese and Martin Quack and J\"urgen Stohner and Herbert L. Strauss and
+    Michio Takami and Anders J Thor} ,
+  title     = {``Quantities, Symbols and Units in Physical Chemistry'', \acs{iupac}
+    Green Book} ,
+  shorttitle = {The \acs{iupac} Green Book} ,
+  sorttitle = {Quantities, Symbols and Units in Physical Chemistry} ,
+  indexsorttitle = {Quantities, Symbols and Units in Physical Chemistry} ,
+  edition   = {3rd Edition. 2nd Printing} ,
+  year      = {2008} ,
+  publisher = {\acs{iupac} \&\ RSC Publishing, Cambridge}
+}
+@book{iupac:redbook,
+  author    = {Neil G. Connelly and Ture Damhus and Richard M. Hartshorn and
+    Alan T. Hutton} ,
+  title     = {``Nomenclature of Inorganic Chemistry'', \acs{iupac} Red Book} ,
+  shorttitle = {The \acs{iupac} Red Book} ,
+  sorttitle = {Nomenclature of Inorganic Chemistry} ,
+  indexsorttitle = {Nomenclature of Inorganic Chemistry} ,
+  year      = {2005} ,
+  publisher = { \acs{iupac} \&\ RSC Publishing, Cambridge} ,
+  isbn      = {0-85404-438-8}
+}
+@book{iupac:bluebook,
+  author    = {R. Panico and W. H. Powell and J-C. Richer},
+  title     = {``Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F,
+    and H'', \acs{iupac} Blue Book},
+  shorttitle = {The \acs{iupac} Blue Book} ,
+  sorttitle = {Nomenclature of Organic Chemistry} ,
+  indexsorttitle = {Nomenclature of Organic Chemistry} ,
+  edition   = {\mkbibacro{draft}},
+  date      = {2004-10-07},
+  url       =
+  {http://old.iupac.org/reports/provisional/abstract04/BB-prs310305/CompleteDraft.pdf},
+  urldate   = {2013-07-07}
+}
+@misc{eu:ghsystem_regulation,
+  author   = {{The European Parliament and The Council of the European Union}},
+  sortname = {European Parliament and The Council of the European Union} ,
+  title    = {Regulation (EC) No 1272/2008 of the European Parliament and of
+    the Council} ,
+  subtitle = {on classification, labelling and packaging of substances and
+    mixtures, amending and repealing Directives 67/548/EEC and 1999/45/EC, and
+    amending Regulation (EC) No 1907/2006} ,
+  journal  = {Official Journal of the European Union} ,
+  date     = {2008-12-16}
+}
+@online{unece:ghsystem_implementation,
+  author   = {{United Nations Economic Commission for Europe}} ,
+  title    = {GHS Implementation} ,
+  url      =
+    {http://www.unece.org/trans/danger/publi/ghs/implementation_e.html} ,
+  urldate  = {2012-03-20} ,
+  date     = {2012-03-20}
+}
+@online{mychemistry:chemmacros-dev,
+  author  = {Clemens Niederberger} ,
+  title   = {chemmacros development} ,
+  url     = {http://www.mychemistry.eu/2015/06/chemmacros-development/} ,
+  urldate = {2015-07-16} ,
+  date    = {2015-06-14}
+}
+@online{mychemistry:modular-chemmacros,
+  author  = {Clemens Niederberger} ,
+  title   = {modular chemmacros} ,
+  url     = {http://www.mychemistry.eu/2015/06/modular-chemmacros/} ,
+  urldate = {2015-07-16} ,
+  date    = {2015-06-08}
+}
+@online{mychemistry:chemmacros-update-how,
+  author  = {Clemens Niederberger} ,
+  title   = {a new chemmacros -- but how?} ,
+  url     = {http://www.mychemistry.eu/2015/07/a-new-chemmacros-but-how/} ,
+  urldate = {2015-07-16} ,
+  date    = {2015-07-15}
+}  
+\end{filecontents*}
+
+\DeclareInstance{xfrac}{chemformula-text-frac}{text}
+  {
+    scale-factor        = 1 ,
+    denominator-bot-sep = -.2ex ,
+    denominator-format  = \scriptsize #1 ,
+    numerator-top-sep   = -.2ex ,
+    numerator-format    = \scriptsize #1 ,
+    slash-right-kern    = .05em ,
+    slash-left-kern     = .05em
+  }
+
+\usetikzlibrary{calc,positioning,decorations.pathmorphing,patterns}
+
+% \newpackagename\chemmacros{chemmacros}
+\newcommand*\chemmacrosversion{\csname c_chemmacros_version_tl\endcsname}
+\newpackagename\chemformula{chemformula}
+\newpackagename\ghsystem{ghsystem}
+\newpackagename\chemgreek{chemgreek}
+
+\renewcommand*\AmS{\hologo{AmS}}
+\newcommand*\TikZ{Ti\textit{k}Z}
+\newcommand*\tablehead[1]{\textrm{\bfseries#1}}
+
+\providecommand*\XyM{%
+  X\kern-.30em
+  \smash{\raise.50ex\hbox{\char'7}}%
+  \kern-.30em M%
+}
+\providecommand*\XyMTeX{\XyM\kern-.1em\TeX}
+
+% \NewChemPhase{\aqi}{aq,$\infty$}% aqueous solution at infinite dilution
+% \NewChemPhase{\cd}{cd}% condensed phase
+% \NewChemPhase{\lc}{lc}% liquid crystal
+
+\newname\hensel{Martin Hensel}
+\newname\pedersen{Bj\o rn Pedersen}
+
+\newcommand*\iupaccs[3][]{%
+  \command{#2}[\quad\iupac{\csuse{#2}}]
+    #3\ifblank{#1}{}{\ifblank{#3}{}{ }An alias for this command is \cs{#1}.}%
+}
+
+% \undef\module
+% \undef\moduleidx
+\newidxcmd\chemmodule{\code{#1}}[ (module)]
+\newidxcmd\tikzdecoration{\code{#1}}[ (\TikZ\ decoration)]
+\AtEndPreamble{%
+  \pdfstringdefDisableCommands{%
+    \def\chemmodule*#1{\textquotedblleft#1\textquotedblright}%
+  }%
+}
+\newidxcmd\sym{\code{#1}}[ (symbol)]
+
+\makeatletter
+\def\cnltx@bash@listings@style{
+  language         = bash,
+  basicstyle       = {\sourceformat\color{black}},
+  % numbers          = left,
+  % numberstyle      = \tiny,
+  xleftmargin      = 1em,
+  numbersep        = .75em,
+  gobble           = \cnltx@gobble ,
+  columns          = fullflexible,
+  literate         =
+    {ä}{{\"a}}1
+    {ö}{{\"o}}1
+    {ü}{{\"u}}1
+    {Ä}{{\"A}}1
+    {Ö}{{\"O}}1
+    {Ü}{{\"U}}1
+    {ß}{{\ss}}1 ,
+  breaklines       = true,
+  keepspaces       = true,
+  breakindent      = 1em,
+  commentstyle     = \color{comment},
+  keywordstyle     = \color{black}\bfseries ,
+  stringstyle      = \color{black} ,
+  showstringspaces = false ,
+  morekeywords     = texdoc
+}
+
+\cnltx@expandargs(nx)\lstdefinestyle
+  {bash}
+  {\expandonce\cnltx@bash@listings@style}
+
+\newcommand*\prompt{}
+\patchcmd\lst@NewLine
+  {\hbox{}}% search
+  {\hbox{}\prompt}% replace
+  {}% success
+  {}% failure
+\newsourcecodeenv[
+  code-only,
+  sourcecode-options = {
+    style = bash ,
+    deleteindex = [5][keyword5] ,
+    deleteindex = [6][keyword6]
+  },
+  pre-code           = \def\prompt{\textasciitilde\space\$\space}  
+]{lbash}
+\makeatother
+
+\renewcommand*\dictumauthorformat[1]{#1}
+\renewcommand*\raggeddictumtext{}
+
+\newcommand*\TF{\textcolor{red}{\uline{\code{\textcolor{cs}{\textit{TF}}}}}}
+
+\makeatletter
+\newrobustcmd*\explcsformat[1]{%
+  \code{\textbackslash\textcolor{cs}{\detokenize{#1}}}%
+}
+\newidxcmd\explcs{\explcsformat{#1}}[ (expl3)]
+
+\cnltx@deflistitem{\cnltx@explcommand}{\explcs}
+\renewenvironment{commands}
+  {%
+    \let\command\cnltx@command
+    \let\explcommand\cnltx@explcommand
+    \cnltxlist
+  }
+  {\endcnltxlist}
+\newenvironment{tikzcode}
+  {%
+    \def\arrowtip{\@cnltx@option@item\code}%
+    \cnltxlist
+  }
+  {\endcnltxlist}
+
+\newrobustcmd*\showenv[1]{\beginenv*\code{\{}\env{#1}\code{\}}}
+\makeatother
+
+\ExplSyntaxOn
+\cs_new_protected:Npn \chemboldchecks #1
+  {
+    \seq_set_map:NNn \l_tmpa_seq \l__chemmacros_if_bf_seq { \code {##1} }
+    \seq_use:Nnnn \l_tmpa_seq {,~} {,~} {~#1~}
+  }
+\ExplSyntaxOff
+
+\AtBeginDocument{\renewcommand*\reftextfaraway[1]{starting on page~\pageref{#1}}}
+
+\usepackage{bookmark}
+
+\begin{document}
+
+\part{Preliminaries}
+\section{Licence, Requirements and \textsc{README}}\label{sec:licence-requ-readme}
+\license
+
+\chemmacros\ loads the packages \pkg{expl3}~\cite{bnd:l3kernel} and
+\pkg{xparse}~\cite{bnd:l3packages}.  Depending on your usage other packages
+will be loaded.  They are mentioned when the corresponding module using the
+package is described.
+
+\section{Motivation and Background}\label{sec:motiv-backgr}
+This package grew from a small collection of personal helper macros back
+in~2010 into a rather big package supporting various different chemical
+typesetting tasks.  I hope I have achieved the following points with this
+package:
+\begin{itemize}
+  \item Intuitive usage as far as the syntax of the commands is concerned.
+  \item A comprehensive set of macros! If there are any needs you might have
+    with respect to typesetting of chemistry which is not supported by this
+    package\footnote{Not including needs already solved by other packages such
+      as \pkg{chemnum} or \pkg{chemfig}.} then let me know so \chemmacros\ can
+    be extended.
+  \item The commands shall not only make typesetting easier and faster but
+    also the document source more readable with respect to semantics
+    (\code{\cs{ortho}-dichlorobenzene} is easier to read and understand than
+    \code{\cs*{textit}\Marg{o}-dichlorobenzene}); the first variant in my
+    opinion also is more in the spirit of \LaTeXe.
+  \item As much customizability as I could think of so every user can adapt
+    the commands to his or her own wishes.  Every now and then users have
+    wishes which can't be solved with the available options.  Almost always
+    I'll add options then.  If you find something please contact me, see
+    section~\vref{sec:sugg-bug-reports}.
+  \item Default settings that are compliant with the recommendations of the
+    \acf{iupac}.
+\end{itemize}
+Especially the last point in the past needed some pushing from users to get
+things right in many places.  If you find anything not compliant with
+\ac{iupac} recommendations please contact me, see
+section~\vref{sec:sugg-bug-reports}.  Don't forget to add references for the
+corresponding \ac{iupac} recommendation.
+
+\section{The Structure of \chemmacros}\label{sec:structure-chemmacros}
+\subsection{General Structure}
+Since version~5.0 the \chemmacros\ package has a strictly modular
+structure\sinceversion{5.0}.  On the one hand this eases maintenance but it
+will also allow for easy and quick extension in the future.  In a way it is a
+logical consequence from \chemmacros' history: since version~2.0, \ie, since
+the fall of~2011 \chemmacros\ already had modular options.
+
+The different modules of \chemmacros\ are divided into two groups:
+\begin{enumerate}
+  \item Internal modules which provide underlying functionality or basic
+    functionality which is not of direct interest from a user perspective but
+    might be if you plan to write a module yourself (see
+    section~\ref{sec:own-modules} for details).
+  \item User modules which provide all the stuff for typesetting.
+\end{enumerate}
+Both groups each are subdivided into two groups: preloaded modules and modules
+which have to be loaded by the programmer (internal modules) or by the
+document author (user modules).  Those modules are described in
+parts~\ref{part:preloaded-modules} (preloaded modules)
+and~\ref{part:additional-modules} (additional modules) of this manual.
+
+The above means that not all functionality is available per default.  If you
+want to load \emph{all} modules no matter what then you can say:
+\begin{sourcecode}
+  \usechemmodule{all}
+\end{sourcecode}
+or
+\begin{sourcecode}
+  \chemsetup{modules=all}
+\end{sourcecode}
+which will load all modules which are part of \chemmacros\ (also see
+section~\vref{sec:all-module}). Own modules (see
+section~\vref{sec:own-modules}) are \emph{not} loaded through this, though,
+and still have to be loaded additionally.
+
+In part~\vref{part:preloaded-modules} the preloaded modules are described,
+first the user modules then the internal ones, in
+part~\vref{part:additional-modules} the other available modules are described,
+again the user modules first.  In each section the modules are described in
+an alphabetical order.
+
+\subsection{Using \chemmacros' Options}\label{sec:using-chemm-opti}
+Prior to v5.0 \chemmacros\ had quite a number of package options.
+\chemmacros\ v5.0 or higher has none!  All of \chemmacros' options are set
+using the command
+\begin{commands}
+  \command{chemsetup}[\oarg{module}\marg{option list}]
+    \chemmacros' setup command.
+\end{commands}
+
+When an option is described then in the left margin the module the option
+belongs to is denoted.  This looks something like this:
+\begin{options}
+  \keyval{option}{value}\Module{module}\Default
+    Description of \option{option}. The module is printed in the left margin.
+    The default value to the right is the setting the option has when
+    \chemmacros\ is loaded.  This can be an explicit setting but the option
+    can also be empty.
+  \keychoice{choice-option}{list,of,\default{choices}}\Module{module}\Default{list}
+    Description of \option{choice-option}.  A choice option can only be used
+    with a predefined list of values. If one of the values is underlined it
+    means that the option can be used without value in which case the
+    underlined value is chosen.  If no value is underlined then a value
+    \emph{has} to be given by the user.
+  \keybool{boolean-option}\Module{module}\Default{true}
+    Description of \option{boolean-option}.  A boolean option is a choice
+    option with exactly the two values \code{true} and \code{false}.  If the
+    option is called without value then the underlined value is chosen (which
+    is always \code{true} for a boolean option).
+\end{options}
+
+An option or list of options belonging to a module \chemmodule{module} can be
+set in two ways:
+\begin{sourcecode}
+  % first possibility:
+  \chemsetup[module]{
+    option1 = value ,
+    option2 = value
+  }
+  % second possibility:
+  \chemsetup{
+    module/option1 = value ,
+    module/option2 = value
+  }
+\end{sourcecode}
+The second way allows to set options belonging to different modules with one
+call of \cs{chemsetup}.
+
+\subsection{Support Package \chemformula}
+\chemformula\ provides means of typesetting chemical formulas and reactions.
+You will see its macros \cs{ch} and \cs{chcpd} every now and then in this
+manual.  When using \chemmacros\ you can consider the \chemformula\
+package~\cite{pkg:chemformula} to be loaded as \chemmacros\ makes use of it in
+various places.  \chemmacros\ and \chemformula\ are tightly intertwined.
+Nevertheless you should be able to use the \pkg{mhchem}~\cite{pkg:mhchem}
+package with \chemmacros. Please see section~\vref{sec:using-mhchem} for
+details and \latin{caveat}s.  \emph{The recommendation is to use
+  \chemformula.}
+
+A historical note: \chemformula\ started as a part of \chemmacros\ in
+January~2012.  Since July~2013 it is a completely independent package -- from
+\chemformula's point of view.  It is maintained independently and has a manual
+of its own.
+
+\subsection{Upgrading from version $<5.0$}
+People upgrading from versions $<5.0$ will find that almost everything they
+know from earlier versions is the same in versions $\geq5.0$.  But there are
+important and \emph{breaking} differences:
+\begin{itemize}
+  \item \chemmacros\ has no package options any more, all options are set via
+    \cs{chemsetup}, also see section~\vref{sec:using-chemm-opti}.
+  \item Not all of the features are available per default any more, for some
+    the corresponding module has to be loaded explicitly, see
+    section~\ref{sec:general-options}.  If suddenly some commands or
+    environments seem to be undefined this is the most likely reason.
+  \item Some option modules have been renamed (\eg, \module*{iupac} is now
+    \module{nomenclature}).  If you experience strange errors when you upgrade
+    your document this is the most likely source.
+  \item The command family \cs*{NewChem\ldots}, \cs*{RenewChem\ldots} and
+    \cs*{DeclareChem\ldots} has a new member \cs*{ProvideChem\ldots}.
+  \item In \cs{iupac} the macro \cs*{-} no longer gives a dash with breaking
+    point.  Instead \sym*{-} can be used directly\footnote{\cs*{-} is provided
+      up to and including v5.2 but is dropped in higher versions.}.
+  \item The macro \cs{ox} has another default behaviour (\keyis{pos}{super})
+    and the starred version has another effect (\keyis{pos}{top}) than the
+    same macro in earlier versions.  Now the default behaviour follows
+    \acs{iupac} recommendations.  A second change is that the atom is now
+    treated as a \chemformula\ input (this depends on the setting of the
+    \option{formula} option, see~\vref{sec:chemformula-module}).
+  \item The syntax of \cs{NewChemReaction} and friends is now different from
+    what it used to be.  If you have defined your own reaction environments
+    you need to adapt!
+  \item \chemmacros\ offers a macro \cs{state} which is similar to but
+    different from the earlier macro \cs*{State}.  \cs*{State} is deprecated.
+    There are also differences in the syntax of \cs{enthalpy} \vs\ the earlier
+    \cs*{Enthalpy}, \cs{entropy} \vs\ \cs*{Entropy} and \cs{gibbs} \vs\
+    \cs*{Gibbs}.  The uppercase versions are deprecated. The  macro
+    \cs{NewChemState} also has a different syntax now.
+  \item At various places in the code improvements and fixes have been made,
+    too many to list them here.  You should keep an open eye and first of all
+    read the manual closely.
+\end{itemize}
+
+\subsection{Compatibility Mode}
+
+\subsubsection{For Users}
+It is actually not true that \chemmacros' has no package options any more.  It
+has one very important package option:
+\begin{options}
+  \keychoice{compatibility}{\meta{version},newest,latest}\Default{\chemmacrosversion}
+    Let's you specify the version of \chemmacros\ you want to use.  Any
+    version earlier than 5.0 will load v4.7. \ie, the last version before
+    \chemmacros\ got its modular structure\footnote{Mostly: the loaded v4.7
+      has got a few fixes}.  Not using the option will always load the newest
+    version.
+
+    Both values \code{newest} and \code{latest} will choose the latest version
+    available.
+\end{options}
+
+In your document you can check for the compatibility mode.  For the following
+functions it is important to understand the rules: \emph{greater} means
+\emph{newer}.  The version number is \emph{not} a usual decimal number!  The
+syntax for \meta{version} is \meta{major}\code{.}\meta{minor}\meta{optional
+  subrelease}.  This means that a version~5.11 is \emph{newer} than a
+version~5.7!  In the same way \emph{less} means \emph{older}.  As last
+example: 5.10~is \emph{newer} (greater) than~5.1.  \meta{optional subrelease}
+is a lowercase letter which might or might not be present in a version number.
+Version~5.7b is newer than~5.7a which in turn is newer than~5.7.
+\begin{commands}
+  \expandable\command{IfChemCompatibilityTF}[\marg{comp}\marg{version}%
+  \marg{true}\marg{false}]
+    Checks the value given through the option \option{compatibility} against
+    \meta{version} using \meta{comp} and either leaves \meta{true} or
+    \meta{false} in the input stream. \meta{comp} can be one of \code{<},
+    \code{<=}, \code{=}, \code{>=} or \code{>}.
+  \expandable\command{IfChemCompatibilityT}[\marg{comp}\marg{version}\marg{true}]
+    Checks the value given through the option \option{compatibility} against
+    \meta{version} using \meta{comp} and leaves \meta{true} in the input
+    stream if the check is logically true.  \meta{comp} can be one of
+    \code{<}, \code{<=}, \code{=}, \code{>=} or \code{>}.
+  \expandable\command{IfChemCompatibilityF}[\marg{comp}\marg{version}\marg{false}]
+    Checks the value given through the option \option{compatibility} against
+    \meta{version} using \meta{comp} and leaves \meta{false} in the input
+    stream if the check is logically false.  \meta{comp} can be one of
+    \code{<}, \code{<=}, \code{=}, \code{>=} or \code{>}.
+\end{commands}
+
+A possible usage:
+\begin{sourcecode}
+  \IfChemCompatibilityT{>=}{5.0}{\usechemmodule{all}}
+\end{sourcecode}
+
+Loading \chemmacros\ with \keyis{compatibility}{4.7} also allows to use the
+package options from that version:
+\begin{sourcecode}
+  \usepackage[compatibility=4.7,language=german]{chemmacros}
+\end{sourcecode}
+
+\subsubsection{For Module Writers}
+For future versions the aim is not to make such breaking changes again.  While
+we never know what the future actually will bring \chemmacros\ now has the
+tools for tying code to a version number:
+\begin{commands}
+  \expandable\explcommand{chemmacros_if_compatibility:nn}[\TF\ \marg{comp}
+  \marg{version} \marg{true} \marg{false}]
+    expl3 version of \cs{IfChemCompatibilityTF}.
+\end{commands}
+
+In modules one can try adding code for a certain version or range of versions:
+\begin{commands}
+  \command{ChemCompatibility}[\marg{version} \meta{code} \cs{EndChemCompatibility}]
+    Leaves \meta{code} in the input stream if the compatibility version $x$
+    given by \option{compatibility} matches \meta{version}
+    ($x=\text{\meta{version}}$).
+  \command{ChemCompatibilityFrom}[\marg{version} \meta{code} \cs{EndChemCompatibility}]
+    Leaves \meta{code} in the input stream if the compatibility version $x$
+    given by \option{compatibility} matches \meta{version} or newer.  This
+    means \meta{version} is the \emph{oldest} version allowed
+    ($x\geq\text{\meta{version}}$).
+  \command{ChemCompatibilityTo}[\marg{version} \meta{code} \cs{EndChemCompatibility}]
+    \changedversion{5.8a}Leaves \meta{code} in the input stream if the
+    compatibility version $x$ given by \option{compatibility} matches any
+    version up to and \emph{excluding} \meta{version}. This means
+    \meta{version} is the \emph{oldest} version \emph{not} allowed
+    ($x<\text{\meta{version}}$).
+  \command{ChemCompatibilityBetween}[\marg{version 1}\marg{version 2} \meta{code}
+  \cs{EndChemCompatibility}]
+    \changedversion{5.8a}Leaves \meta{code} in the input stream if the
+    compatibility version $x$ given by \option{compatibility} lies between and
+    \emph{including} \meta{version 1} up to and \emph{excluding} \meta{version 2}
+    ($\text{\meta{version 1}}\leq x<\text{\meta{version 2}}$).
+  \command{EndChemCompatibility}
+    This macro \emph{must} end each of the \cs*{ChemCompatibility\ldots}
+    macros.
+\end{commands}
+
+You may refer to the current version of \chemmacros\ with the following
+tokenlists:
+\begin{commands}
+  \explcommand{c_chemmacros_date_tl}
+    The current release date: \enquote{\csname
+      c_chemmacros_date_tl\endcsname}.
+  \explcommand{c_chemmacros_version_major_number_tl}
+    The current major version: \enquote{\csname
+    c_chemmacros_version_major_number_tl\endcsname}.
+  \explcommand{c_chemmacros_version_minor_number_tl}
+    The current minor version: \enquote{\csname
+    c_chemmacros_version_minor_number_tl\endcsname}.
+  \explcommand{c_chemmacros_version_number_tl}
+    The current version number: \enquote{\csname
+    c_chemmacros_version_number_tl\endcsname}.
+  \explcommand{c_chemmacros_version_subrelease_tl}
+    The current sub-release: \enquote{\csname
+    c_chemmacros_version_subrelease_tl\endcsname}.
+  \explcommand{c_chemmacros_version_tl}
+    The current version: \enquote{\csname c_chemmacros_version_tl\endcsname}.
+  \explcommand{c_chemmacros_info_tl}
+    The package information: \enquote{\csname
+      c_chemmacros_info_tl\endcsname}.
+\end{commands}
+
+\section{General Options}\label{sec:general-options}
+
+\chemmacros\ has some core options which don't belong to any of the modules
+described in parts~\ref{part:preloaded-modules}
+and~\ref{part:additional-modules}.  Those options have no module denoted in
+the left margin next to their descriptions and are also set without specifying
+a module:
+\begin{sourcecode}
+  \chemsetup{
+    option1 = value ,
+    option2 = value
+  }
+\end{sourcecode}
+
+Two of those options are explained now:
+\begin{options}
+  \keyval{modules}{comma separated list of module names}\Default
+    With this option you can specify which modules you want to load.
+    Alternatively you can use \cs{usechemmodule}\marg{comma separated list of
+      module names}.
+  \keyval{greek}{mapping}\Default
+    Explicitly specify which mapping should be used by the \chemgreek\
+    package~\cite{pkg:chemgreek}.  For details about what this means please
+    refer to section~\vref{sec:greek-module}.
+\end{options}
+
+Some internal modules may also define core options, \eg, the \chemmodule{lang}
+module, see section~\vref{sec:lang-module}.
+
+\part{The Preloaded Modules}\label{part:preloaded-modules}
+
+\section{User Modules}
+\subsection{The \chemmodule*{acid-base} Module}\label{sec:acid-base-module}
+
+Easy representation of \pH, \pKa \ldots
+\begin{commands}
+  \command{pH} \pH
+  \command{pOH} \pOH
+  \command{Ka} \Ka, depends on language settings, see
+    section~\vref{sec:lang-module}.  The translations can be adapted.
+  \command{Kb} \Kb
+  \command{Kw} \Kw
+  \command{pKa}[\oarg{num}] \cs{pKa}: \pKa, \cs{pKa}\Oarg{1}: \pKa[1], depends
+    on language settings, see  section~\vref{sec:lang-module}.  The translations
+    can be adapted.
+  \command{pKb}[\oarg{num}] \cs{pKb}: \pKb, \cs{pKb}\Oarg{1}: \pKb[1]
+  \command{p}[\marg{anything}] \eg\ \cs{p}\Marg{\cs{Kw}} \p{\Kw}
+\end{commands}
+
+\begin{example}[side-by-side]
+  \Ka\ \Kb\ \pKa\ \pKa[1] \pKb\ \pKb[1]
+\end{example}
+
+\begin{cnltxquote}[{\citetitle{iupac:greenbook} \cite[][p.\,103]{iupac:greenbook}}]
+ The operator \p{} \textelp{} shall be printed in Roman type.
+\end{cnltxquote}
+
+There is one option which changes the style the \p{} is typeset, other options
+allow to change the subscript of the constants:
+\begin{options}
+  \keychoice{p-style}{italics,slanted,upright}\Module{acid-base}\Default{upright}
+    Set the style of the \p{} operator.
+  \keyval{K-acid}{text}\Module{acid-base}\Default{\cs{ChemTranslate}\Marg{K-acid}}
+    The subscript to \cs{Ka} and \cs{pKa}.
+  \keyval{K-base}{text}\Module{acid-base}\Default{\cs{ChemTranslate}\Marg{K-base}}
+    The subscript to \cs{Kb} and \cs{pKb}.
+  \keyval{K-water}{text}\Module{acid-base}\Default{\cs{ChemTranslate}\Marg{K-water}}
+    The subscript to \cs{Kw}.
+  \keyval{eq-constant}{text}\Module{acid-base}\Default{K}
+    The\sinceversion{5.4} symbol of the constants.
+\end{options}
+\begin{example}
+  \pH, \pKa \par
+  \chemsetup[acid-base]{p-style=slanted} \pH, \pKa \par
+  \chemsetup[acid-base]{p-style=italics} \pH, \pKa
+\end{example}
+
+As you can see the default subscripts of \cs{Kw}, \cs{Ka} and \cs{Kb} are
+lowercase letters.  The literature is inconclusive about if this is the right
+way or if uppercase letters should be preferred.  In textbooks the uppercase
+variant usually seems to be used while journals seem to prefer the lowercase
+variant.  \chemmacros' default follows the usage in
+\citetitle{iupac:greenbook}~\cite{iupac:greenbook}.  If you want to change
+this you have two possibilities:
+
+\begin{example}
+  % this works only in the preamble:
+  % \DeclareTranslation{English}{K-acid}{\mathrm{A}}% use your language here
+  % alternative:
+  \chemsetup{acid-base/K-acid=\mathrm{A}}% overwrites language dependent settings
+  \pKa
+\end{example}
+
+The\sinceversion{5.4} constants \Ka, \Kb, and \Kw\ were defined using the
+following commands:
+\begin{commands}
+  \command{NewChemEqConstant}[\marg{cs}\marg{name}\marg{subscript}]
+    Define the constant \meta{cs} with the name \meta{name} and the subscript
+    \meta{subscript}.  This also defines the default translation with the key
+    \meta{name} using \meta{subscript} as fallback translation (see
+    section~\vref{sec:lang-module} for details).  It also defines the option
+    \meta{name} for setting the subscript.
+  \command{RenewChemEqConstant}[\marg{cs}\marg{name}\marg{default appearance}]
+    The same as \cs{NewChemEqConstant} but renews an existing command.
+  \command{DeclareChemEqConstant}[\marg{cs}\marg{name}\marg{default appearance}]
+    The same as \cs{NewChemEqConstant} but overwrites existing commands.
+  \command{ProvideChemEqConstant}[\marg{cs}\marg{name}\marg{default appearance}]
+    The same as \cs{NewChemEqConstant} but doesn't throw an error if \meta{cs}
+    already exists.
+\end{commands}
+
+This is how \cs{Ka} is defined:
+\begin{sourcecode}
+  \NewChemEqConstant\Ka{K-acid}{\mathrm{a}}
+\end{sourcecode}
+
+\subsection{The \chemmodule*{charges} Module}\label{sec:charges-module}
+
+The \chemmodule{charges} module loads the module \chemmodule{chemformula}.
+
+\subsubsection{Charge Symbols}
+\begin{commands}
+  \command{fplus} \fplus\ formal positive charge
+  \command{fminus} \fminus\ formal negative charge
+  \command{scrp} \scrp\ scriptstyle positive charge (\eg, for usage in
+    \pkg{chemfig}'s~\cite{pkg:chemfig} formulas).
+  \command{scrm} \scrm\ scriptstyle negative charge (\eg, for usage in
+    \pkg{chemfig}'s formulas).
+  \command{fscrp} \fscrp\ scriptstyle formal positive charge (\eg, for usage
+    in \pkg{chemfig}'s formulas).
+  \command{fscrm} \fscrm\ scriptstyle formal negative charge (\eg, for usage
+    in \pkg{chemfig}'s formulas).
+  \command{fsscrp} \fsscrp\ scriptscriptstyle formal positive charge (\eg, for
+    usage in \pkg{chemfig}'s formulas).
+  \command{fsscrm} \fsscrm\ scriptscriptstyle formal negative charge (\eg, for
+    usage in \pkg{chemfig}'s formulas).
+\end{commands}
+
+\subsubsection{Ion Charges}\label{sec:ion-charges}
+Simple displaying of (real) charges.  It is worth noting that these commands
+really are relicts from a time when \chemmacros\ tried hard to be compliant
+with \pkg{mhchem} and \chemformula\ didn't exist, yet.  \textbf{They are still
+  provided for backwards compatibility but \emph{my recommendation is to use}
+  \cs{ch} (see the documentation of the \chemformula\
+  package~\cite{pkg:chemformula}) \emph{and forget about these commands:}}
+\begin{commands}
+  \command{pch}[\oarg{number}]
+    positive charge
+  \command{mch}[\oarg{number}]
+    negative charge
+  \command{fpch}[\oarg{number}]
+    formal positive charge
+  \command{fmch}[\oarg{number}]
+    formal negative charge
+\end{commands}
+\begin{example}[side-by-side]
+  A\pch\ B\mch[3] C\fpch[2] D\fmch
+\end{example}
+
+\subsubsection{Partial Charges and Similar Stuff}\label{sec:part-charg-simil}
+
+The next ones probably are seldomly needed but nevertheless useful:
+\begin{commands}
+  \command{delp} \delp\ partial positive charge
+  \command{delm} \delm\ partial negative charge
+  \command{fdelp} \fdelp\ partial formal positive charge
+  \command{fdelm} \fdelm\ partial formal negative charge
+\end{commands}
+
+These macros for example can be used with the \cs{ox} command (see
+section~\vref{sec:redox-module}) or with the \pkg{chemfig} package:
+\begin{example}
+  \chemsetup{
+    charges/circled = all,
+    redox/parse     = false,
+    redox/pos       = top
+  }
+  \ch{"\ox{\delp,H}" -{} "\ox{\delm,Cl}"} \hspace*{1cm}
+  \chemfig{\chemabove[3pt]{\lewis{246,Br}}{\delm}-\chemabove[3pt]{H}{\delp}}
+\end{example}
+
+\subsubsection{Charge Options}
+
+\begin{options}
+  \keychoice{circled}{formal,\default{all},none}\Module{charges}\Default{formal}
+    \chemmacros\ uses two different kinds of charges which indicate the usage
+    of real ($+/-$) and formal (\fplus/\fminus) charges.  The option
+    \code{formal} distinguishes between them, option \code{none} displays them
+    all without circle, option \code{all} circles all.
+  \keychoice{circletype}{chem,math}\Module{charges}\Default{chem}
+    This option switches between two kinds of circled charge symbols:
+    \cs{fplus} \fplus/\cs{fminus} \fminus\ (\code{chem}) and
+    \verbcode+$\oplus$+ $\oplus$/\verbcode+$\ominus$+ $\ominus$ (\code{math}).
+  \keyval{partial-format}{\LaTeX\ code}\Module{charges}\Default{\cs*{tiny}}
+    Code which formats the macros defined with \cs{NewChemPartialCharge} (see
+    section~\ref{sec:own-charge-macros}).
+\end{options}
+
+\subsubsection{Own Charge Macros}\label{sec:own-charge-macros}
+Just in case the existing macros don't fit you needs there are commands for
+defining new ones or modifying the existing ones.  These commands define
+macros like those described in section~\vref{sec:ion-charges}.
+
+\begin{commands}
+  \command{NewChemCharge}[\marg{cs}\marg{charge symbol}]
+    Defines a new macro \meta{cs}. Raises an error if \meta{cs} already
+    exists.
+  \command{RenewChemCharge}[\marg{cs}\marg{charge symbol}]
+    Redefines a new macro \meta{cs}. Raises an error if \meta{cs} doesn't
+    exist.
+  \command{DeclareChemCharge}[\marg{cs}\marg{charge symbol}]
+    Defines a macro \meta{cs}.  Silently overwrites \meta{cs} if it exists.
+  \command{ProvideChemCharge}[\marg{cs}\marg{charge symbol}]
+    Defines a new macro \meta{cs}.  Does nothing if \meta{cs} already exists.
+\end{commands}
+An example of usage is the definition of the existing ion charge macros:
+\begin{sourcecode}
+  \NewChemCharge\fpch{\fplus}
+  \NewChemCharge\fmch{\fminus}
+\end{sourcecode}
+
+These commands define macros like those described in
+section~\vref{sec:part-charg-simil}. 
+\begin{commands}
+  \command{NewChemPartialCharge}[\marg{cs}\marg{charge symbol}]
+    Defines a new macro \meta{cs}. Raises an error if \meta{cs} already
+    exists.
+  \command{RenewChemPartialCharge}[\marg{cs}\marg{charge symbol}]
+    Redefines a new macro \meta{cs}. Raises an error if \meta{cs} doesn't
+    exist.
+  \command{DeclareChemPartialCharge}[\marg{cs}\marg{charge symbol}]
+    Defines a macro \meta{cs}.  Silently overwrites \meta{cs} if it exists.
+  \command{ProvideChemPartialCharge}[\marg{cs}\marg{charge symbol}]
+    Defines a new macro \meta{cs}.  Does nothing if \meta{cs} already exists.
+\end{commands}
+An example of usage is the definition of the existing partial charge macros:
+\begin{sourcecode}
+  \NewChemPartialCharge\fdelp{\fplus}
+  \NewChemPartialCharge\fdelm{\fminus}
+\end{sourcecode}
+
+\subsection{The \chemmodule*{nomenclature} Module}\label{sec:nomenclature-module}
+
+The \chemmodule{nomenclature} module loads the \chemmodule{tikz} module.  It
+also loads the package \pkg{scrlfile} which is part of the
+\KOMAScript\ bundle~\cite{bnd:koma-script}.
+
+\subsubsection{The \cs*{iupac} Command}
+
+Similar to the \pkg{bpchem} package~\cite{pkg:bpchem} \chemmacros\ provides a
+command\footnote{The idea and initial implementation is shamelessly borrowed
+  from \pkg{bpchem} by \pedersen.} for typesetting \ac{iupac} names.  Why is
+that useful?  \ac{iupac} names can get very long.  So long indeed that they
+span over more than two lines, especially in two-column documents.  This means
+they must be allowed to be broken more than one time.  This is what the
+following command does.
+\begin{commands}
+  \command{iupac}[\marg{IUPAC name}]
+    Inside this command use \sym{\textbar} indicate a breaking point
+    \sym{\textasciicircum} as a shortcut for \cs*{textsuperscript}. \sym{-},
+    \sym{(} and \sym{)} allow words to be broken while still allow the rest of
+    word to be hyphenated, likewise \sym{[} and \sym{]}.
+\end{commands}
+
+\begin{example}
+  \begin{minipage}{.4\linewidth}
+    \iupac{%
+      Tetra|cyclo[2.2.2.1^{1,4}]-un|decane-2-dodecyl-%
+      5-(hepta|decyl|iso|dodecyl|thio|ester)%
+    }
+  \end{minipage}
+\end{example}
+
+The \cs{iupac} command is more of a semantic command.  In many cases you can
+achieve (nearly) the same thing by using \cs*{-} instead of \sym{\textbar},
+and \cs*{textsuperscript} instead of \sym{\textasciicircum} without
+\cs{iupac}.  There are some important differences, though:
+\begin{itemize}
+  \item The character \sym{-} inserts a small space before the hyphen and
+    removes a small space after it.  Also usually words with hyphens are only
+    allowed to break at the hyphen.  Inside \cs{iupac} the hyphen will not
+    prevent further hyphenation.  The amount of inserted space can be
+    customized.
+  \item The character \sym{\textbar} not only prevents ligatures but also
+    inserts a small space.  The amount of inserted space can be customized.
+  \item The characters \sym{(} and \sym{)} allow the word to be hyphenated and
+    don't prevent further hyphenation, likewise \sym{[} and \sym{]}.
+  \item \sinceversion{5.3}The character \sym{'} is printed as \cs{chemprime}.
+  \item \sinceversion{5.8c}The character \sym{=} is printed ad
+    \cs{nonbreakinghyphen}.
+\end{itemize}
+\begin{example}[side-by-side]
+  \huge\iupac{2,4-Di|chlor|pentan} \par
+  2,4-Dichlorpentan
+\end{example}
+\begin{commands}
+  \command{chemprime}
+    Prints\sinceversion{5.3} a prime character in superscript position.  It is
+    defined as \verbcode+\ensuremath{{}^{\prime}}+.
+  \command{nonbreakinghyphen}
+    Prints\sinceversion{5.8c} a hyphen which doesn't allow a linebreak after
+    it.  It is defined as \verbcode+\mbox{-}\nobreak\hspace{0pt}+.
+\end{commands}
+
+The spaces inserted by \sym{-} and \sym{\textbar} can be
+customized.
+\begin{options}
+  \keyval{hyphen-pre-space}{dim}\Module{nomenclature}\Default{.01em}
+    Set the space that is inserted before the hyphen set with \sym{-}.
+  \keyval{hyphen-post-space}{dim}\Module{nomenclature}\Default{-.03em}
+    Set the space that is inserted after the hyphen set with \sym{-}.
+  \keyval{break-space}{dim}\Module{nomenclature}\Default{.01em}
+    Set the space inserted by \sym{\textbar}.
+\end{options}
+
+The command \cs{iupac} serves another purpose, too, however.  Regardless of
+the setting of the \option{iupac} option (see below) all the commands
+presented in this section are always defined \emph{inside} \cs{iupac}.  Quite
+a number of the naming commands have very general names: \cs{meta}, \cs{D},
+\cs{E}, \cs{L}, \cs{R}, \cs{S}, \cs{trans} and so forth\footnote{Please read
+  section~\vref{sec:one-letter-commands} before you consider using the
+  one-letter commands}.  This means they either are predefined already (\cs{L}
+\L) or are easily defined by another package or class (the \pkg{cool} package
+defines both \cs{D} and \cs{E}, for example).  In order to give you control
+which commands are defined in which way, there is the option \option{iupac}:
+\begin{options}
+  \keychoice{iupac}{auto,restricted,strict}\Module{nomenclature}\Default{auto}
+    Take care of how \ac{iupac} naming commands are defined.
+\end{options}
+It has three modes:
+\begin{itemize}
+ \item \keyis{iupac}{auto}: if the commands are \emph{not} defined by any
+   package or class you're using they are available generally, otherwise only
+   \emph{inside} \cs{iupac}.
+ \item \keyis{iupac}{restricted}: all naming commands are \emph{only} defined
+   inside \cs{iupac}.  If the commands are defined by another package they of
+   course have that meaning outside.  They're not defined outside otherwise.
+ \item \keyis{iupac}{strict}: \chemmacros\ overwrites any other definition and
+   makes the commands available throughout the document.  Of course the
+   commands can be redefined (but only in the document body).  They will still
+   be available inside \cs{iupac} then.
+\end{itemize}
+Table~\vref{tab:iupac_modes} demonstrates the different modes.
+
+\begin{table}
+  \centering
+  \caption{Demonstration of \option*{iupac}'s modes.}\label{tab:iupac_modes}
+  \begin{tabular}{lccc}
+    \toprule
+                              & auto       & restricted & strict \\
+    \midrule
+      \cs{L}                  & \L         & \L         & \iupac{\L} \\
+      \cs{iupac}\Marg{\cs{L}} & \iupac{\L} & \iupac{\L} & \iupac{\L} \\
+      \cs{D}                  & \D         & ---        & \D \\
+      \cs{iupac}\Marg{\cs{D}} & \iupac{\D} & \iupac{\D} & \iupac{\D} \\
+    \bottomrule
+  \end{tabular}
+\end{table}
+
+\subsubsection{Macros Defined (Not Only) For Usage in \cs*{iupac}}
+
+\paragraph{One-letter Macros}\label{sec:one-letter-commands}
+For some of the macros explained in this section one-letter commands are
+defined -- with a \latin{caveat} in mind, though: they are not actively
+recommended.  One-letter commands seldomly have meaningful names and often
+they've also been defined by other packages.  This means they make
+collaboration more difficult than it needs to be and are a source for package
+conflicts.  \chemmacros\ solves the latter problem by only providing them
+inside the argument of \cs{iupac}.  The one exception \chemmacros\ makes is
+the command \cs{p} (for things like \pH) which is and will remain an official
+command (see section~\vref{sec:acid-base-module}).  For all other one-letter
+macros alternatives with more meaningful names exist.
+
+\paragraph{Greek Letters}\label{par:greek_letters}
+
+Greek letters in compound names are typeset upright.  Here are a few examples
+for the existing macros:
+\begin{commands}
+  \command{chemalpha}[\quad\chemalpha]
+    Upright lowercase alpha
+  \command{chembeta}[\quad\chembeta]
+    Upright lowercase alpha
+  \command{chemgamma}[\quad\chemgamma]
+    Upright lowercase alpha
+  \command{chemdelta}[\quad\chemdelta]
+    Upright lowercase alpha
+\end{commands}
+There exist two commands for each of the twenty-four Greek letters: a
+lowercase and an uppercase version (\cs{chemalpha} and \cs{chemAlpha}).  Those
+commands are actually provided by the \chemgreek\ package.  For more details
+read section~\vref{sec:greek-module} and also refer to \chemgreek's
+documentation.
+
+There are a number of one-letter commands that some people may find convenient
+to use which use above mentioned commands to print Greek letters inside
+\cs{iupac}.  They're listed in table~\vref{tab:iupac-greek-shortcuts}.
+
+\begin{table}
+  \centering
+  \caption{\acs*{iupac} shortcuts for Greek letters.}
+  \label{tab:iupac-greek-shortcuts}
+  \begin{tabular}{*9l}
+    \toprule
+      macro &
+        \cs{a} & \cs{b} & \cs{g} & \cs{d} &
+        \cs{k} & \cs{m} & \cs{n} & \cs{w} \\
+    \midrule
+      letter &
+        \iupac{\a} & \iupac{\b} & \iupac{\g} & \iupac{\d} &
+        \iupac{\k} & \iupac{\m} & \iupac{\n} & \iupac{\w} \\
+    \bottomrule
+  \end{tabular}
+\end{table}
+
+\begin{example}
+  \iupac{5\chemalpha-androstan-3\chembeta-ol} \par
+  \iupac{\chemalpha-(tri|chloro|methyl)-\chemomega
+    -chloro|poly(1,4-phenylene|methylene)}
+\end{example}
+
+\paragraph{Hetero Atoms and added Hydrogen}
+
+Attachments to hetero atoms and added hydrogen atoms are indicated by italic
+letters~\cite{iupac:greenbook}.  \chemmacros\ defines a few macros for the
+most common ones.
+\begin{commands}
+  \iupaccs[H]{hydrogen}{The italic H for hydrogen.}
+  \iupaccs[O]{oxygen}{The italic O for oxygen.}
+  \iupaccs[N]{nitrogen}{The italic N for nitrogen.}
+  \iupaccs[Sf]{sulfur}{The italic S for sulfur.}
+  \iupaccs[P]{phosphorus}{The italic P for phosphorus.}
+\end{commands}
+\begin{example}[side-by-side]
+  \iupac{\nitrogen-methyl|benz|amide}
+  
+  \iupac{3\hydrogen-pyrrole}
+  
+  \iupac{\oxygen-ethyl hexanethioate}
+\end{example}
+
+\paragraph{Cahn-Ingold-Prelog}\label{par:cip}
+\begin{commands}
+  \command{cip}[\marg{conf}]
+    Typeset Cahn-Ingol-Prelog descriptors, \eg: \cs{cip}\Marg{R,S}
+    \cip{R,S}. \meta{conf} may be a csv list of entries.
+  \iupaccs[R]{rectus}{The rectus descriptor.}
+  \iupaccs[S]{sinister}{The sinister descriptor.}
+\end{commands}
+
+Both these commands and the entgegen/zusammen descriptors get a small
+additional amount of kerning after the closing parenthesis.  This amount can
+be changed through the following option:
+\begin{options}
+  \keyval{cip-kern}{dim}\Module{nomenclature}\Default{.075em}
+    Set the amount of kerning after the closing parenthesis.
+\end{options}
+The entries typeset by and implemented with \cs{cip} can be customized
+further:
+\begin{options}
+  \keyval{cip-outer-format}{format}\Default{\cs*{upshape}}
+    \sinceversion{5.8}The format of parentheses and commas typeset by
+    \cs{cip}.
+  \keyval{cip-inner-format}{format}\Default{\cs*{itshape}}
+    \sinceversion{5.8}The format of the entries in \cs{cip}.  This format
+    works additive to the outer format.
+  \keyval{cip-number-format}{format}\Default{\cs*{itshape}}
+    \sinceversion{5.8}The format of numbers in \cs{cip}.  This format works
+    additive to the outer format and is applied to arabic figures only.
+\end{options}
+
+\paragraph{Fischer}
+\begin{commands}
+  \iupaccs[D]{dexter}{The dexter descriptor.}
+  \iupaccs[L]{laevus}{The laevus descriptor.}
+\end{commands}
+
+\paragraph{cis/trans, zusammen/entgegen, syn/anti \& tert}
+\begin{itemize}
+  \item \cs{cis}   \iupac{\cis} \quad \cs{trans} \iupac{\trans}
+  \item \cs{fac}   \iupac{\fac} \quad \cs{mer}   \iupac{\mer}
+  \item \cs{sin}   \iupac{\sin} \quad \cs{ter}   \iupac{\ter}
+  \item \cs{zusammen} \iupac{\zusammen} \quad \cs{entgegen} \iupac{\entgegen}
+  \item \cs{syn}   \iupac{\syn} \quad \cs{anti}  \iupac{\anti}
+  \item \cs{tert}  \iupac{\tert}
+\end{itemize}
+An alias for \cs{entgegen} is \cs{E} and an alias for \cs{zusammen} is
+\cs{Z}.
+
+\paragraph{ortho/meta/para}
+\begin{center}
+    \cs{ortho} \iupac{\ortho} \quad
+    \cs{meta}  \iupac{\meta} \quad
+    \cs{para}  \iupac{\para}
+\end{center}
+
+Although these commands are provided I like to cite
+\citetitle{iupac:bluebook}~\cite{iupac:bluebook}:
+
+\begin{cnltxquote}[{\cite[][p.\,90]{iupac:bluebook}}]
+  The letters \iupac{\ortho}, \iupac{\meta}, and \iupac{\para} have been used
+  in place of \textit{ortho}, \textit{meta}, and \textit{para}, respectively,
+  to designate the 1,2-, 1,3-, and 1,4- isomers of disubstituted benzene.
+  This usage is strongly discouraged and is not used in preferred \acs{iupac}
+  names.
+\end{cnltxquote}
+
+\paragraph{Absolute Configuration}
+\begin{commands}
+  \command{Rconf}[\oarg{letter}]
+    \cs{Rconf}: \Rconf \quad \cs{Rconf}\oarg{}: \Rconf[]
+  \command{Sconf}[\oarg{letter}]
+    \cs{Sconf}: \Sconf \quad \cs{Sconf}\oarg{}: \Sconf[]
+\end{commands}
+
+\paragraph{Coordination Chemistry}
+
+\chemmacros\ provides a few commands useful in coordination chemistry:
+\begin{commands}
+  \command{bridge}[\marg{num}\quad\bridge{3}]
+    Denote bridging ligand connection.
+  \command{hapto}[\marg{num}\quad\hapto{5}]
+    Denote hapticity.
+  \command{dento}[\marg{num}\quad\dento{2}]
+    Denote denticity.
+\end{commands}
+\begin{example}
+  Ferrocene = \iupac{bis(\hapto{5}cyclo|penta|dienyl)iron} \par
+  \iupac{tetra-\bridge{3}iodido-tetrakis[tri|methyl|platinum(IV)]}
+\end{example}
+
+Two options allow customization:
+\begin{options}
+  \keychoice{bridge-number}{sub,super}\Module{nomenclature}\Default{sub}
+    Appends the number as a subscript or superscript, depending on the choice.
+    The \ac{iupac} recommendation is the subscript~\cite{iupac:redbook}.
+  \keybool{coord-use-hyphen}\Module{nomenclature}\Default{true}
+    Append a hyphen to \cs{hapto}, \cs{dento} and \cs{bridge} or don't.
+\end{options}
+
+The default behaviour\sinceversion{5.8} of \cs{hapto} and \cs{dento} has
+changed with version~5.8 to follow \ac{iupac} recommendations.
+
+\paragraph{Examples}
+\begin{example}
+  \iupac{\dexter-Wein|s\"aure} =
+  \iupac{\cip{2S,3S}-Wein|s\"aure} \par
+  \iupac{\dexter-($-$)-Threose} =
+  \iupac{\cip{2S,3R}-($-$)-2,3,4-Tri|hydroxy|butanal} \par
+  \iupac{\cis-2-Butene} =
+  \iupac{\zusammen-2-Butene}, \par
+  \iupac{\cip{2E,4Z}-Hexa|diene} \par
+  \iupac{\meta-Xylol} =
+  \iupac{1,3-Di|methyl|benzene}
+\end{example}
+
+\subsubsection{Own \cs*{iupac} Macros And Shorthands}
+
+If you find any commands missing you can define them using
+\begin{commands}
+  \command{NewChemIUPAC}[\marg{cs}\marg{declaration}]
+    Define a new \ac{iupac} command that is in any case defined inside of
+    \cs{iupac} regardless if \meta{cs} is defined elsewhere already.
+  \command{ProvideChemIUPAC}[\marg{cs}\marg{declaration}]
+    Define a new \ac{iupac} command that is in any case defined inside of
+    \cs{iupac} regardless if \meta{cs} is defined elsewhere already only if
+    the corresponding \ac{iupac} macro is not defined, yet.
+  \command{RenewChemIUPAC}[\marg{cs}\marg{declaration}]
+    Redefine an existing \ac{iupac} command that is in any case defined inside
+    of \cs{iupac} regardless if \meta{cs} is defined elsewhere already.
+  \command{DeclareChemIUPAC}[\marg{cs}\marg{declaration}]
+    Define a new \ac{iupac} command that is in any case defined inside of
+    \cs{iupac} regardless if \meta{cs} is defined elsewhere already.  This
+    silently overwrites an existing \ac{iupac} macro definition.
+  \command{LetChemIUPAC}[\marg{cs1}\marg{cs2}]
+    Defines \meta{cs1} to be an alias of \meta{cs2}.
+\end{commands}
+A command defined in this way will obey the setting of the option
+\option{iupac}.  This means any existing command is only overwritten with
+\keyis{iupac}{strict}.  However, \cs{NewChemIUPAC} will \emph{not} change the
+definition of an existing \ac{iupac} naming command but issue an error if the
+\ac{iupac} naming command already exists.  \cs{DeclareChemIUPAC} \emph{will}
+overwrite an existing \ac{iupac} command.
+\begin{example}
+  \NewChemIUPAC\endo{\textsc{endo}}
+  \RenewChemIUPAC\anti{\textsc{anti}}
+  \iupac{(2-\endo,7-\anti)-2-bromo-7-fluoro|bicyclo[2.2.1]heptane}
+\end{example}
+
+\cs{RenewChemIUPAC} allows you to redefine the existing \ac{iupac} naming
+commands.
+\begin{example}[side-by-side]
+  \iupac{\meta-Xylol} \par
+  \RenewChemIUPAC\meta{\textup{m}}
+  \iupac{\meta-Xylol}
+\end{example}
+
+There's also a way for defining new \ac{iupac} shorthands or changing the
+existing ones:
+\begin{commands}
+  \command{NewChemIUPACShorthand}[\meta{shorthand token}\meta{control sequence}]
+    Defines a new \ac{iupac} shorthand.  Inside \cs{iupac} it will be equal to
+    using \meta{control sequence}.  This throws an error if \meta{shorthand
+      token} is already defined.
+  \command{RenewChemIUPACShorthand}[\meta{shorthand token}\meta{control sequence}]
+    Redefines an existing \ac{iupac} shorthand.  This throws an error if
+    \meta{shorthand token} is not defined, yet.
+  \command{DeclareChemIUPACShorthand}[\meta{shorthand token}\meta{control sequence}]
+    Defines a new \ac{iupac} shorthand or redefines an existing one.
+  \command{ProvideChemIUPACShorthand}[\meta{shorthand token}\meta{control sequence}]
+    Provides a new \ac{iupac} shorthand.  Does nothing if \meta{shorthand
+      token} is already defined.
+  \command{RemoveChemIUPACShorthand}[\meta{shorthand token}]
+    Deletes an existing \ac{iupac} shorthand.
+\end{commands}
+
+\subsubsection{Latin Phrases}
+
+\chemmacros\ provides a command for typesetting latin phrases:
+\begin{commands}
+  \command{latin}[\oarg{options}\marg{phrase}]
+    Typesets \meta{phrase} according to the option \option{format} described
+    below.
+  \command{insitu}[\quad\insitu]
+  \command{invacuo}[\quad\invacuo]
+  \command{abinitio}[\quad\abinitio]
+\end{commands}
+
+If you additionally load \pkg{chemstyle}~\cite{pkg:chemstyle} said package
+will \emph{not} define its own \cs{latin}.
+
+The last three commands mentioned above are defined through
+\begin{commands}
+  \command{NewChemLatin}[\marg{cs}\marg{phrase}]
+    Define a new latin phrase.  Gives an error if \meta{cs} already exists.
+  \command{DeclareChemLatin}[\marg{cs}\marg{phrase}]
+    Define a new latin phrase.  Silently redefined existing macros.
+  \command{RenewChemLatin}[\marg{cs}\marg{phrase}]
+    Redefine an existing latin phrase.  Gives an error if \meta{cs} doesn't
+    exist.
+  \command{ProvideChemLatin}[\marg{cs}\marg{phrase}]
+    Define a new latin phrase only if \meta{cs} doesn't exist.
+\end{commands}
+\begin{example}[side-by-side]
+  \NewChemLatin\ltn{latin text}\ltn
+\end{example}
+You can change the appearance with this option:
+\begin{options}
+  \keyval{format}{definition}\Module{nomenclature}\Default{\cs*{emph}}
+    \changedversion{5.7}Sets the format for the latin phrases.
+\end{options}
+
+\subsection{The \chemmodule*{particles} Module}\label{sec:particles-module}
+
+The \chemmodule{particles} module loads the modules \chemmodule{charges} and
+\chemmodule{chemformula}.
+
+\subsubsection{Provided Particle Macros}
+The \chemmodule{particles} defines a number of macros which can be used for
+typesetting common particles in the running text.  Most of them don't make
+much sense in \pkg{chemformula}~\cite{pkg:chemformula}'s \cs{ch}, though,
+which doesn't mean that they can't be used there, of course:
+\begin{center}
+  \cs{el} \el\ \cs{prt} \prt\ \cs{ntr} \ntr\ \cs{Hyd} \Hyd\ \cs{Oxo} \Oxo\
+  \cs{water} \water\ \cs{El} \El\ \cs{Nuc} \Nuc\ \cs{ba} \ba
+\end{center}
+All of these macros are defined using \pkg{chemformula}'s \cs{chcpd}.  The
+details are explained in section~\vref{sec:defin-own-part}.
+
+The macros \cs{Nuc} and \cs{ba} are special:  they have an optional argument
+for the following options:
+\begin{options}
+  \keychoice{elpair}{dots,dash,false}\Module{particles}\Default{false}
+    Determine how the electron pair of the nucleophiles is displayed.  The
+    electron pair is drawn using \chemformula's \cs{chlewis} macro.
+  \keyval{space}{dim}\Module{particles}\Default{.1em}
+    Sets\sinceversion{5.3} the space that is inserted between the electron
+    pair and the negative charge sign.
+\end{options}
+Both options can of course also be set with \cs{chemsetup}.
+
+\begin{example}[side-by-side]
+  \ba[elpair=dots] \Nuc[elpair=dash]
+ 
+  \chemsetup[particles]{elpair=false}
+  \ba\ \Nuc
+\end{example}
+
+\subsubsection{Defining Own Particle Macros}\label{sec:defin-own-part}
+
+There are two sets of macros, one for defining particles and one for defining
+nucleophiles.
+\begin{commands}
+  \command{NewChemParticle}[\marg{cs}\marg{formula}]
+    Defines a new macro \meta{cs}. \meta{formula} is any valid \chemformula\
+    input (this depends on the setting of the \option{formula} option,
+    see~\vref{sec:chemformula-module}).  Raises an error if \meta{cs} already
+    exists.
+  \command{RenewChemParticle}[\marg{cs}\marg{formula}]
+    Redefines a new macro \meta{cs}. \meta{formula} is any valid \chemformula\
+    input (this depends on the setting of the \option{formula} option,
+    see~\vref{sec:chemformula-module}).  Raises an error if \meta{cs} doesn't
+    exist.
+  \command{DeclareChemParticle}[\marg{cs}\marg{formula}]
+    Defines a macro \meta{cs}. \meta{formula} is any valid \chemformula\
+    input (this depends on the setting of the \option{formula} option,
+    see~\vref{sec:chemformula-module}).  Silently overwrites \meta{cs} if it
+    exists.
+  \command{ProvideChemParticle}[\marg{cs}\marg{formula}]
+    Defines a new macro \meta{cs}. \meta{formula} is any valid \chemformula\
+    input (this depends on the setting of the \option{formula} option,
+    see~\vref{sec:chemformula-module}).  Does nothing if \meta{cs} already
+    exists.
+\end{commands}
+An example of usage is the definition of the existing particle macros:
+\begin{sourcecode}
+  \NewChemParticle\el {e-}
+  \NewChemParticle\prt{p+}
+  \NewChemParticle\ntr{n^0}
+\end{sourcecode}
+
+The following set defines macros like \cs{Nuc}
+\begin{commands}
+  \command{NewChemNucleophile}[\marg{cs}\marg{formula}]
+    Defines a new macro \meta{cs}. \meta{formula} is any valid \chemformula\
+    input (this depends on the setting of the \option{formula} option,
+    see~\vref{sec:chemformula-module}). Note that \meta{formula} will get a
+    trailing negative charge! Raises an error if \meta{cs} already exists. 
+  \command{RenewChemNucleophile}[\marg{cs}\marg{formula}]
+    Redefines a new macro \meta{cs}. \meta{formula} is any valid \chemformula\
+    (this depends on the setting of the \option{formula} option,
+    see~\vref{sec:chemformula-module}).  Note that \meta{formula} will get a
+    trailing negative charge! Raises an error if \meta{cs} doesn't exist.
+  \command{DeclareChemNucleophile}[\marg{cs}\marg{formula}]
+    Defines a macro \meta{cs}. \meta{formula} is any valid \chemformula\
+    (this depends on the setting of the \option{formula} option,
+    see~\vref{sec:chemformula-module}).  Note that \meta{formula} will get a
+    trailing negative charge!  Silently overwrites \meta{cs} if it exists. 
+  \command{ProvideChemNucleophile}[\marg{cs}\marg{formula}]
+    Defines a new macro \meta{cs}. \meta{formula} is any valid \chemformula\
+    (this depends on the setting of the \option{formula} option,
+    see~\vref{sec:chemformula-module}).  Note that \meta{formula} will get a
+    trailing negative charge!  Does nothing if \meta{cs} already exists.
+\end{commands}
+An example of usage is the definition of the existing nucleophile macros:
+\begin{sourcecode}
+  \NewChemNucleophile\Nuc{Nu}
+  \NewChemNucleophile\ba {ba}
+\end{sourcecode}
+A macro defined this way will have an optional argument for the
+\option{elpair} option.
+
+\subsection{The \chemmodule*{phases} Module}\label{sec:phases-module}
+
+The \chemmodule{phases} module loads the \chemmodule{chemformula} modul.
+
+\subsubsection{Basics}
+
+These commands are intended to indicate the phase of a compound.
+\begin{center}
+  \cs{sld} \sld \quad \cs{lqd} \lqd \quad \cs{gas} \gas \quad \cs{aq} \aq
+\end{center}
+\begin{example}
+  \ch{C\sld{} + 2 H2O\lqd{} -> CO2\gas{} + 2 H2\gas}\par
+  To make it complete: NaCl\aq.
+\end{example}
+
+The \ac{iupac} recommendation to indicate the state of aggregation is to put
+it in parentheses after the compound \cite{iupac:greenbook}.  However, you
+might want to put it as a subscript which is also very common.
+
+\begin{cnltxquote}[{\citetitle{iupac:greenbook}~\cite[][p.\,54]{iupac:greenbook}}]
+  The \textelp{} symbols are used to represent the states of aggregation of
+  chemical species.  The letters are appended to the formula in parentheses
+  and should be printed in Roman (upright) type without a full stop (period).
+\end{cnltxquote}
+
+There are two options to customize the output:
+\begin{options}
+  \keychoice{pos}{side,sub}\Module{phases}\Default{side}
+    Switch the position of the phase indicator.
+  \keyval{space}{dim}\Module{phases}\Default{.1333em}
+    Change the default spacing between compound a phase indicator if
+    \keyis{pos}{side}. A \TeX\ dimension.
+\end{options}
+\begin{example}
+  \chemsetup[phases]{pos=sub}
+  \ch{C\sld{} + 2 H2O\lqd{} -> CO2\gas{} + 2 H2\gas}\par
+  To make it complete: NaCl\aq.
+\end{example}
+
+All those phase commands have an optional argument:
+\begin{example}[side-by-side]
+  \ch{H2O "\lqd[\SI{5}{\celsius}]"}
+\end{example}
+
+There is also a generic phase command:
+\begin{commands}
+  \command{phase}[\marg{phase}]
+    If you need a phase indicator just once or twice.  You can use it to
+    denote a phase for which there is no phase command, yet.
+\end{commands}
+
+\subsubsection{Define Own Phases}
+Depending on the subject of your document you might need to indicate other
+states of aggregation.  You can easily define them.
+\begin{commands}
+  \command{NewChemPhase}[\marg{cs}\marg{symbol}]
+    Define a new phase command.  See section~\vref{sec:lang-depend} for a way
+    to define language dependent settings.  Gives an error if \meta{cs}
+    already exists.
+  \command{DeclareChemPhase}[\marg{cs}\marg{symbol}]
+    Define a new phase command. See section~\vref{sec:lang-depend} for a way to
+    define language dependent settings.  Overwrites previous definitions of
+    \meta{cs}.
+  \command{RenewChemPhase}[\marg{cs}\marg{symbol}]
+    Redefine an existing phase command.  See section~\vref{sec:lang-depend} for
+    a way to define language dependent settings.  Gives an error if \meta{cs}
+    is not defined.
+  \command{ProvideChemPhase}[\marg{cs}\marg{symbol}]
+    Define a new phase command.  See section~\vref{sec:lang-depend} for a way
+    to define language dependent settings.  Does nothing if \meta{cs} is
+    already defined.
+\end{commands}
+
+\begin{example}
+  % preamble:
+  \NewChemPhase\aqi{aq,$\infty$} % aqueous solution at infinite dilution
+  \NewChemPhase\cd {cd} % condensed phase
+  \NewChemPhase\lc {lc} % liquid crystal
+  \ch{NaOH\aqi} \ch{H2O\cd} \ch{U\phase{cr}} \ch{A\lc}\par
+  \chemsetup[phases]{pos=sub}
+  \ch{NaOH\aqi} \ch{H2O\cd} \ch{U\phase{cr}} \ch{A\lc}
+\end{example}
+
+\subsubsection{Language Dependencies}\label{sec:lang-depend}
+For each phase command a translation into the custom language can be defined.
+If a phase is declared with \cs{NewChemPhase} no translation exists and
+for every \pkg{babel} language the literal string is used that was provided
+as a definition.  Let's say you define the phase
+\begin{sourcecode}
+  \NewChemPhase\liquid{l}
+\end{sourcecode}
+and want to add the German translation ``f\/l''.  Then you could do
+\begin{sourcecode}
+  \DeclareTranslation{German}{phase-liquid}{f\/l}
+\end{sourcecode}
+This way, when you use it in a German document using the appropriate
+\pkg{babel} option using \cs*{liquid} would correctly translate.  For this the
+package \pkg{translations}~\cite{pkg:translations} is used.  The \acs{id}
+always is \code{phase-\meta{csname}} where \meta{csname} is the name of the
+phase command you defined without leading backslash.
+
+See section~\vref{sec:lang-module} for predefined translations and general
+language options of \chemmacros.
+
+\subsection{The \chemmodule*{symbols} Module}\label{sec:symbols-module}
+
+The \chemmodule{symbols} module defines a few symbols chemists need now and
+then.  It loads the package \pkg{amstext}~\cite{pkg:amstext}.
+\begin{commands}
+  \command{transitionstatesymbol}
+    This is self-explaining: \transitionstatesymbol
+  \command{standardstate}
+    Again self-explaining: \standardstate
+  \command{changestate}
+    The uppercase delta used in \state[superscript=]{H} for example.
+\end{commands}
+
+\section{Internal Modules}
+\subsection{The \chemmodule*{base} Module}\label{sec:base-module}
+
+The \chemmodule{base} module is the core module of \chemmacros. It defines
+some tools which can (and should) be used in other modules.  This means this
+section is only interesting for you if you plan to write a module yourself
+(see section~\vref{sec:own-modules} for details).
+
+This module requires the packages \pkg{bm}~\cite{pkg:bm}, 
+\pkg{amstext}~\cite{pkg:amstext}, and \pkg{etoolbox}~\cite{pkg:etoolbox}.
+
+This module also provides \cs{chemsetup} and the option \option{modules}.
+
+It also provides a number of (expl3) macros which may be used in other
+modules. In the macro descriptions below \TF\ denotes that a \code{T}, an
+\code{F} and a \code{TF} variant exist.  In case of an expandable conditional
+(\expandablesymbol) also the predicate variant is available.
+\begin{commands}
+  \expandable\explcommand{chemmacros_if_loaded:nn}[\TF\
+  \Marg{package|class} \marg{name} \marg{true} \marg{false}]
+    Checks if package (or class) \meta{name} has been loaded. Also works after
+    begin document.
+  \expandable\explcommand{chemmacros_if_package_loaded:n}[\TF\ \marg{name}
+  \marg{true} \marg{false}]
+    Checks if package \meta{name} has been loaded. Also works after begin
+    document.
+  \expandable\explcommand{chemmacros_if_class_loaded:n}[\TF\ \marg{name}
+  \marg{true} \marg{false}]
+    Checks if class \meta{name} has been loaded. Also works after begin
+    document.
+  \explcommand{chemmacros_nobreak:}
+    Inserts a penalty of \num{10000}.
+  \explcommand{chemmacros_allow_break:}
+    Inserts a penalty of \num{0}.
+  \explcommand{chemmacros_skip_nobreak:N}[ \meta{skip/length variable}]
+    Insert a horizontal skip where a linebreak is disallowed.
+  \expandable\explcommand{chemmacros_if_is_int:n}[\TF\ \marg{input} \marg{true}
+  \marg{false}]
+    Checks if \meta{input} is an integer or something else.
+  \explcommand{chemmacros_if_bold:}[\TF\ \marg{true} \marg{false}]
+    Checks if the current font weight is one of \chemboldchecks{or}.
+  \explcommand{chemmacros_bold:n}[ \marg{text}]
+    Checks if the current font weight is bold and if yes places \meta{text} in
+    \cs*{textbf} if in text mode or in \cs*{bm} if in math mode.  If no
+    \meta{text} simply is placed in the input stream as is.
+  \explcommand{chemmacros_text:n}[ \marg{text}]
+    Ensures that \meta{text} is placed in text mode.
+  \explcommand{chemmacros_math:n}[ \marg{text}]
+    Ensures that \meta{text} is placed in math mode.
+  \explcommand{chemmacros_new_macroset:nnn}[ \marg{name} \marg{arg spec}
+  \marg{internal command call}]
+    \changedversion{5.3b}A command to define a set of macros
+    \cs*{NewChem\meta{name}}, \cs*{RenewChem\meta{name}},
+    \cs*{DeclareChem\meta{name}} and \cs*{ProvideChem\meta{name}} where the
+    first letter of \meta{name} is converted to uppercase, other letters are
+    kept unchanged. \meta{arg spec} is any valid argument specification for
+    \pkg{xparse}'s \\
+    \cs{DeclareDocumentCommand}~\cite{bnd:l3packages}. \meta{internal command
+      call} should be a macro which makes definitions \emph{without} error
+    checks, \ie, define new macros or redefine existing ones like \cs*{def}
+    does.  This macro just should get the arguments passed on to.  Have a look
+    at the example below.
+  \explcommand{chemmacros_new_environment_macroset:nnn}[ \marg{name} \marg{arg spec}
+  \marg{internal command call}]
+    Like \explcs{chemmacros_new_macroset:nnn} but for environments.
+  \command{NewChemMacroset}[\sarg\marg{name}\marg{arg spec}\marg{internal
+    command call}]
+    A non-expl3 version of \explcs{chemmacros_new_macroset:nnn} for \LaTeXe\
+    programmers.  The starred version calls
+    \explcs{chemmacros_new_environment_macroset:nnn}.
+  \explcommand{chemmacros_add_cleveref_support:nnnnn}[ \marg{counter}
+    \marg{singular} \marg{plural} \marg{uppercase singular} \marg{uppercase
+      plural}]
+    A\sinceversion{5.6} command to add suiting names for a counter for the
+    \pkg{cleveref} package's \cs*{cref} commands.  This command acts at the
+    end of the preamble and only if a user hasn't provided definitions with
+    \cs*{crefname} already.
+  \command{ChemCleverefSupport}[\marg{counter}\marg{singular}\oarg{uppercase
+    singular}\marg{plural}\oarg{uppercase plural}]
+    \sinceversion{5.6}\LaTeXe-version of
+    \explcs{chemmacros_add_cleveref_support:nnnnn}.
+  \explcommand{chemmacros_add_fancyref_support:nnn}[ \marg{prefix} \marg{name}
+    \marg{uppercase name}]
+    A\sinceversion{5.6} command to add suiting names for a counter for the
+    \pkg{fancyref} package's \cs*{fref} commands.  This command acts at the
+    end of the preamble and doesn't override definitions made by the users.
+  \command{ChemFancyrefSupport}[\marg{prefix}\marg{name}\oarg{uppercase name}]
+    \sinceversion{5.6}\LaTeXe-version of
+    \explcs{chemmacros_add_fancyref_support:nnnnn}.
+\end{commands}
+This is how the macros \cs{NewChemParticle}, \cs{RenewChemParticle},
+\cs{DeclareChemParticle} and \cs{ProvideChemParticle} were defined:
+\begin{sourcecode}
+  \NewChemMacroset {Particle} {mm}
+    { \chemmacros_define_particle:Nn #1 {#2} }
+\end{sourcecode}
+
+The following macros strictly speaking are not provided by the
+\chemmodule{base} module but this place fits best for their description.
+\begin{commands}
+  \expandable\explcommand{chemmacros_if_module_exist:n}[\TF\ \marg{module}
+  \marg{true} \marg{false}]
+    Checks if a file with the correct name for a module \meta{module} can be
+    found.
+  \expandable\explcommand{chemmacros_if_module_loaded:n}[\TF\ \marg{module}
+  \marg{true} \marg{false}]
+    Checks if the module \meta{module} has already been loaded or not.
+  \explcommand{chemmacros_load_module:n}[ \marg{module}]
+    Loads module \meta{module} if it hasn't been loaded, yet.
+  \explcommand{chemmacros_load_modules:n}[ \marg{csv list of modules}]
+    Loads every module in \meta{csv list of modules} if they haven't been
+    loaded, yet. This is the code level variant of \cs{usechemmodule}.
+  \explcommand{chemmacros_before_module:nn}[ \marg{module} \marg{code}]
+    Saves\sinceversion{5.1} \meta{code} and inserts it right before
+    \meta{module} is loaded.  If \meta{module} is never loaded then
+    \meta{code} is never inserted.  If \meta{module} already is loaded when
+    the command is used then \meta{code} also is never inserted.
+  \explcommand{chemmacros_after_module:nn}[ \marg{module} \marg{code}]
+    Saves\sinceversion{5.1} \meta{code} and inserts it right after
+    \meta{module} is loaded.  If \meta{module} is never loaded then
+    \meta{code} is never inserted.  If \meta{module} already is loaded when
+    the command is used then \meta{code} is inserted immediately.
+\end{commands}
+
+\subsection{The \chemmodule*{chemformula} Module}\label{sec:chemformula-module}
+
+The \chemmodule{chemformula} module loads the \pkg{amstext}
+package~\cite{pkg:amstext} and the \chemmodule{charges} module.
+
+\subsubsection{For Users}
+There are different packages which provide means for typesetting chemical
+formulas:
+\begin{itemize}
+  \item \pkg{chemformula}~\cite{pkg:chemformula}.  This is probably well known
+    to users of \chemmacros.
+  \item \pkg{mhchem}~\cite{pkg:mhchem}.  This is the \enquote{older brother} of
+    \chemformula.
+  \item \pkg{chemfig}~\cite{pkg:chemfig}.  The easiest and most complete of the
+    packages for drawing skeletal formulas.
+  \item \XyMTeX~\cite{pkg:xymtex}.  A very comprehensive alternative for
+    typesetting chemistry.
+\end{itemize}
+In order to help authors getting a consistent layout \chemmacros\ does not
+make a choice which package to use for typesetting formulas.  Although
+\chemformula\ is well tested and preferred users can choose other packages if
+they like.
+
+this is done with the following general option:
+\begin{options}
+  \keyval{formula}{method}\Default{chemformula}
+    This\sinceversion{5.1} option let's you choose how chemical formulas are
+    typeset.  Available methods are
+    \begin{itemize}
+      \item \pkg{chemformula}
+      \item \pkg{mhchem}
+      \item \pkg{chemist}\sinceversion{5.6} (from the \XyMTeX\ bundle)
+      \item \pkg{chemfig}\sinceversion{5.6}
+    \end{itemize}
+    The corresponding package with the same name is loaded.
+\end{options}
+If you explicitly set this option the corresponding package is loaded
+immediately and the method is set up.  Otherwise the option will be set by
+\chemmacros\ at the end of the preamble.
+
+If\sinceversion{5.2} you load a method package in a way that a unique choice
+is possible then \chemmacros\ will set the method accordingly if you haven't
+set the option by yourself.  If \emph{no} unique choice is possible
+\chemmacros\ will raise a warning and choose \pkg{chemformula} regardless if
+the package is loaded or not.  In this case if you want to use another method
+you'll have to choose manually. \emph{All automatic choices only happen at the
+  end of the preamble}.
+
+\paragraph{Using the \pkg*{chemformula} Package}
+If you set \keyis{formula}{chemformula} the \chemmodule{chemformula} module
+makes it possible that you can set all \chemformula\ options via the
+\cs{chemsetup} command using the module \module{chemformula}, for example:
+\begin{sourcecode}
+  \chemsetup[chemformula]{format=\sffamily}
+\end{sourcecode}
+
+Everywhere where \chemmacros\ typesets chemical formulas \chemformula's macros
+\cs{chcpd} or \cs{ch} are used, for example in the reaction environments
+provided by the \chemmodule{reactions} module.
+
+\emph{This method is the recommended choice!}
+
+\paragraph{Using the \pkg*{mhchem} Package}\sinceversion{5.1}\label{sec:using-mhchem}
+If you set \keyis{formula}{mhchem} the \chemmodule{chemformula} module makes
+it possible that you can set all of \pkg{mhchem}'s options via the
+\cs{chemsetup} command using the module \module{mhchem}, for example:
+\begin{sourcecode}
+  \chemsetup[mhchem]{format=\sffamily}
+\end{sourcecode}
+
+Everywhere where \chemmacros\ typesets chemical formulas \pkg{mhchem}'s macro
+\cs{ce} is used, for example in the reaction environments provided by the
+\chemmodule{reactions} module.
+
+There are some \latin{caveat}s if you use this method:
+\begin{itemize}
+  \item This method has not been extensively tested, yet.  There may be errors
+     and wrong output at unexpected places.
+  \item Using this method effectively disables the different values of the
+    \module{particles} option \option{elpair} (see
+    section~\ref{sec:particles-module}).
+  \item The different kinds of formal charges provided by the
+    \chemmodule{charges} module (see section~\ref{sec:ion-charges}) are
+    disabled.  Formal charges always use the math method now.
+  \item There may also be other incompatibilities (\eg, \pkg{mhchem} has it's
+    own method of setting upright Greek letters so it may or may not disable
+    \chemmacros' mechanism).
+\end{itemize}
+
+\paragraph{Using the \pkg*{chemfig} Package}\sinceversion{5.6}\label{sec:using-chemfig}
+Everywhere where \chemmacros\ typesets chemical formulas \pkg{chemfig}'s macro
+\cs{printatom} is used, for example in the reaction environments provided by
+the \chemmodule{reactions} module.
+
+There are some \latin{caveat}s if you use this method:
+\begin{itemize}
+  \item This method has not been extensively tested, yet.  There may be errors
+     and wrong output at unexpected places.
+  \item Using this method effectively disables the different values of the
+    \module{particles} option \option{elpair} (see
+    section~\ref{sec:particles-module}).
+  \item The different kinds of formal charges provided by the
+    \chemmodule{charges} module (see section~\ref{sec:ion-charges}) are
+    disabled.  Formal charges always use the math method now.
+  \item The reaction environments by the \chemmodule{reactions} module may
+    work only to a limited respect.  If you plan to use them consider using
+    methods \pkg{chemformula} or \pkg{mhchem} instead.
+\end{itemize}
+
+\paragraph{Using the \pkg*{chemist} Package}\sinceversion{5.6}\label{sec:using-chemist}
+Everywhere where \chemmacros\ typesets chemical formulas \pkg{chemist}'s macro
+\cs{ChemForm} is used, for example in the reaction environments provided by
+the \chemmodule{reactions} module.
+
+There are some \latin{caveat}s if you use this method:
+\begin{itemize}
+  \item This method has not been extensively tested, yet.  There may be errors
+     and wrong output at unexpected places.
+  \item Using this method effectively disables the different values of the
+    \module{particles} option \option{elpair} (see
+    section~\ref{sec:particles-module}).
+  \item The different kinds of formal charges provided by the
+    \chemmodule{charges} module (see section~\ref{sec:ion-charges}) are
+    disabled.  Formal charges always use the math method now.
+  \item The reaction environments by the \chemmodule{reactions} module may
+    work only to a limited respect.  If you plan to use them consider using
+    methods \pkg{chemformula} or \pkg{mhchem} instead\footnote{On the other
+      hand \XyMTeX\ (and especially the \pkg{chemist} package) provides quite
+      a number of chemical reaction environments itself.}.
+\end{itemize}
+
+\subsubsection{For Module Writers}
+
+There are two macros for module writers:
+\begin{commands}
+  \explcommand{chemmacros_chemformula:n}[ \marg{formula}]
+    This is only a wrapper for \cs{chcpd} or \cs{ce}.  It is recommended that
+    module writers use this macro (or a variant thereof) inside of
+    \chemmacros' macros whenever they want to display a chemical formula.
+    Writers who prefer traditional \LaTeXe\ programming over expl3 should use
+    \cs*{chemmacros@formula}.
+  \explcommand{chemmacros_reaction:n}[ \marg{reaction}]
+    This is only a wrapper for \cs{ch} or \cs{ce}.  It is recommended that
+    module writers use this macro (or a variant thereof) inside of
+    \chemmacros' macros whenever they want to display a chemical reaction.
+    Writers who prefer traditional \LaTeXe\ programming over expl3 should use
+    \cs*{chemmacros@reaction}.
+\end{commands}
+
+\subsection{The \chemmodule*{errorcheck} Module}\label{sec:errorcheck-module}
+The\sinceversion{5.2} \chemmodule{errorcheck} module provides some rudimentary
+support for giving users more meaningful messages when they use a command or
+environment provided by a module that they haven't loaded.
+
+\subsection{The \chemmodule*{greek} Module}\label{sec:greek-module}
+
+The \chemmodule{greek} module loads the \pkg{chemgreek}
+package~\cite{pkg:chemgreek}.
+
+This module provides one option:
+\begin{options}
+  \keyval{greek}{mapping}
+    A valid value is any valid \chemgreek\ \meta{mapping}.  \chemmacros\ will
+    warn you if no mapping has been chosen or if you are using the
+    \code{default} or the \code{var-default} mapping because this means that
+    no upright Greek letters are available.
+\end{options}
+If you load a \chemgreek\ support package which allows an unambiguous choice
+of a mapping \chemgreek\ will make this choice automatically.  This means if
+you say
+\begin{sourcecode}
+  \usepackage{upgreek}
+  \usepackage{chemmacros}
+\end{sourcecode}
+then \chemmacros\ will use \pkg{upgreek}'s upright Greek letters.  If you
+have
+\begin{sourcecode}
+  \usepackage{upgreek}
+  \usepackage{chemmacros}
+  \usepackage{textgreek}
+\end{sourcecode}
+then no unambiguous choice is possible and you should choose a mapping
+yourself, for example:
+\begin{sourcecode}
+  \usepackage{upgreek}
+  \usepackage{chemmacros}
+  \usepackage{textgreek}
+  \chemsetup{greek=textgreek}
+\end{sourcecode}
+For further details on mappings please refer to \chemgreek's manual.
+
+\subsection{The \chemmodule*{lang} Module}\label{sec:lang-module}
+
+The \chemmodule{lang} module provides language support for \chemmacros.  It
+loads the package \pkg{translations}~\cite{pkg:translations}.
+
+\subsubsection{Information For Users}\label{sec:information-users}
+
+This module defines the following option:
+\begin{options}
+  \keychoice{language}{auto,\meta{language}}\Default{auto}
+    If set to \code{auto} \chemmacros\ will detect the language used by
+    \pkg{babel}~\cite{pkg:babel} or \pkg{polyglossia}~\cite{pkg:polyglossia}
+    automatically, the fallback translation is English and will be used if no 
+    translation for the actual language is available.  Any language known to
+    the \pkg{translations} package is a valid value for \meta{language}.
+\end{options}
+
+The language chosen via \option{language} is used for translation of certain
+strings in different places all over \chemmacros.  They are mentioned in the
+places when the corresponding function of \chemmacros\ is explained.
+
+Translation is done with the help of the \pkg{translations} package, available
+translation keys are listed in section~\vref{sec:avail-transl-keys}.
+
+\subsubsection{Available Translation Keys}\label{sec:avail-transl-keys}
+
+Table~\vref{tab:translation-keys} lists all predefined translations of the
+available keys.  \emph{Some of the translations have changed in
+  version~5.6\changedversion{5.6}.} The \chemmodule{lang} module doesn't
+provide the translations themselves -- they are provided by the corresponding
+modules.  A translation key is a unique string\footnote{That is, a string
+  using the definition for strings used for expl3, i.e., converted to a series
+  of category code~12 characters..} of characters.  Each key is used to
+identify a replacement text which depends on the current language or the
+language set through the \option{language} option.  For each key at least the
+English fallback translation is provided, for most also the German translation
+is provided.  For a few keys also other translations are provided.  If you
+find that a translation for your language is missing you can provide it in the
+preamble:
+\begin{commands}
+  % \command{DeclareTranslation}[\marg{language}\marg{key}\marg{translation}]
+  %   Defines a translation of key \meta{key} for the language \meta{language}.
+  %   No error will be raised if a translation of \meta{key} already exists.
+  %   This command can only be used in the preamble and is defined by the
+  %   \pkg{translations} package.
+  \command{DeclareChemTranslation}[\marg{key}\marg{language}\marg{translation}]
+    \sinceversion{5.6}A command which makes an abstraction from the
+    \pkg{translations} package.  It should be used in documents for adding
+    missing translations that are needed.  This command can only be used in
+    the preamble.
+  \command{DeclareChemTranslations}[\marg{key}\Marg{\meta{language} =
+    \meta{translation}}]
+    \sinceversion{5.6}A command rather meant for module writers but can be
+    used by document authors as well, of course.  It gets a csv list of
+    key\slash value pairs of translations.  This command can only be used in
+    the preamble.
+\end{commands}
+If you send me an email (see section~\vref{sec:sugg-bug-reports}) with the
+translations for your language I'll gladly add them to the next release of
+\chemmacros!
+
+\emph{Please do not use \pkg{translations}' \cs{DeclareTranslation} for
+  declaring translations.}
+
+\ForAllChemTranslationsDo{
+  \appto\chemtranslationtable{\texttt{#1} & #2 & \texttt{\detokenize{#3}} \\}
+}
+
+\begin{longtable}{lll}
+    \caption{Translation keys predefined by \chemmacros\ (except
+      \code{phase-aqi}, \code{phase-cd} and \code{phase-lc} which were defined
+      in this document).}
+    \label{tab:translation-keys} \\
+    \toprule
+    \bfseries key & \bfseries language & \bfseries translation \\
+    \midrule
+  \endfirsthead
+    \toprule
+    \bfseries key & \bfseries language & \bfseries translation \\
+    \midrule
+  \endhead
+    \bottomrule
+  \endlastfoot
+    \midrule
+    & & \hfill\emph{continues} \\
+  \endfoot
+  \chemtranslationtable
+\end{longtable}
+  
+\subsubsection{Information For Module Writers}
+
+In addition to the commands from section~\vref{sec:avail-transl-keys} the
+following macros are available:
+\begin{commands}
+  \expandable\explcommand{chemmacros_translate:n}[ \marg{translation key}]
+    Translates the given key to the language which is detected automatically
+    or given by the user.  Should be used in \chemmacros' macros instead of
+    \pkg{translations}' \cs*{GetTranslation}.
+  \explcommand{l_chemmacros_language_tl}
+    A token list variable that holds the language which is used by
+    \explcs{chemmacros_translate:n} for translation, \emph{after begin
+      document}.
+  \command{ChemTranslate}[\marg{translation key}]
+    A version of \explcs{chemmacros_translate:n} for those who prefer
+    traditional \LaTeXe\ programming over expl3.
+  \explcommand{chemmacros_declare_translation:nnn}[\marg{language}\marg{key}%
+    \marg{translation}]
+    The expl3 version of \cs{DeclareChemTranslation}.
+  \explcommand{chemmacros_declare_translations:nn}[\marg{key}\Marg{\meta{language}
+    = \meta{translation}}]
+    The expl3 version of \cs{DeclareChemTranslations}.
+\end{commands}
+
+\clearpage
+
+\part{Additional Modules}\label{part:additional-modules}
+
+\section{User Modules}
+\subsection{The \chemmodule*{all} \emph{pseudo}-module}\label{sec:all-module}
+
+The \chemmodule{all} module is a pseudo module: it doesn't define any
+functionality at all.  It does however load all other modules.  So you can say
+\begin{sourcecode}
+  \chemsetup{ modules = all }
+\end{sourcecode}
+to ensure that every module is available.  This \emph{will not} load personal
+modules!
+
+\subsection{The \chemmodule*{isotopes} Module}\label{sec:isotopes-module}
+
+The \chemmodule{isotope} module loads the \pkg{elements}
+package~\cite{pkg:elements}.  This module defines one user command:
+\begin{commands}
+  \command{isotope}[\sarg\marg{input}]
+    \meta{input} can either be the \emph{symbol} of an element or the
+    \emph{name} of an element.  Be aware that \emph{the name is language
+      dependent}, refer to the manual of the \pkg{elements} package for
+    details.  To be on the safe side use the element symbol.
+
+    \meta{input} can also be comma separated list:
+    \cs{isotope}\Marg{\meta{nuc},\meta{symbol}}.  If you leave \meta{nuc} out
+    then \cs{isotope} will display the most common isotope.  Otherwise
+    \meta{nuc} will be used.  If \meta{nuc} is an isotope unknown to the
+    \pkg{elements} package \cs{isotope} will write a warning to the log file.
+
+    The starred variant omits the element number.
+\end{commands}
+
+\begin{example}[side-by-side]
+  \isotope{C}
+  \isotope*{C}
+  \isotope{14,C}
+  \isotope*{14,C}
+\end{example}
+
+As input for the element symbol you can choose any of the elements known to
+the \pkg{elements} package.
+
+There are options which allow you to determine how the isotope is printed:
+\begin{options}
+  \keychoice{format}{super,side}\Module{isotopes}\Default{super}
+    Either print the isotope number as superscript or to the right of the
+    element symbol.
+  \keyval{side-connect}{input}\Module{isotopes}\Default{-}
+    Determine what is printed between the element symbol and the isotope
+    number if \keyis{format}{side}.
+\end{options}
+
+\begin{example}[side-by-side]
+  \isotope{C}
+  \chemsetup[isotopes]{format=side}
+  \isotope{C}
+  \chemsetup[isotopes]{side-connect=}
+  \isotope{C}
+\end{example}
+
+\subsection{The \chemmodule*{mechanisms} Module}\label{sec:mechanisms-module}
+
+The module \chemmodule{mechanisms} loads the package
+\pkg{amstext}~\cite{pkg:amstext}.  It provides one macro:
+
+\begin{commands}
+  \command{mech}[\oarg{type}]
+    Allows to specify the most common reaction mechanisms.
+\end{commands}
+\meta{type} can have one of the following values:
+\begin{commands}
+  \command{mech}
+    (empty, no opt. argument) nucleophilic substitution \mech
+  \command{mech}[\Oarg{1}]
+    unimolecular nucleophilic substitution \mech[1]
+  \command{mech}[\Oarg{2}]
+    bimolecular nucleophilic substitution \mech[2]
+  \command{mech}[\Oarg{se}]
+    electrophilic substitution \mech[se]
+  \command{mech}[\Oarg{1e}]
+    unimolecular electrophilic substitution \mech[1e]
+  \command{mech}[\Oarg{2e}]
+    bimolecular electrophilic substitution \mech[2e]
+  \command{mech}[\Oarg{ar}]
+    electrophilic aromatic substitution \mech[ar]
+  \command{mech}[\Oarg{e}]
+    elimination \mech[e]
+  \command{mech}[\Oarg{e1}]
+    unimolecular elimination \mech[e1]
+  \command{mech}[\Oarg{e2}]
+    bimolecular elimination \mech[e2]
+  \command{mech}[\Oarg{cb}]
+    unimolecular elimination \enquote{conjugated base}, \ie, via carbanion
+    \mech[cb]
+\end{commands}
+
+\subsection{The \chemmodule*{newman} Module}\label{sec:newman-module}
+The \chemmodule{newman} module provides a command for drawing Newman
+projections.  It loads the \chemmodule{tikz} module.
+\begin{commands}
+  \command{newman}[\oarg{options}\darg{angle}%
+    \Marg{\meta{1},\meta{2},\meta{3},\meta{4},\meta{5},\meta{6}}]
+    Create Newman projections.  This command uses \TikZ\ internally.
+    \meta{angle} rotates the back atoms counter clockwise with respect to the
+    front atoms and is an optional argument.  \meta{1} to \meta{6} are the
+    positions, the first three are the front atoms, the last three the back
+    atoms.
+\end{commands}
+
+\begin{example}
+  \newman{} \newman(170){}
+  \newman{1,2,3,4,5,6} \newman{1,2,3} \newman{,,,4,5,6}
+\end{example}
+
+Several options allow customization:
+\begin{options}
+  \keyval{angle}{angle}\Module{newman}\Default{0}
+    Default angle.
+  \keyval{scale}{factor}\Module{newman}\Default{1}
+    Scale the whole projection by factor \meta{factor}.
+  \keyval{ring}{tikz}\Module{newman}\Default
+    Customize the ring with \TikZ\ keys.
+  \keyval{atoms}{tikz}\Module{newman}\Default
+    Customize the nodes within which the atoms are set with \TikZ\ keys.
+  \keyval{back-atoms}{tikz}\Module{newman}\Default
+    Explicitly customize the nodes of the back atoms with \TikZ\ keys.
+\end{options}
+
+\begin{example}
+  \chemsetup[newman]{angle=45} \newman{}
+  \newman[scale=.75,ring={draw=blue,fill=blue!20}]{}
+\end{example}
+
+\begin{example}
+  \chemsetup[newman]{atoms={draw=red,fill=red!20,inner sep=2pt,rounded corners}}
+  \newman{1,2,3,4,5,6}
+\end{example}
+
+\begin{example}
+  \chemsetup[newman]{
+    atoms = {draw=red,fill=red!20,inner sep=2pt,rounded corners},
+    back-atoms = {draw=blue,fill=blue!20,inner sep=2pt,rounded corners}
+  }
+  \newman{1,2,3,4,5,6} \newman(170){1,2,3,4,5,6}
+\end{example}
+
+\subsection{The \chemmodule*{orbital} Module}\label{sec:orbital-module}
+The \chemmodule{orbital} module loads the \chemmodule{tikz} module.  It
+provides the following command to create orbitals:
+\begin{commands}
+  \command{orbital}[\oarg{options}\marg{type}]
+    Draw an orbital shape of type \meta{type}.  This command uses \TikZ\
+    internally.
+\end{commands}
+
+There are the following types available for \meta{type}:
+\begin{center}
+  \code{s} \quad
+  \code{p} \quad
+  \code{sp} \quad
+  \code{sp2} \quad
+  \code{sp3}
+\end{center}
+
+\begin{example}
+  \orbital{s} \orbital{p} \orbital{sp} \orbital{sp2} \orbital{sp3}
+\end{example}
+
+Depending on the type you have different options to modify the orbitals:
+\begin{options}
+  \keychoice{phase}{+,-}\Module{orbital}\Default{+}
+    changes the phase of the orbital (all types)
+  \keyval{scale}{factor}\Module{orbital}\Default{1}
+    changes the size of the orbital (all types)
+  \keyval{color}{color}\Module{orbital}\Default{black}
+    changes the color of the orbital (all types)
+  \keyval{angle}{angle}\Module{orbital}\Default{0}
+    rotates the orbitals with a p contribution counter clockwise (all types
+    except \code{s})
+  \keybool{half}\Module{orbital}\Default{false}
+    displays only half an orbital (only \code{p})
+\end{options}
+
+\begin{example}
+  \orbital{s} \orbital[phase=-]{s} 
+  \orbital{p} \orbital[phase=-]{p}
+  \orbital{sp3} \orbital[phase=-]{sp3}
+ 
+  \orbital[angle=0]{p} \orbital[color=red!50]{p}
+  \orbital[angle=135,scale=1.5]{p} \orbital[half]{p}
+\end{example}
+
+Additionally there are two options, with which the \TikZ\ behaviour can be
+changed.
+\begin{options}
+  \keybool{overlay}\Module{orbital}
+    The orbital \enquote{doesn't need space}; it is displayed with the \TikZ\
+    option \code{overlay}.
+  \keyval{opacity}{num}\Module{orbital}
+    The orbital becomes transparent; \meta{value} can have values between
+    \code{1} (fully opaque) to \code{0} (invisible).
+\end{options}
+\begin{example}
+  \vspace{7mm}
+  \chemsetup[orbital]{
+    overlay,
+    p/color = black!70
+  }
+  \setchemfig{bond offset=0pt}
+  \chemfig{
+    ?\orbital{p}
+    -[,1.3]{\orbital[phase=-]{p}}
+    -[:30,1.1]\orbital{p}
+    -[:150,.9]{\orbital[phase=-]{p}}
+    -[4,1.3]\orbital{p}
+    -[:-150,1.1]{\orbital[phase=-]{p}}?
+  }
+  \vspace{7mm}
+\end{example}
+
+\begin{example}
+  \vspace{7mm}
+  \setchemfig{bond offset = 0pt}
+  \chemsetup[orbital]{
+    overlay ,
+    opacity = .75 ,
+    p/scale = 1.6 ,
+    s/color = blue!50 ,
+    s/scale = 1.6
+  }
+  \chemfig{
+    \orbital{s}
+    -[:-20]{\orbital[scale=2]{p}}
+           {\orbital[half,angle=0]{p}}
+           {\orbital[angle=170,half]{p}}
+           {\orbital[angle=-150,half]{p}}
+    (-[:-150]\orbital{s})-\orbital{s}
+  }
+  \vspace{1cm}
+\end{example}
+
+\subsection{The \chemmodule*{polymers} Module}\label{sec:polymers-module}
+The\sinceversion{5.5} \chemmodule{polymers} module loads the
+\chemmodule{nomenclature} and the \chemmodule{tikz} modules.
+
+\subsubsection{Nomenclature}
+
+The \chemmodule{polymers} module defines a number of \ac{iupac} macros for
+usage inside \cs{iupac} which are used in polymer chemistry.
+
+\paragraph{Copolymers}
+\begin{commands}
+  \iupaccs[co]{copolymer}{unspecified copolymer.}
+  \iupaccs[stat]{statistical}{statistical copolymer.}
+  \iupaccs[ran]{random}{random copolymer.}
+  \iupaccs[alt]{alternating}{alternating copolymer.}
+  \iupaccs[per]{periodic}{periodic copolymer.}
+  \iupaccs{block}{block copolymer.}
+  \iupaccs{graft}{graft copolymer.}
+\end{commands}
+
+\paragraph{Non-linear (Co) Polymers and Polymer Assemblies}
+\begin{commands}
+  \iupaccs{blend}{The blend qualifier.}
+  \iupaccs{comb}{The comb qualifier.}
+  \iupaccs[compl]{complex}{The complex qualifier.}
+  \iupaccs[cyclo]{cyclic}{The cyclic qualifier.}
+  \iupaccs{branch}{The branch qualifier.}
+  \iupaccs[net]{network}{The network qualifier.}
+  \iupaccs[ipn]{ipnetwork}{The interpenetrating network qualifier.}
+  \iupaccs[sipn]{sipnetwork}{The semi-interpenetrating network qualifier.}
+  \iupaccs{star}{The star qualifier.}
+\end{commands}
+
+\subsubsection{Polymer Denotations in \pkg*{chemfig}'s Molecules}
+The \pkg{chemfig} manual proposes some code defining the macros
+\cs*{setpolymerdelim} and \cs*{makebraces} which make it possible to add
+delimiters to \pkg{chemfig} molecules.  The \chemmodule{polymers} module
+implements the following macro based on the same idea:
+\begin{commands}
+  \command{makepolymerdelims}[\oarg{options}\marg{height}\oarg{depth}\marg{opening
+    node}\marg{closing node}]
+    The value of \meta{depth} is the same as \meta{height} unless it is
+    specified explicitly.  \meta{opening node} and \meta{closing node} are the
+    names of \TikZ' nodes where the delimites are placed.
+\end{commands}
+\begin{options}
+  \keychoice{delimiters}{\Marg{\meta{left}\meta{right}}}\Module{polymers}\Default{[]}
+    This option demands two tokens as argument, the first being the opening
+    brace, the second the closing brace.  A dot (\code{.}) denotes an empty
+    delimiter.
+  \keyval{subscript}{subscript}\Module{polymers}\Default{\$n\$}
+    Subscript to the right delimiter.
+  \keyval{superscript}{superscript}\Module{polymers}
+    Superscript to the right delimiter.
+\end{options}
+
+\begin{example}
+  \setchemfig{atom sep=2em}
+  \chemfig{-[@{op,.75}]CH_2-CH(-[6]Cl)-[@{cl,0.25}]}
+  \makepolymerdelims{5pt}[27pt]{op}{cl}
+  \chemfig{-[@{op,.75}]CH_2-CH(-[6]Cl)-[@{cl,0.25}]}
+  \makepolymerdelims[delimiters=()]{5pt}[27pt]{op}{cl}
+\end{example}
+
+\subsection{The \chemmodule*{reactions} Module}\label{sec:reactions-module}
+The \chemmodule{reactions} module loads the \chemmodule{chemformula} module
+and the \pkg{mathtools} package~\cite{pkg:mathtools}.
+
+\subsubsection{Predefined Environments}
+
+You can use these environments for numbered\ldots
+\begin{environments}
+  \environment{reaction}
+    A single reaction where \chemformula\ code is placed directly in the
+    environment body.  A wrapper around the \env*{equation} environment.  The
+    environment body is parsed with \cs{ch} or \cs{ce} depending on the value
+    of the \option{formula} option, see
+    section~\vref{sec:chemformula-module}.
+  \environment{reactions}
+    Several aligned reactions.  A wrapper around \pkg{amsmath}'s \env*{align}
+    environment.  The environment body is parsed with \cs{ch} or \cs{ce}
+    depending on the value of the \option{formula} option, see
+    section~\vref{sec:chemformula-module}.
+\end{environments}
+
+\ldots and their starred versions for unnumbered reactions.
+\begin{environments}
+  \environment{reaction*}
+    A wrapper around the \env*{equation*} environment.  The environment body
+    is parsed with \cs{ch} or \cs{ce} depending on the value of the
+    \option{formula} option, see section~\vref{sec:chemformula-module}.
+  \environment{reactions*}
+    A wrapper around \pkg{amsmath}'s \env*{align*} environment.  The
+    environment body is parsed with \cs{ch} or \cs{ce} depending on the value
+    of the \option{formula} option, see
+    section~\vref{sec:chemformula-module}.
+\end{environments}
+
+With those environments you can create (un)numbered reaction equations similar
+to mathematical equations.
+
+Theses environments use the \env*{equation}/\env*{equation*} environments or
+the \env*{align}/\env*{align*} environments, respectively, to display the
+reactions.
+
+\begin{example}
+  Reaction with counter:
+  \begin{reaction}
+    A -> B
+  \end{reaction}
+\end{example}
+
+\begin{example}
+  Reaction without counter:
+  \begin{reaction*}
+    C -> D
+  \end{reaction*}
+\end{example}
+
+\begin{example}
+  Several aligned reactions with counter:
+  \begin{reactions}
+    A     &-> B + C \\
+    D + E &-> F
+  \end{reactions}
+\end{example}
+
+\begin{example}
+  Several aligned reactions without counter:
+  \begin{reactions*}
+    G     &-> H + I \\
+    J + K &-> L
+  \end{reactions*}
+\end{example}
+
+If you want to change the layout of the counter tags, you can use
+\begin{commands}
+  \command*{renewtagform}[\marg{tagname}\oarg{format}\marg{left
+    delimiter}\marg{right delimiter}]
+    Provided by the \pkg{mathtools} package.
+\end{commands}
+or use the following options:
+\begin{options}
+  \keyval{tag-open}{left delimiter}\Module{reactions}\Default{\{}
+    \sinceversion{5.6}The left delimiter.
+  \keyval{tag-close}{right delimiter}\Module{reactions}\Default{\}}
+    \sinceversion{5.6}The right delimiter.
+  \keyval{before-tag}{format}\Module{reactions}\Default
+    \sinceversion{5.6}Code inserted before the tags.
+\end{options}
+
+\begin{example}
+  \chemsetup[reactions]{
+    before-tag = R \textbf ,
+    tag-open = [ ,
+    tag-close = ]
+  }
+  \begin{reaction}
+    H2O + CO2 <<=> H2CO3
+  \end{reaction}
+\end{example}
+
+The use of \AmS math's \cs{intertext} is possible:
+\begin{example}
+  \begin{reactions}
+    A + 2 B &-> 3 C + D "\label{rxn:test}"
+    \intertext{Some text in between aligned reactions}
+    3 E + F &<=> G + 1/2 H
+  \end{reactions}
+  See reaction~\ref{rxn:test}.
+\end{example}
+
+If\sinceversion{5.6} you are using either \pkg{cleveref} or \pkg{fancyref} the
+\env{reaction} counter is supported already.  For \pkg{fancyref} use the
+prefix \code{rct}.
+
+\subsubsection{Own Reactions}
+You can create new types of reactions with the command:
+\begin{commands}
+  \command{NewChemReaction}[\marg{name}\oarg{number of arguments}\marg{math name}]
+    \meta{name} will be the name of the new chem environment. \meta{math name} is
+    the underlying math environment.  Gives an error if \meta{name} already
+    exists.
+  \command{RenewChemReaction}[\marg{name}\oarg{number of arguments}\marg{math name}]
+    \meta{name} is the name of the renewed chem environment. \meta{math name} is
+    the underlying math environment.  Gives an error if \meta{name} does not exist.
+  \command{DeclareChemReaction}[\marg{name}\oarg{number of arguments}\marg{math name}]
+    \meta{name} will be the name of the chem environment. \meta{math name} is
+    the underlying math environment.
+  \command{ProvideChemReaction}[\marg{name}\oarg{number of arguments}\marg{math name}]
+    \meta{name} will be the name of the new chem environment. \meta{math name} is
+    the underlying math environment.  The new environment is only defined if
+    it doesn't exist, yet.
+\end{commands}
+
+\begin{sourcecode}
+  \NewChemReaction{reaction}  {equation}
+  \NewChemReaction{reaction*} {equation*}
+  \NewChemReaction{reactions} {align}
+  \NewChemReaction{reactions*}{align*}
+\end{sourcecode}
+
+Let's suppose, you'd like to have the alignment behaviour of the \env{alignat}
+environment for \chemformula\ reactions.  You could do the following:
+
+\begin{sourcecode}
+  \NewChemReaction{reactionsat}[1]{alignat}
+\end{sourcecode}
+
+With this the \env{reactionsat} environment is defined.
+\begin{example}
+  \NewChemReaction{reactionsat}[1]{alignat}
+  \NewChemReaction{reactionsat*}[1]{alignat*}
+  \begin{reactionsat}{3}
+    A     &-> B     &&-> C     &&-> D \\
+    aaaaa &-> bbbbb &&-> ccccc &&-> ddddd
+  \end{reactionsat}
+  \begin{reactionsat*}{2}
+    A     &-> B     & C            &-> D  \\
+    aaaaa &-> bbbbb &\quad{} ccccc &-> ddddd
+  \end{reactionsat*}
+\end{example}
+
+\subsubsection{List of Reactions}
+
+The \chemmodule{reactions} module also provides a command to display a list of
+the reactions created with the \env{reaction} environment.
+\begin{commands}
+  \command{listofreactions}
+    Print a list of reactions.
+\end{commands}
+\begin{example}
+  \listofreactions
+\end{example}
+
+The output of this list can be modified by two options:
+\begin{options}
+  \keyval{list-name}{name of the
+    list}\Module{reactions}\Default{\cs*{ChemTranslate}\Marg{{list-of-reactions}}}
+    Let's you set the name of the list manually.  The default name is language
+    dependent, see section~\vref{sec:lang-module}.
+  \keyval{list-entry}{prefix to each
+    entry}\Module{reactions}\Default{\cs*{ChemTranslate}\Marg{reaction}}
+    Let's you set a prefix to each list entry.  The default name is language
+    dependent, see section~\vref{sec:lang-module}.
+  \keyval{list-heading-cmd}{code}\Module{reactions}\Default{\cs*{section}\sarg\Marg{\#1}}
+    The\sinceversion{5.2} macro that is called at the beginning of the list.
+    Inside of \meta{code} \code{\#1} refers to the actual heading of the list.
+    The default setting is not entirely true: if a macro \cs*{chapter} is
+    defined \code{\cs*{chapter}\sarg\Marg{\#1}} is used.
+  \keybool{tocbasic}\Module{reactions}\Default{false}
+    \sinceversion{5.6}If you use a \KOMAScript\ class \emph{or} if you load
+    the \pkg{tocbasic} package \emph{or} if you set this option to \code{true}
+    the list of reactions will be set up using the \pkg{tocbasic} package.
+    This \emph{disables} the \option{list-heading-cmd} option.  For a
+    \KOMAScript\ class this means that the list of reactions obeys
+    \KOMAScript's \option*{listof} option.
+\end{options}
+Instead of using the option \option{list-name} you also could redefine
+\cs{reactionlistname}.
+
+The list lists all reactions with a number and disregards reactions without
+number.  All reaction environments without star have an optional argument
+which let's you add a description (or caption) for the entry in the list.
+\begin{example}
+  \begin{reaction}[Autoprotolyse]
+    2 H2O <<=> H3O+ + OH-
+  \end{reaction}
+\end{example}
+
+If you use the \env{reactions} environment this will not work, though.  In
+this case you can use
+\begin{commands}
+  \command{AddRxnDesc}[\marg{description}]
+    Add a description to a reaction.
+\end{commands}
+
+\begin{example}
+  \begin{reactions}
+    "\chlewis{0.}{Cl}" + CH4  &
+      -> HCl + "\chlewis{180.}{C}" H3 \AddRxnDesc{first~step~of~chain} \\
+    "\chlewis{180.}{C}" H3 + Cl2 &
+      -> CH3Cl + "\chlewis{0.}{Cl}" \AddRxnDesc{second~step~of~chain}
+  \end{reactions}
+\end{example}
+
+\subsection{The \chemmodule*{redox} Module}\label{sec:redox-module}
+
+The \chemmodule{redox} module loads the modules \chemmodule{tikz} and
+\chemmodule{xfrac}. It also loads the packages
+\pkg{mathtools}~\cite{pkg:mathtools} and \pkg{relsize}~\cite{pkg:relsize}.
+
+\subsubsection{Oxidation Numbers}\label{sec:oxidation-numbers}
+
+Regarding the typesetting of oxidation numbers
+\citetitle{iupac:greenbook}~\cite{iupac:greenbook} says the following:
+\begin{cnltxquote}[{\cite[][p.\,50]{iupac:greenbook}}]
+  Oxidation numbers are denoted by positive or negative Roman numerals or by
+  zero \textelp{}
+
+  \textit{Examples}\quad \ox{7,Mn}, \ox[pos=side]{7,manganese}, \ox{-2,O},
+  \ox{0,Ni}
+\end{cnltxquote}
+
+The following command is provided to set oxidation numbers:
+\begin{commands}
+  \command{ox}[\sarg\oarg{options}\Marg{\meta{number},\meta{atom}}]
+    Places \meta{number} as right superscript to \meta{atom}; \meta{number}
+    has to be a (rational) number!  \meta{atom} is treated as a \chemformula\
+    formula, like it would be in \cs{chcpd} (this depends on the setting of
+    the \option{formula} option, see~\vref{sec:chemformula-module}).
+\end{commands}
+
+\begin{example}
+  \ox{+1,Na}, \ox{2,Ca}, \ox{-2,S}, \ox{-1,F}
+\end{example}
+
+There are a number of options that can be used to modify the typeset result:
+\begin{options}
+  \keybool{parse}\Module{redox}\Default{true}
+    When \code{false} an arbitrary entry can be used for \code{<number>}.
+  \keybool{roman}\Module{redox}\Default{false}
+    Switches from roman to arabic numbers.
+  \keychoice{pos}{top,super,side}\Module{redox}\Default{super}
+    \code{top} places \meta{number} above \meta{atom}, \code{super} to the
+    upper right as superscript and \code{side} to the right and inside
+    brackets.  Both \code{super} and \code{side} follow \ac{iupac}
+    recommendation, \code{top} does not!
+  \keybool{explicit-sign}\Module{redox}\Default{false}
+    Shows the $+$ for positiv numbers and the $\pm$ for $0$.
+  \keybool{explizit-zero-sign}\Module{redox}\Default{true}
+    Only\sinceversion{5.4} if both \option{explicit-sign} and
+    \option{explicit-zero-sign} are set to \code{true} $\pm0$ will be
+    printed.
+  \keychoice{decimal-marker}{comma,point}\Module{redox}\Default{point}
+    Choice for the decimal marker for formal oxidation numbers like \ox{1.2,X}.
+  \keychoice{align}{center,right}\Module{redox}\Default{center}
+    Center the oxidation number relative to the atom or right-align it.
+  \keyval{side-connect}{code}\Module{redox}\Default{\cs*{,}}
+    Code that is inserted between atom and oxidation number if
+    \keyis{pos}{side} is used.
+  \keyval{text-frac}{cs}\Module{redox}\Default{\cs{chemfrac}\Oarg{text}\Marg{\#1}\Marg{\#2}}
+    The fraction macro that is used for fractions if \keyis{pos}{side} is
+    used.  \meta{cs} must be a macro that takes two mandatory arguments, the
+    first for the numerator and the second for the denominator.
+  \keyval{super-frac}{cs}\Module{redox}\Default{\cs{chemfrac}\Oarg{superscript}%
+    \Marg{\#1}\Marg{\#2}}
+    The fraction macro that is used for fractions if \keyis{pos}{top} or
+    \keyis{pos}{super} is used.  \meta{cs} must be a macro that takes two
+    mandatory arguments, the first for the numerator and the second for the
+    denominator.
+\end{options}
+
+\begin{example}[side-by-side]
+  \ox[roman=false]{2,Ca} \ox{2,Ca} \\
+  \ox[pos=top]{3,Fe}-Oxide \\
+  \ox[pos=side]{3,Fe}-Oxide \\
+  \ox[parse=false]{?,Mn} \\
+  \ox[pos=top,align=right]{2,Ca}
+\end{example}
+
+The \keyis{pos}{top} variant also can be set with the shortcut \cs{ox}\sarg:
+\begin{example}[side-by-side]
+  \ox{3,Fe} \ox*{3,Fe}
+\end{example}
+
+Using the \option{explicit-sign} option will always show the sign of the
+oxidation number:
+\begin{example}
+  \chemsetup[redox]{explicit-sign = true}
+  \ox{+1,Na}, \ox{2,Ca}, \ox{-2,S}, \ch{"\ox{0,F}" {}2}
+\end{example}
+
+\begin{example}
+  \chemsetup[redox]{pos=top}
+  Compare \ox{-1,O2^2-} to \ch{"\ox{-1,O}" {}2^2-}
+\end{example}
+
+Sometimes one might want to use formal oxidation numbers like \num{.5} or
+\chemfrac{1}{3}:
+\begin{example}[side-by-side]
+  \chemsetup[redox]{pos=top}
+  \ox{.5,Br2}
+  \ch{"\ox{1/3,I}" {}3+}
+
+  \chemsetup[redox]{pos=side}
+  \ox{1/3,I3+}
+\end{example}
+
+The fraction is displayed with the help of the \pkg{xfrac}
+package~\cite{bnd:l3packages}.  For more details on how \chemmacros\ uses it
+read section~\vref{sec:xfrac-module}.
+
+\subsubsection{Redox Reactions}\label{sec:redox-reactions}
+
+\chemmacros\ provides two commands to visualize the transfer of electrons in
+redox reactions.  Both commands are using \TikZ.
+\begin{commands}
+  \command{OX}[\Marg{\meta{name},\meta{atom}}]
+    Label \meta{atom} with the label \meta{name}.
+  \command{redox}[\Darg{\meta{name1},\meta{name2}}\oarg{tikz}\oarg{num}\marg{text}]
+    Connect two \meta{atom}s previously labelled with \cs{OX}.  Only the first
+    argument \Darg{\meta{name1},\meta{name2}} is required, the others are all
+    optional.
+\end{commands}
+
+\cs{OX} places \meta{atom} into a node, which is named with \meta{name}.  If
+you have set two \cs{OX}, they can be connected with a line using \cs{redox}.
+To do so the names of the two nodes that are to be connected are written in
+the round braces.  Since \cs{redox} draws a \code{tikzpicture} with options
+\code{remember picture,overlay}, the document needs to be \emph{compiled at
+  least two times}.
+
+\begin{example}
+  \vspace{7mm}
+  \OX{a,Na} $\rightarrow$ \OX{b,Na}\pch\redox(a,b){oxidation}
+\end{example}
+
+This line can be customized using \TikZ\ keys in \oarg{tikz}:
+\begin{example}
+  \vspace{7mm}
+  \OX{a,Na} $\rightarrow$ \OX{b,Na}\pch\redox(a,b)[->,red]{ox}
+\end{example}
+
+With the argument \oarg{num} the length of the vertical parts of the line can
+be adjusted.  The default length is \code{.6em}.  This length is multiplied
+with \meta{num}.  If you use a negative value the line is placed \emph{below}
+the text.
+\begin{example}
+  \vspace{7mm}
+  \OX{a,Na} $\rightarrow$ \OX{b,Na}\pch
+  \redox(a,b)[->,red]{ox}
+  \redox(a,b)[<-,blue][-1]{red}
+  \vspace{7mm}
+\end{example}
+
+The default length of the vertical lines can be customized with the option
+\begin{options}
+  \keyval{dist}{dim}\Module{redox}\Default{.6em}
+    A \TeX\ dimension.
+\end{options}
+
+\begin{example}
+  \vspace{7mm}
+  \chemsetup{redox/dist=1em}
+  \OX{a,Na} $\rightarrow$ \OX{b,Na}\pch\redox(a,b)[->,red]{ox}
+\end{example}
+
+\begin{options}
+  \keyval{sep}{dim}\Module{redox}\Default{.2em}
+    The option can be used to change the distance between the atom and the
+    beginning of the line.
+\end{options}
+
+\begin{example}
+  \vspace{7mm}
+  \chemsetup{redox/sep=.5em}
+  \OX{a,Na} $\rightarrow$ \OX{b,Na}\pch\redox(a,b)[->,red]{ox}
+\end{example}
+
+\paragraph{Examples}
+\begin{example}
+  \vspace{7mm}
+  \ch{
+    2 "\OX{o1,Na}" + "\OX{r1,Cl}" {}2
+    ->
+    2 "\OX{o2,Na}" {}+ + 2 "\OX{r2,Cl}" {}-
+  }
+  \redox(o1,o2){\small OX: $- 2\el$}
+  \redox(r1,r2)[][-1]{\small RED: $+ 2\el$}
+  \vspace{7mm}
+\end{example}
+
+\begin{example}
+  \vspace{7mm}
+  \ch{
+    2 "\OX{o1,\ox*{0,Na}}" + "\OX{r1,\ox*{0,Cl}}" {}2
+    ->
+    2 "\OX{o2,\ox*{+1,Na}}" {}+ + 2 "\OX{r2,\ox*{-1,Cl}}" {}-
+  }
+  \redox(o1,o2){\small OX: $- 2\el$}
+  \redox(r1,r2)[][-1]{\small RED: $+ 2\el$}
+  \vspace{7mm}
+\end{example}
+
+\begin{example}
+  \vspace{14mm}
+  \ch{
+    2 "\OX{o1,\ox*{0,Na}}" + "\OX{r1,\ox*{0,Cl}}" {}2
+    ->
+    2 "\OX{o2,\ox*{+1,Na}}" {}+ + 2 "\OX{r2,\ox*{-1,Cl}}" {}-
+  }
+  \redox(o1,o2)[draw=red,->][3.33]{\small OX: $- 2\el$}
+  \redox(r1,r2)[draw=blue,->]{\small RED: $+ 2\el$}
+\end{example}
+
+\begin{example}
+  \vspace{7mm}
+  \ch{
+    2 "\OX{o1,\ox*{0,Na}}" + "\OX{r1,\ox*{0,Cl}}" {}2
+    -> 2 "\OX{o2,\ox*{+1,Na}}" {}+ + 2 "\OX{r2,\ox*{-1,Cl}}" {}-
+  }
+  \redox(o1,o2)[green,-stealth]{\small OX}
+  \redox(r1,r2)[purple,-stealth][-1]{\small RED}
+  \vspace{7mm}
+\end{example}
+
+\subsection{The \chemmodule*{scheme} Module}\label{sec:scheme-module}
+
+The \chemmodule{scheme} module loads the \pkg{chemnum}
+package~\cite{pkg:chemnum} and defines a floating environment
+\showenv{scheme}.  That is, it \emph{only} defines this float if no
+environment \env{scheme} exists at the end of the preamble.  The module checks
+for different available float defining methods, in \emph{this} order:
+\begin{itemize}
+  \item If the current class is a \KOMAScript\ class \cs*{DeclareNewTOC} will
+    be used.
+  \item If the current class is \cls{memoir}, \cls{memoir}'s methods are used.
+  \item If the package \pkg{tocbasic} has been loaded \cs*{DeclareNewTOC} will
+    be used.
+  \item If the package \pkg{newfloat} has been loaded
+    \cs*{DeclareFloatingEnvironment} will be used.
+  \item \sinceversion{5.1}If the package \pkg{floatrow} has been loaded its
+    method will be used.
+  \item If the package \pkg{float} has been loaded its method will be used.
+  \item If neither of the above the \enquote{manual} method is used.  This
+    means the environment is defined the same way like \env*{figure} is
+    defined in the \cls*{article} class or the \cls*{book} class, depending if
+    \cs*{chapter} is defined or not.
+\end{itemize}
+
+The list name and the caption name both are translated to the language
+specified according to the \option{lang} option and the provided translations,
+see section~\vref{sec:lang-module} for details. If you want to manually change
+them then redefine these macros after begin document:
+\begin{commands}
+  \command{listschemename}
+    The name of the list of schemes.
+  \command{schemename}
+    The name used in captions.
+\end{commands}
+The list of schemes is printed as expected with
+\begin{commands}
+  \command{listofschemes}
+\end{commands}
+
+If\sinceversion{5.6} you are using either \pkg{cleveref} or \pkg{fancyref} the
+\env{scheme} environment (or rather its captions) are supported already.  For
+\pkg{fancyref} use the prefix \code{sch}.
+
+\subsection{The \chemmodule*{spectroscopy} Module}\label{sec:spectroscopy-module}
+
+The \chemmodule{spectroscopy} module loads the \chemmodule{chemformula} module
+and the \pkg{siunitx} package~\cite{pkg:siunitx}.
+
+\subsubsection{The \cs*{NMR} Command}
+
+When you're trying to find out if a compound is the one you think it is often
+NMR spectroscopy is used.  The experimental data are typeset similar to this:
+\begin{center}
+  \NMR(400)[CDCl3] = \num{1.59}
+\end{center}
+The \chemmodule{spectroscopy} module provides a command which simplifies the
+input.
+
+\begin{commands}
+  \command{NMR}[\sarg\Marg{\meta{num},\meta{element}}%
+    \Darg{\meta{num},\meta{unit}}\oarg{solvent}]
+    Typeset nuclear magnetic resonance data. \meta{num} is a valid
+    \pkg{siunitx} number input, \meta{unit} is a valid \pkg{siunitx} unit
+    input.  \meta{solvent} is any valid \chemformula\ input as in \cs{chcpd}
+    (this depends on the setting of the \option{formula} option,
+    see~\vref{sec:chemformula-module}).
+\end{commands}
+
+\emph{All} Argument are optional! Without arguments we get:
+\begin{example}[side-by-side]
+  \NMR \par
+  \NMR*
+\end{example}
+
+The first argument specifies the kind of NMR:
+\begin{example}[side-by-side]
+  \NMR{13,C}
+\end{example}
+
+The second argument sets the frequency (in \si{\mega\hertz}):
+\begin{example}[side-by-side]
+  \NMR(400)
+\end{example}
+You can choose another unit:
+\begin{example}[side-by-side]
+  \NMR(4e8,\hertz)
+\end{example}
+Please note that the setup of \pkg{siunitx} also affects this command:
+\begin{example}[side-by-side]
+  \sisetup{exponent-product=\cdot}
+  \NMR(4e8,\hertz)
+\end{example}
+
+The third argument specifies the solvent:
+\begin{example}[side-by-side]
+  \NMR[CDCl3]
+\end{example}
+
+\subsubsection{Short Cuts}
+
+It is possible to define short cut commands for specific nuclei.
+\begin{commands}
+  \command{NewChemNMR}[\marg{cs}\Marg{\meta{num},\meta{atom}}]
+    Define a new shortcut macro for typesetting a certain type of magnetic
+    resonence data.  Gives an error if \meta{cs} already exists.
+  \command{DeclareChemNMR}[\marg{cs}\Marg{\meta{num},\meta{atom}}]
+    Define a new shortcut macro for typesetting a certain type of magnetic
+    resonence data.  Overwrites an existing macro.
+  \command{RenewChemNMR}[\marg{cs}\Marg{\meta{num},\meta{atom}}]
+    Redefine an existing shortcut macro for typesetting a certain type of
+    magnetic resonence data.  Gives an error if \meta{cs} doesn't exist.
+  \command{ProvideChemNMR}[\marg{cs}\Marg{\meta{num},\meta{atom}}]
+    Define a new shortcut macro for typesetting a certain type of magnetic
+    resonence data.  \meta{cs} is only defined if it doesn't exist, yet.
+\end{commands}
+
+This defines a command with the same arguments as \cs{NMR} \emph{except} for
+\Marg{\meta{num},\meta{atom}}:
+\begin{example}[side-by-side]
+  \NewChemNMR\HNMR{1,H}%
+  \NewChemNMR\CNMR{13,C}%
+  \CNMR*(100) \par
+  \HNMR*(400)
+\end{example}
+
+\subsubsection{An Environment to Typeset Experimental Data}
+
+The \chemmodule{spectroscopy} module provides an environment to ease the input
+of experimental data.
+\begin{environments}
+  \environment{experimental}
+    Environment for the output of experimental data.  Inside the environment
+    the following commands are defined.
+\end{environments}
+\begin{commands}
+  \command{data}[\marg{type}\oarg{specification}]
+    Type of data, \eg\ IR, MS\ldots\  The optional argument takes further
+    specifications which are output in parentheses.
+  \command{data}[\sarg\marg{type}\oarg{specification}]
+    Like \cs{data} but changes the \code{=} into a \code{:}, given that
+    \keyis{use-equal}{true} is used.
+  \command{NMR}[\Marg{\meta{num},\meta{elem}\oarg{coupling
+      core}}\Darg{\meta{num},\meta{unit}}\oarg{solvent}]
+    This command gets an additional argument:
+    \cs{NMR}\Marg{13,C[\textasciicircum 1H]} \NMR{13,C[^1H]}
+  \command{J}[\Darg{\meta{bonds};\meta{nuclei}}\oarg{unit}\marg{list of nums}]
+    Coupling constant, values are input separated by \code{;} (NMR).  The
+    arguments \Darg{\meta{bonds};\meta{nuclei}} and \oarg{unit} are optional
+    and enable further specifications of the coupling.
+  \command{\#}[\marg{num}]
+    Number of nuclei (NMR).
+  \command{pos}[\marg{num}]
+    Position of nuclues (NMR).
+  \command{val}[\marg{num}]
+    A number, an alias of \pkg{siunitx}' \cs*{num}\marg{num}.
+  \command{val}[\Marg{\meta{num1}--\meta{num2}}]
+    An alias of \pkg{siunitx}' \cs*{numrange}\marg{num1}\marg{num2}.
+\end{commands}
+
+\begin{example}
+  \begin{experimental}
+    \data{type1} Data.
+    \data{type2}[specifications] More data.
+    \data*{type3} Even more data.
+  \end{experimental}
+\end{example}
+
+\paragraph{Customization}\label{sec:experimental-customization}
+
+The output of the environment and of the NMR commands can be customized be a
+number of options.  For historical reasons they all belong to the module
+\module{nmr}.
+\begin{options}
+  \keyval{unit}{unit}\Module{spectroscopy}\Default{\cs*{mega}\cs*{hertz}}
+    The used default unit.
+  \keychoice{nucleus}{\Marg{\meta{num},\meta{atom}}}\Module{spectroscopy}\Default{\Marg{1,H}}
+    The used default nucleus.
+  \keyval{connector}{code}\Module{spectroscopy}\Default{-}
+    Places \meta{code} between the nucleus and the method.
+  \keyval{method}{code}\Module{spectroscopy}\Default{NMR}
+    The measuring method.
+  \keyval{format}{commands}\Module{spectroscopy}\Default
+    For example \cs*{bfseries}.
+  \keyval{nmr-base-format}{commands}\Module{spectroscopy}\Default
+    \sinceversion{5.8}Formatting instructions for the NMR base.
+  \keychoice{pos-number}{side,sub,super}\Module{spectroscopy}\Default{side}
+    Position of the number next to the atom.
+  \keyval{coupling-symbol}{code}\Module{spectroscopy}\Default{J}
+    The symbol used for the coupling constant.
+  \keyval{coupling-unit}{unit}\Module{spectroscopy}\Default{\cs*{hertz}}
+    A \pkg{siunitx} unit.
+  \keychoice{coupling-pos}{side,sub}\Module{spectroscopy}\Default{side}
+    Placement of the coupling nuclei next to the symbol $J$ (or rather the
+    symbol specified with option \option{coupling-symbol}).
+  \keyval{coupling-nuclei-pre}{code}\Module{spectroscopy}\Default{(}
+    Code inserted before the coupling nuclei when \keyis{coupling-pos}{side}.
+  \keyval{coupling-nuclei-post}{code}\Module{spectroscopy}\Default{)}
+    Code inserted after the coupling nuclei when \keyis{coupling-pos}{side}.
+  \keyval{coupling-bonds-pre}{code}\Module{spectroscopy}\Default
+    Code inserted before the coupling bonds.
+  \keyval{coupling-bonds-post}{code}\Module{spectroscopy}\Default{\cs*{!}}
+    Code inserted after the coupling bonds.
+  \keyval{coupling-pos-cs}{cs}\Module{spectroscopy}\Default{\cs*{@firstofone}}
+    Set the macro that prints the number set with the \cs{pos} macro.  This
+    needs to be a command with one mandatory argument.
+  \keyval{atom-number-cs}{cs}\Module{spectroscopy}\Default{\cs*{@firstofone}}
+    Set the macro that prints the number set with the \cs{\#} macro.  This
+    needs to be a command with one mandatory argument.
+  \keyval{atom-number-space}{dim}\Module{spectroscopy}\Default{.16667em}
+    Horizontal\sinceversion{5.3} space inserted between number and atom
+    (printed by \cs{\#}).
+  \keybool{parse}\Module{spectroscopy}\Default{true}
+    Treat the solvent as \chemformula\ formula (this depends on the setting of
+    the \option{formula} option, see~\vref{sec:chemformula-module}) or not.
+  \keyval{delta}{tokens}\Module{spectroscopy}\Default
+    The \meta{tokens} are added after $\delta$.
+  \keybool{list}\Module{spectroscopy}\Default{false}
+    The environment \env{nmr}[<optionen>]{} is formatted as a list
+  \keyval{list-setup}{setup}\Module{spectroscopy}
+    Setup of the list. See below for the default settings.
+  \keybool{use-equal}\Module{spectroscopy}\Default{false}
+    Add egual sign after \cs{NMR} and \cs{data}.
+\end{options}
+
+The default setup of the list:
+\begin{sourcecode}
+  \topsep\z@skip \partopsep\z@skip 
+  \itemsep\z@ \parsep\z@ \itemindent\z@
+  \leftmargin\z@
+\end{sourcecode}
+
+\begin{example}
+  \begin{experimental}[format=\bfseries]
+    \data{type1} Data.
+    \data{type2}[specifications] More data.
+    \data*{type3} Even more data.
+  \end{experimental}
+\end{example}
+
+The command \cs{NMR} and all commands defined through \cs{NewChemNMR}
+can be used like \cs{data} for the NMR data.
+
+\begin{example}
+  \begin{experimental}[format=\bfseries,use-equal]
+    \data{type1} Data.
+    \data{type2}[specifications] More data.
+    \NMR Even more data.
+  \end{experimental}
+\end{example}
+
+\paragraph{An Example}
+The code below is shown with different specifications for \meta{options}.
+Of course options can also be chosen with \cs{chemsetup}.
+
+\begin{sourcecode}
+  \sisetup{separate-uncertainty,per-mode=symbol,detect-all,range-phrase=--}
+  \begin{experimental}[<optionen>]
+    \data*{yield} \SI{17}{\milli\gram} yellow needles (\SI{0.04}{\milli\mole},
+      \SI{13}{\percent}).
+    %
+    \data{mp.} \SI{277}{\celsius} (DSC).
+    %
+    \NMR(600)[CDCl3] \val{2.01} (s, \#{24}, \pos{5}), \val{2.31} (s, \#{12},
+    \pos{1}), \val{6.72--6.74} (m, \#{2}, \pos{11}), \val{6.82} (s, \#{8},
+    \pos{3}), \val{7.05--7.07} (m, \#{2}, \pos{12}), \val{7.39--7.41} (m, \#{4},
+    \pos{9}), \val{7.48--7.49} (m, \#{4}, \pos{8}).
+    %
+    \NMR{13,C}(150)[CDCl3] \val{21.2} ($+$, \#{4}, \pos{1}), \val{23.4} ($+$,
+    \#{8}, \pos{5}), \val{126.0} ($+$, \#{4}, \pos{9}), \val{128.2} ($+$, \#{8},
+    \pos{3}), \val{130.8} ($+$, \#{2}, \pos{12}), \val{133.6} ($+$, \#{2},
+    \pos{11}), \val{137.0} ($+$, \#{4}, \pos{8}), \val{138.6} (q, \#{4},
+    \pos{2}), \val{140.6} (q, \#{2}, \pos{10}), \val{140.8} (q, \#{8}, \pos{4}),
+    \val{141.8} (q, \#{4}, \pos{6}), \val{145.6} (q, \#{2}, \pos{7}).
+    %
+    \data{MS}[DCP, EI, \SI{60}{\electronvolt}] \val{703} (2, \ch{M+}), \val{582}
+    (1), \val{462} (1), \val{249} (13), \val{120} (41), \val{105} (100).
+    %
+    \data{MS}[\ch{MeOH + H2O + KI}, ESI, \SI{10}{\electronvolt}] \val{720} (100,
+    \ch{M+ + OH-}), \val{368} (\ch{M+ + 2 OH-}).
+    %
+    \data{IR}[KBr] \val{3443} (w), \val{3061} (w), \val{2957} (m), \val{2918}
+    (m), \val{2856} (w), \val{2729} (w), \val{1725} (w), \val{1606} (s),
+    \val{1592} (s), \val{1545} (w), \val{1446} (m), \val{1421} (m), \val{1402}
+    (m), \val{1357} (w), \val{1278} (w), \val{1238} (s), \val{1214} (s),
+    \val{1172} (s), \val{1154} (m), \val{1101} (w), \val{1030} (w), \val{979}
+    (m), \val{874} (m), \val{846} (s), \val{818} (w), \val{798} (m), \val{744}
+    (w), \val{724} (m), \val{663} (w), \val{586} (w), \val{562} (w), \val{515}
+    (w).
+    %
+    \data*{UV-Vis} \SI{386}{\nano\metre} ($\varepsilon = \val{65984}$),
+    \SI{406}{\nano\metre} ($\varepsilon = \val{65378}$).
+    %
+    \data*{quantum yield} $\Phi = \val{0.74+-0.1}$\,.
+  \end{experimental}
+\end{sourcecode}
+
+\paragraph{Nearly Standard}
+Output with these options:
+
+\begin{sourcecode}
+  delta=(ppm),pos-number=sub,use-equal
+\end{sourcecode}
+
+\begin{experimental}[delta=(ppm),pos-number=sub,use-equal]
+  \sisetup{separate-uncertainty,per-mode=symbol,detect-all,range-phrase=--}
+  \data*{yield} \SI{17}{\milli\gram} yellow needles (\SI{0.04}{\milli\mole},
+  \SI{13}{\percent}).
+  %
+  \data{mp.} \SI{277}{\celsius} (DSC).
+  %
+  \NMR(600)[CDCl3] \val{2.01} (s, \#{24}, \pos{5}), \val{2.31} (s, \#{12},
+  \pos{1}), \val{6.72--6.74} (m, \#{2}, \pos{11}), \val{6.82} (s, \#{8},
+  \pos{3}), \val{7.05--7.07} (m, \#{2}, \pos{12}), \val{7.39--7.41} (m, \#{4},
+  \pos{9}), \val{7.48--7.49} (m, \#{4}, \pos{8}).
+  %
+  \NMR{13,C}(150)[CDCl3] \val{21.2} ($+$, \#{4}, \pos{1}), \val{23.4} ($+$,
+  \#{8}, \pos{5}), \val{126.0} ($+$, \#{4}, \pos{9}), \val{128.2} ($+$, \#{8},
+  \pos{3}), \val{130.8} ($+$, \#{2}, \pos{12}), \val{133.6} ($+$, \#{2},
+  \pos{11}), \val{137.0} ($+$, \#{4}, \pos{8}), \val{138.6} (q, \#{4},
+  \pos{2}), \val{140.6} (q, \#{2}, \pos{10}), \val{140.8} (q, \#{8}, \pos{4}),
+  \val{141.8} (q, \#{4}, \pos{6}), \val{145.6} (q, \#{2}, \pos{7}).
+  %
+  \data{MS}[DCP, EI, \SI{60}{\electronvolt}] \val{703} (2, \ch{M+}), \val{582}
+  (1), \val{462} (1), \val{249} (13), \val{120} (41), \val{105} (100).
+  %
+  \data{MS}[\ch{MeOH + H2O + KI}, ESI, \SI{10}{\electronvolt}] \val{720} (100,
+  \ch{M+ + OH-}), \val{368} (\ch{M+ + 2 OH-}).
+  %
+  \data{IR}[KBr] \val{3443} (w), \val{3061} (w), \val{2957} (m), \val{2918}
+  (m), \val{2856} (w), \val{2729} (w), \val{1725} (w), \val{1606} (s),
+  \val{1592} (s), \val{1545} (w), \val{1446} (m), \val{1421} (m), \val{1402}
+  (m), \val{1357} (w), \val{1278} (w), \val{1238} (s), \val{1214} (s),
+  \val{1172} (s), \val{1154} (m), \val{1101} (w), \val{1030} (w), \val{979}
+  (m), \val{874} (m), \val{846} (s), \val{818} (w), \val{798} (m), \val{744}
+  (w), \val{724} (m), \val{663} (w), \val{586} (w), \val{562} (w), \val{515}
+  (w).
+  %
+  \data*{UV-Vis} \SI{386}{\nano\metre} ($\varepsilon = \val{65984}$),
+  \SI{406}{\nano\metre} ($\varepsilon = \val{65378}$).
+  %
+  \data*{quantum yield} $\Phi = \val{0.74+-0.1}$\,.
+\end{experimental}
+
+\paragraph{Formatted List}
+Output with these options:
+
+\begin{sourcecode}
+  format=\bfseries,delta=(ppm),list=true,use-equal
+\end{sourcecode}
+
+\begin{experimental}[format=\bfseries,delta=(ppm),list=true,use-equal]
+  \sisetup{separate-uncertainty,per-mode=symbol,detect-all,range-phrase=--}
+  \data*{yield} \SI{17}{\milli\gram} yellow needles (\SI{0.04}{\milli\mole},
+  \SI{13}{\percent}).
+  %
+  \data{mp.} \SI{277}{\celsius} (DSC).
+  %
+  \NMR(600)[CDCl3] \val{2.01} (s, \#{24}, \pos{5}), \val{2.31} (s, \#{12},
+  \pos{1}), \val{6.72--6.74} (m, \#{2}, \pos{11}), \val{6.82} (s, \#{8},
+  \pos{3}), \val{7.05--7.07} (m, \#{2}, \pos{12}), \val{7.39--7.41} (m, \#{4},
+  \pos{9}), \val{7.48--7.49} (m, \#{4}, \pos{8}).
+  %
+  \NMR{13,C}(150)[CDCl3] \val{21.2} ($+$, \#{4}, \pos{1}), \val{23.4} ($+$,
+  \#{8}, \pos{5}), \val{126.0} ($+$, \#{4}, \pos{9}), \val{128.2} ($+$, \#{8},
+  \pos{3}), \val{130.8} ($+$, \#{2}, \pos{12}), \val{133.6} ($+$, \#{2},
+  \pos{11}), \val{137.0} ($+$, \#{4}, \pos{8}), \val{138.6} (q, \#{4},
+  \pos{2}), \val{140.6} (q, \#{2}, \pos{10}), \val{140.8} (q, \#{8}, \pos{4}),
+  \val{141.8} (q, \#{4}, \pos{6}), \val{145.6} (q, \#{2}, \pos{7}).
+  %
+  \data{MS}[DCP, EI, \SI{60}{\electronvolt}] \val{703} (2, \ch{M+}), \val{582}
+  (1), \val{462} (1), \val{249} (13), \val{120} (41), \val{105} (100).
+  %
+  \data{MS}[\ch{MeOH + H2O + KI}, ESI, \SI{10}{\electronvolt}] \val{720} (100,
+  \ch{M+ + OH-}), \val{368} (\ch{M+ + 2 OH-}).
+  %
+  \data{IR}[KBr] \val{3443} (w), \val{3061} (w), \val{2957} (m), \val{2918}
+  (m), \val{2856} (w), \val{2729} (w), \val{1725} (w), \val{1606} (s),
+  \val{1592} (s), \val{1545} (w), \val{1446} (m), \val{1421} (m), \val{1402}
+  (m), \val{1357} (w), \val{1278} (w), \val{1238} (s), \val{1214} (s),
+  \val{1172} (s), \val{1154} (m), \val{1101} (w), \val{1030} (w), \val{979}
+  (m), \val{874} (m), \val{846} (s), \val{818} (w), \val{798} (m), \val{744}
+  (w), \val{724} (m), \val{663} (w), \val{586} (w), \val{562} (w), \val{515}
+  (w).
+  %
+  \data*{UV-Vis} \SI{386}{\nano\metre} ($\varepsilon = \val{65984}$),
+  \SI{406}{\nano\metre} ($\varepsilon = \val{65378}$).
+  %
+  \data*{quantum yield} $\Phi = \val{0.74+-0.1}$\,.
+\end{experimental}
+
+\paragraph{Crazy}
+Output for these options:
+
+\begin{sourcecode}
+  format=\color{red}\itshape,
+  list=true,
+  delta=\textcolor{green}{\ch{M+ + H2O}},
+  pos-number=side,
+  coupling-unit=\mega\gram\per\square\second,
+  list-setup=,
+  use-equal
+\end{sourcecode}
+
+\begin{experimental}[
+    format=\color{red}\itshape,
+    list=true,
+    delta=\textcolor{green}{\ch{M+ + H2O}},
+    pos-number=side,
+    coupling-unit=\mega\gram\per\square\second,
+    list-setup=,use-equal]
+  \sisetup{separate-uncertainty,per-mode=symbol,detect-all,range-phrase=--}
+  \data*{yield} \SI{17}{\milli\gram} yellow needles (\SI{0.04}{\milli\mole},
+  \SI{13}{\percent}).
+  %
+  \data{mp.} \SI{277}{\celsius} (DSC).
+  %
+  \NMR(600)[CDCl3] \val{2.01} (s, \#{24}, \pos{5}), \val{2.31} (s, \#{12},
+  \pos{1}), \val{6.72--6.74} (m, \#{2}, \pos{11}), \val{6.82} (s, \#{8},
+  \pos{3}), \val{7.05--7.07} (m, \#{2}, \pos{12}), \val{7.39--7.41} (m, \#{4},
+  \pos{9}), \val{7.48--7.49} (m, \#{4}, \pos{8}).
+  %
+  \NMR{13,C}(150)[CDCl3] \val{21.2} ($+$, \#{4}, \pos{1}), \val{23.4} ($+$,
+  \#{8}, \pos{5}), \val{126.0} ($+$, \#{4}, \pos{9}), \val{128.2} ($+$, \#{8},
+  \pos{3}), \val{130.8} ($+$, \#{2}, \pos{12}), \val{133.6} ($+$, \#{2},
+  \pos{11}), \val{137.0} ($+$, \#{4}, \pos{8}), \val{138.6} (q, \#{4},
+  \pos{2}), \val{140.6} (q, \#{2}, \pos{10}), \val{140.8} (q, \#{8}, \pos{4}),
+  \val{141.8} (q, \#{4}, \pos{6}), \val{145.6} (q, \#{2}, \pos{7}).
+  %
+  \data{MS}[DCP, EI, \SI{60}{\electronvolt}] \val{703} (2, \ch{M+}), \val{582}
+  (1), \val{462} (1), \val{249} (13), \val{120} (41), \val{105} (100).
+  %
+  \data{MS}[\ch{MeOH + H2O + KI}, ESI, \SI{10}{\electronvolt}] \val{720} (100,
+  \ch{M+ + OH-}), \val{368} (\ch{M+ + 2 OH-}).
+  %
+  \data{IR}[KBr] \val{3443} (w), \val{3061} (w), \val{2957} (m), \val{2918}
+  (m), \val{2856} (w), \val{2729} (w), \val{1725} (w), \val{1606} (s),
+  \val{1592} (s), \val{1545} (w), \val{1446} (m), \val{1421} (m), \val{1402}
+  (m), \val{1357} (w), \val{1278} (w), \val{1238} (s), \val{1214} (s),
+  \val{1172} (s), \val{1154} (m), \val{1101} (w), \val{1030} (w), \val{979}
+  (m), \val{874} (m), \val{846} (s), \val{818} (w), \val{798} (m), \val{744}
+  (w), \val{724} (m), \val{663} (w), \val{586} (w), \val{562} (w), \val{515}
+  (w).
+  %
+  \data*{UV-Vis} \SI{386}{\nano\metre} ($\varepsilon = \val{65984}$),
+  \SI{406}{\nano\metre} ($\varepsilon = \val{65378}$).
+  %
+  \data*{quantum yield} $\Phi = \val{0.74+-0.1}$\,.
+\end{experimental}
+
+\subsection{The \chemmodule*{thermodynamics} Module}\label{sec:thermodynamics-module}
+
+The \chemmodule{thermodynamics} module loads the \pkg{siunitx}
+package~\cite{pkg:siunitx}.
+
+\subsubsection{The \cs*{state} Macro}
+
+\begin{commands}
+  \command{state}[\oarg{options}\marg{symbol}]
+    Typeset a state variable.
+\end{commands}
+
+This macro can be used to write the thermodynamic state variables.
+\begin{example}
+  \state{A}, \state[subscript-left=f]{G} ,
+  \state[subscript-right=\ch{Na}]{E},
+  \state[superscript-right=\SI{1000}{\celsius}]{H}
+\end{example}
+
+These options are available:
+\begin{options}
+  \keyval{pre}{text}\Module{thermodynamics}\Default{\cs{changestate}}
+    Code inserted before the variable.  Inserted in text mode.
+  \keyval{post}{text}\Module{thermodynamics}\Default
+    Code inserted after the variable. Inserted in text mode.
+  \keyval{superscript-left}{text}\Module{thermodynamics}\Default
+    The left superscript. Inserted in text mode.
+  \keyval{superscript-right}{text}\Module{thermodynamics}\Default{\cs{standardstate}}
+    The right superscript. Inserted in text mode.
+  \keyval{superscript}{text}\Module{thermodynamics}
+    An alias of \option{superscript-right}.
+  \keyval{subscript-left}{text}\Module{thermodynamics}\Default
+    The left subscript. Inserted in text mode.
+  \keyval{subscript-right}{text}\Module{thermodynamics}\Default
+    The right subscript. Inserted in text mode.
+  \keyval{subscript}{text}\Module{thermodynamics}
+    An alias of \option{subscript-left}.
+\end{options}
+
+\subsubsection{Thermodynamic Variables}
+
+The \chemmodule{thermodynamics} module provides a few commands for specific
+thermodynamic variables:
+\begin{commands}
+  \command{enthalpy}[\sarg\oarg{options}\darg{subscript}\marg{value}]
+    Typeset the amount of enthalpy.
+  \command{entropy}[\sarg\oarg{options}\darg{subscript}\marg{value}]
+    Typeset the amount of entropy.
+  \command{gibbs}[\sarg\oarg{options}\darg{subscript}\marg{value}]
+    Typeset the amount of Gibbs enthalpy.
+\end{commands}
+
+Their usage is pretty much self-explaining:
+\begin{example}[side-by-side]
+  \enthalpy{123} \par
+  \entropy{123} \par
+  \gibbs{123}
+\end{example}
+The argument \darg{subscript} adds a subscript for specification, \sarg\ hides
+number and unit:
+\begin{example}[side-by-side]
+    \enthalpy(r){123} \par
+    \enthalpy*{123} \par
+\end{example}
+
+\begin{options}
+  \keyval{pre}{text}\Module{thermodynamics}\Default{\cs{changestate}}
+    Code inserted before the variable.  Inserted in text mode.
+  \keyval{post}{text}\Module{thermodynamics}\Default
+    Code inserted after the variable.  Inserted in text mode.
+  \keyval{superscript-left}{text}\Module{thermodynamics}\Default
+    The left superscript.  Inserted in text mode.
+  \keyval{superscript-right}{text}\Module{thermodynamics}\Default{\cs{standardstate}}
+    The right superscript. Inserted in text mode.
+  \keyval{superscript}{text}\Module{thermodynamics}
+    An alias of \option{superscript-right}.
+  \keyval{subscript-left}{text}\Module{thermodynamics}\Default
+    The left subscript.  Inserted in text mode.
+  \keyval{subscript-right}{text}\Module{thermodynamics}\Default
+    The right subscript.  Inserted in text mode.
+  \keyval{subscript}{text}\Module{thermodynamics}
+    An alias of \option{subscript-left}.
+  \keychoice{subscript-pos}{left,right}\Module{thermodynamics}\Default{left}
+    Determines wether the subscript given in \darg{subscript} is placed to the
+    left or the right of the variable.
+  \keyval{symbol}{symbol}\Module{thermodynamics}\Default
+    The symbol of the variable.  Inserted in math mode.
+  \keyval{unit}{unit}\Module{thermodynamics}\Default
+    A valid \pkg{siunitx} unit.
+\end{options}
+
+The default values depend on the command.
+\begin{example}[side-by-side]
+  \enthalpy[unit=\kilo\joule]{-285} \par
+  \gibbs[pre=]{0} \par
+  \entropy[pre=$\Delta$,superscript=]{56.7}
+\end{example}
+The unit is set corresponding to the rules of \pkg{siunitx} and depends on
+its settings:
+\begin{example}[side-by-side]
+  \enthalpy{-1234.56e3} \par
+  \sisetup{
+    per-mode=symbol,
+    exponent-product=\cdot,
+    output-decimal-marker={,},
+    group-four-digits=true
+  }
+  \enthalpy{-1234.56e3}
+\end{example}
+
+\subsubsection{Create New Variables or Redefine Existing Ones}
+
+\begin{commands}
+  \command{NewChemState}[\marg{cs}\marg{options}]
+    Define new state commands like \cs{enthalpy}.  Gives an error is \meta{cs}
+    already exists.
+  \command{RenewChemState}[\marg{cs}\marg{options}]
+    Redefine existing state commands.
+  \command{DeclareChemState}[\marg{cs}\marg{options}]
+    Like \cs{NewChemState} but gives now error if \meta{cs} already exists.
+  \command{ProvideChemState}[\marg{cs}\marg{options}]
+    Define new state commands like \cs{enthalpy}.  Defines \meta{cs} only if
+    it is not defined, yet.
+\end{commands}
+The argument \meta{options} is a comma separated list of key/value options:
+\begin{options}
+  \keyval{pre}{text}\Module{thermodynamics}\Default{\cs{changestate}}
+    Code inserted before the variable.  Inserted in text mode.
+  \keyval{post}{text}\Module{thermodynamics}\Default
+    Code inserted after the variable.  Inserted in text mode.
+  \keyval{superscript-left}{text}\Module{thermodynamics}\Default
+    The left superscript.  Inserted in text mode.
+  \keyval{superscript-right}{text}\Module{thermodynamics}\Default{\cs{standardstate}}
+    The right superscript.
+  \keyval{superscript}{text}\Module{thermodynamics}
+    An alias of \option{superscript-right}.
+  \keyval{subscript-left}{text}\Module{thermodynamics}\Default
+    The left subscript.  Inserted in text mode.
+  \keyval{subscript-right}{text}\Module{thermodynamics}\Default
+    The right subscript.  Inserted in text mode.
+  \keyval{subscript}{text}\Module{thermodynamics}
+    An alias of \option{subscript-left}.
+  \keychoice{subscript-pos}{left,right}\Module{thermodynamics}\Default{left}
+    Determines wether the subscript given in \darg{subscript} is placed to the
+    left or the right of the variable.
+  \keyval{symbol}{symbol}\Module{thermodynamics}\Default
+    The symbol of the variable.
+  \keyval{unit}{unit}\Module{thermodynamics}\Default
+    A valid \pkg{siunitx} unit.
+\end{options}
+
+\begin{example}
+  \NewChemState\Helmholtz{ symbol=A , unit=\kilo\joule\per\mole }
+  \NewChemState\ElPot{ symbol=E , subscript-pos=right , superscript= , unit=\volt }
+  \Helmholtz{123.4} \par
+  \ElPot{-1.1} \par
+  \ElPot[superscript=0]($\ch{Sn}|\ch{Sn^2+}||\ch{Pb^2+}|\ch{Pb}$){0.01} \par
+  \RenewChemState\enthalpy{ symbol=h , unit=\joule} \par
+  \enthalpy(f){12.5}
+\end{example}
+
+The existing commands have been defined like this:
+\begin{sourcecode}
+  \NewChemState \enthalpy{ symbol = H, unit = \kilo\joule\per\mole }
+  \NewChemState \entropy { symbol = S, unit = \joule\per\kelvin\per\mole, pre = }
+  \NewChemState \gibbs   { symbol = G, unit = \kilo\joule\per\mole }
+\end{sourcecode}
+
+So -- for following thermodynamic conventions -- one could define a molar and
+an absolute variable:
+\begin{example}
+  \RenewChemState\enthalpy{symbol=h,superscript=,unit=\kilo\joule\per\mole}% molar
+  \NewChemState\Enthalpy{symbol=H,superscript=,unit=\kilo\joule}% absolute
+  \enthalpy{-12.3} \Enthalpy{-12.3}
+\end{example}
+
+\subsection{The \chemmodule*{units} Module}\label{sec:units-module}
+
+The \chemmodule{units} module loads the \pkg{siunitx}
+package~\cite{pkg:siunitx}.
+
+In chemistry some non-SI units are very common.  \pkg{siunitx} provides the
+command
+\begin{commands}
+  \command*{DeclareSIUnit}[\marg{cs}\marg{unit}]
+    Define \meta{cs} to be a valid unit command inside \pkg{siunitx}' macros
+    \cs*{SI} and \cs*{si} which represents \meta{unit}.
+\end{commands}
+to add arbitrary units.  \chemmacros\ uses that command to provide some
+units.  Like all \pkg{siunitx} units they're only valid inside
+\cs*{SI}\marg{num}\marg{unit} and \cs*{si}\marg{unit}.
+\begin{commands}
+  \command{atmosphere} \si{\atmosphere}
+  \command{atm} \si{\atm}
+  \command{calory} \si{\calory}
+  \command{cal} \si{\cal}
+  \command{cmc} \si{\cmc} \par
+    The units \cs{cmc}, \cs{molar}, and \cs{Molar} are defined by the
+    package \pkg{chemstyle} as well.  \chemmacros\ only defines them, if
+    \pkg{chemstyle} is not loaded.
+  \command{molar} \si{\molar}
+  \command{moLar} \si{\moLar}
+  \command{Molar} \si{\Molar}
+  \command{MolMass} \si{\MolMass}
+  \command{normal} \si{\normal}
+  \command{Torr} \si{\Torr}
+\end{commands}
+
+By the way: \cs*{mmHg} \si{\mmHg} already is defined by \pkg{siunitx}.
+
+\section{Internal Modules}
+
+\subsection{The \chemmodule*{tikz} Module}\label{sec:tikz-module}
+
+The \chemmodule{tikz} module loads the \pkg{tikz} package~\cite{pkg:pgf} and
+the \TikZ\ library \code{calc}.
+
+\subsubsection{For Users}
+The \chemmodule{tikz} module defines a few arrow tips:
+\begin{tikzcode}
+  \arrowtip{el}
+    An arrow tip: \verbcode+\tikz\draw[-el](0,0)--(1,0);+
+    \tikz\draw[-el](0,0)--(1,0);
+  \arrowtip{left el}
+    An arrow tip: \verbcode+\tikz\draw[-left el](0,0)--(1,0);+
+    \tikz\draw[-left el](0,0)--(1,0);
+  \arrowtip{right el}
+    An arrow tip: \verbcode+\tikz\draw[-right el](0,0)--(1,0);+
+    \tikz\draw[-right el](0,0)--(1,0);
+\end{tikzcode}
+
+The\sinceversion{5.3} \chemmodule{tikz} module also loads the libraries
+\code{calc} and \code{decorations.pathmorphing}.  It uses those libraries for
+defining a new decoration \tikzdecoration{wave}.
+\begin{example}[side-by-side]
+  \begin{tikzpicture}
+    \draw[decorate,decoration=wave] (0,0) -- (2,0) ;
+  \end{tikzpicture}
+\end{example}
+
+\subsubsection{For Module Writers}
+The \chemmodule{tikz} module provides some macros for common \TikZ\
+functions.  This allows to use expl3's powerful function variants for
+expansion control.
+
+\begin{commands}
+  \explcommand{c_chemmacros_other_colon_tl}
+    A constant tokenlist which contains a colon with category code~12 (other).
+    This is useful since \TikZ\ sometimes expects an other colon and in an
+    expl3 programming environment \code{:} has category code~11 (letter).
+  \explcommand{chemmacros_tikz_picture:nn}[ \marg{options} \marg{code}]
+    Defined as \verbcode+\tikzpicture[{#1}] #2 \endtikzpicture+.
+  \explcommand{chemmacros_tikz:nn}[ \marg{options} \marg{code}]
+    Defined as \verbcode+\tikz[{#1}]{#2}+.
+  \explcommand{chemmacros_tikz_draw:n}[ \marg{options}]
+    Defined as \verbcode+\draw[{#1}]+.
+  \explcommand{chemmacros_tikz_node:n}[ \marg{options}]
+    Defined as \verbcode+\node[{#1}]+.
+  \explcommand{chemmacros_tikz_shade:n}[ \marg{options}]
+    Defined as \verbcode+\shade[{#1}]+.
+  \explcommand{chemmacros_tikz_shadedraw:n}[ \marg{options}]
+    Defined as \verbcode+\shadedraw[{#1}]+.
+  \explcommand{chemmacros_tikz_node_in_draw:n}[ \marg{options}]
+    Defined as \verbcode+node[{#1}]+.
+\end{commands}
+
+\subsection{The \chemmodule*{xfrac} Module}\label{sec:xfrac-module}
+
+The \chemmodule{xfrac} module loads the package
+\pkg{xfrac}~\cite{bnd:l3packages}.  For the following explanations it will be
+helpful if you know about said package and how it works first.  This module is
+a support module that defines the macro
+\begin{commands}
+  \command{chemfrac}[\oarg{type}\marg{numerator}\marg{denominator}]
+    \meta{type} can either be \code{text} or \code{superscript}.
+\end{commands}
+This macro calls a certain instance of the \pkg{xfrac} \code{text} template,
+depending on the option \meta{type} and the current font family.  If used
+\cs{chemfrac} looks if an instance
+\begin{center}
+  \code{chemmacros-frac-\cs*{f@family}-\meta{type}}
+\end{center}
+exists.  If yes this instance is used, if no the instance
+\code{chemmacros-frac-default-\meta{type}} is used.  The \code{default}
+instances are the same as the ones for \code{cmr}.
+
+\begin{table}
+  \centering
+  \newcommand*\showfrac[1]{%
+    \code{#1} &
+    \fontfamily{#1}\selectfont
+    \chemfrac[text]{2}{3} &
+    \fontfamily{#1}\selectfont
+    \chemfrac[superscript]{2}{3}%
+  }
+  \caption{Predefined \chemmodule{xfrac} \code{text} instances.}
+  \label{tab:xfrac}
+  \begin{tabular}{llcc}
+    \toprule
+      \bfseries font family & \bfseries text & \bfseries superscript \\
+    \midrule
+      \showfrac{cmr} \\
+      \showfrac{lmr} \\
+      \showfrac{LinuxLibertineT-TLF} \\
+      \showfrac{LinuxLibertineT-TOsF} \\
+    \bottomrule
+  \end{tabular}
+\end{table}
+
+The \chemmodule{xfrac} module defines instances some font families, they are
+listed and demonstrated in table~\vref{tab:xfrac}.  The \code{superscript}
+type fractions \emph{look} larger than the \code{text} types.  The reason is
+that the \code{superscript} types are typically used with a smaller font size.
+Let's take a look at an example where both instances are used:
+\begin{example}[side-by-side]
+  \chemsetup[redox]{pos=top}
+  \code{superscript}:
+  \ch{"\ox{1/3,I}" {}3+}
+
+  \chemsetup[redox]{pos=side}
+  \code{text}: \ox{1/3,I3+}
+
+  \huge
+  \chemsetup[redox]{pos=top}
+  \code{superscript}:
+  \ch{"\ox{1/3,I}" {}3+}
+
+  \chemsetup[redox]{pos=side}
+  \code{text}: \ox{1/3,I3+}
+\end{example}
+
+If you define instances for other families please feel free to submit them to
+me (see section~\vref{sec:submitting-module}) so they can be added to the
+\chemmodule{xfrac} module.
+
+\appendix
+\part{Appendix}
+\section{Own Modules}\label{sec:own-modules}
+\subsection{How To}
+
+If you have additional functionality which you think might be useful as a
+\chemmacros\ module then you can easily write one yourself.  The module must
+be a file in a path where \TeX\ can find it following a certain naming
+scheme.  The file for a module \chemmodule*{foo} \emph{must be named}
+\code{chemmacros.module.foo.code.tex}.
+
+\begin{commands}
+  \command{ChemModule}[\sarg\marg{name}\marg{description}\oarg{minimal
+    compatibility version}]
+    Register module \meta{name}.  The optional argument \meta{minimal
+      compatibility version} ensures that this module is only loaded if the
+    option \option{compatibility} has a high enough version number.  If it is
+    omitted the module can be loaded in each version~5.0 or higher.
+\end{commands}
+
+The first line in the file then should look similar to this:
+\begin{sourcecode}
+  \ChemModule{foo}{2015/07/14 description of foo}
+\end{sourcecode}
+This registers module \chemmodule*{foo} which means \chemmacros\ will accept
+this file as a valid module.
+
+Since \chemmacros\ is written using expl3 \cs{ChemModule} starts an expl3
+programming environment.  If you don't want that but rather want to write your
+module using traditional \LaTeXe\ methods then use the starred variant:
+\begin{sourcecode}
+  \ChemModule*{foo}{2015/07/14 description of foo}
+\end{sourcecode}
+In both variants \code{@} has category code~11 (letter).
+
+Since new modules very likely might rely on code provided first in a certain
+version of \chemmacros\ you might want to make sure that your module only is
+loaded when the compatibility mode is high enough to provide the features you
+want:
+\begin{sourcecode}
+  \ChemModule{foo}{2015/10/14 description of foo}[5.2]
+\end{sourcecode}
+
+You should be aware that your module \emph{will not be loaded} with
+\verbcode+\usechemmodule{all}+! The pseudo-module \chemmodule{all} contains a
+manually maintained list of the modules that are loaded by it.
+
+If you decide to write your module \chemmodule*{foo} using expl3 and add
+options you want to be able to set using
+\cs{chemsetup}\Oarg{foo}\marg{options} please make sure you define (and set)
+them with the following macros:
+\begin{commands}
+  \explcommand{chemmacros_define_keys:nn}[ \marg{module} \marg{key definitions}]
+    Define l3keys options for the module \meta{module}.  This is a wrapper for
+    \explcs*{keys_define:nn} \Marg{chemmacros/\meta{module}} \marg{key
+      definitions}.
+  \explcommand{chemmacros_set_keys:nn}[ \marg{module} \marg{input}]
+    Sets l3keys options for the module \meta{module}.  This is a wrapper for
+    \explcs*{keys_set:nn} \Marg{chemmacros/\meta{module}} \marg{input}.
+\end{commands}
+Also (\emph{especially if you consider submitting the module, see
+  section~\vref{sec:submitting-module}}) please follow the expl3 naming
+conventions for variables and functions, \ie, use \code{chemmacros} as expl3
+module name:
+\begin{sourcecode}
+  \tl_new:N \l__chemmacros_my_internal_variable_tl
+  \tl_new:N \l_chemmacros_my_public_variable_tl
+  \cs_new:Npn \__chemmacros_my_internal_function:n #1 { ... }
+  \cs_new_protected:Npn \chemmacros_my_public_function:n #1 { ... }
+  \NewDocumentCommand \publicfunction {m}
+    { \chemmacros_my_public_function:n {#1} }
+\end{sourcecode}
+You will find more details on the naming conventions in \code{interface3.pdf}
+which most likely is available on your system:
+\begin{lbash}
+  texdoc interface3
+\end{lbash}
+If you haven't read section~\vref{sec:base-module} about the \chemmodule{base}
+module, yet, please have a look.  There some macros for module writers are
+described.  Also other modules define macros for module writers which may be
+useful.
+
+\subsection{Submitting a Module}\label{sec:submitting-module}
+
+If you have written a module and feel it might be useful for other users
+please feel free to contact me and submit the module.  I will surely take at
+look at both functionality and code and if I feel that it adds value to
+\chemmacros\ I will add it to the package.  Requirement for this is that the
+module is licensed with the \LPPL\ (v1.3 or later) and that I take over
+maintenance (according to the \enquote{maintainer} status of the \lppl).
+
+Please do \emph{not} submit your module via pull request but send me the files
+directly.  In the best case you also have a short piece of documentation.
+
+\section{Suggestions, Bug Reports, Support}\label{sec:sugg-bug-reports}
+
+\paragraph{Support}
+If you need support or help with anything regarding \chemmacros\ please use
+the usual support forums
+\begin{itemize}
+  \item \url{http://www.golatex.de/} or
+  \item \url{http://texwelt.de/wissen/} if you speak German,
+  \item \url{http://www.latex-community.org/forum/} or
+  \item \url{http://tex.stackexchange.com/} if you speak English
+\end{itemize}
+or go the \emph{dedicated support forum}
+\begin{itemize}
+  \item \url{http://www.mychemistry.eu/forums/forum/chemmacros/}
+\end{itemize}
+where you can be sure that I will see the question.
+  
+\paragraph{Suggestions}
+If you have any suggestions on how \chemmacros\ could be improved, adding
+missing features \etc, please feel free to contact me via
+\email{contact@mychemistry.eu}.
+
+\paragraph{Bug reports}
+If you find any bugs, \ie, errors (something not working as described,
+conflicts with other packages, \ldots) then please go to
+\url{https://github.com/cgnieder/chemmacros/issues/} and open a new issue
+describing the error including a minimal working example.
+
+\end{document}
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