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+--------------------------------------------------------------------------
+the chemexec package
+creating (chemical) exercise sheets, chemical macros
+2011/03/01
+--------------------------------------------------------------------------
+Clemens Niederberger
+eb: http://www.niederberger-berlin.net/2010/08/latex-chemische-formeln-erstellen-iiv/
+email: kontakt@niederberger-berlin.net
+--------------------------------------------------------------------------
+Copyright 2011 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.
+
+This work consists of the files chemexec.sty, chemexec_de.tex
+and chemexec_en.tex
+--------------------------------------------------------------------------
+The chemexec package provides commands for typesetting some often needed
+chemical stuff like ion charges, oxidation numbers, common ions ...
+It also provides some environments for creating exercise sheets.
+--------------------------------------------------------------------------
+If you have any ideas, questions, suggestions or bugs to report, please
+feel free to contact me.
+--------------------------------------------------------------------------
\ No newline at end of file
diff --git a/Master/texmf-dist/doc/latex/chemexec/chemexec_de.pdf b/Master/texmf-dist/doc/latex/chemexec/chemexec_de.pdf
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diff --git a/Master/texmf-dist/doc/latex/chemexec/chemexec_de.tex b/Master/texmf-dist/doc/latex/chemexec/chemexec_de.tex
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+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% ------------------------------------------------------------------------------------- %
+% - chemexec - chemexec_de.tex -------------------------------------------------------- %
+% - creating (chemical) exercise sheets, chemical macros ------------------------------ %
+% ------------------------------------------------------------------------------------- %
+% - Clemens Niederberger -------------------------------------------------------------- %
+% - 2011/03/06 ------------------------------------------------------------------------ %
+% ------------------------------------------------------------------------------------- %
+% - http://www.niederberger-berlin.net/2010/08/latex-chemische-formeln-erstellen-iiv/ - %
+% - kontakt@niederberger-berlin.net --------------------------------------------------- %
+% ------------------------------------------------------------------------------------- %
+% - If you have any ideas, questions, suggestions or bugs to report, please feel free - %
+% - to contact me. -------------------------------------------------------------------- %
+% ------------------------------------------------------------------------------------- %
+% Copyright 2011 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.                          %
+%                                                                                       %
+% This work consists of the files chemexec.sty, chemexec_de.tex                         %
+% and chemexec_en.tex                                                                   %
+% ------------------------------------------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\documentclass[a4paper,10pt,headsepline]{scrartcl}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% = PAKETE/EINSTELLUNGEN ============================================================== %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\usepackage[ngerman]{babel}                      % deutsche Sprache
+\usepackage[utf8x]{inputenc}
+\usepackage[T1]{fontenc}
+\usepackage{listings}
+\usepackage{array,slashbox}
+\setlength\extrarowheight{7pt}
+\usepackage{graphicx}
+\usepackage[exercise,exersize=large]{chemexec}
+  \usetikzlibrary{fadings,patterns}
+\usepackage{xcolor,wrapfig}
+\definecolor{dunkelblau}{rgb}{0,0.33,0.62}
+\definecolor{dunkelrot}{rgb}{0.4392,0.0627,0.0627}
+\usepackage{url,paralist}
+\usepackage[ngerman]{varioref}                   % flexibles Referenzieren
+  \labelformat{section}{Abschnitt #1}
+  \labelformat{subsection}{Abschnitt #1}
+  \labelformat{subsubsection}{Abschnitt #1}
+% = Hyperlinks ======================================================================== %
+\usepackage{hyperref}
+  \hypersetup{colorlinks=true,                   % Farben der pdf-Links verändern
+              plainpages=false,
+              linkcolor=black,
+              urlcolor=black,
+              citecolor=black,
+              bookmarksopen=true,
+              bookmarksopenlevel=2,
+              bookmarksnumbered=true,
+              pdfstartview=FitH,
+              pdfauthor={Clemens Niederberger},
+              pdftitle={chemexec},
+              pdfsubject={customizing you (chemical) exercise sheets},
+              pdfkeywords={chemexec},
+              pdfcreator={LaTeX}
+  }
+\usepackage{times,chemfig,xspace}%,stree}
+% = Listings einstellen =============================================================== %
+\lstset{
+   basicstyle={\ttfamily\footnotesize},          % Grundstil
+   extendedchars=true,
+   numbers=left,                                 % Zeilennummern
+   numberstyle=\tiny,                            % Größe des Zeilennummern
+   numberblanklines=true,                        % Leerzeilen nummerieren
+   gobble=1,                                     % das erste Leerzeichen abschneiden
+   xleftmargin=20pt,                             % Einrückung links
+   breaklines=true,                              % Zeilenumbruch
+   moredelim=[is][\color{red}]{|}{|}                    % Hervorhebung
+   }
+
+% = Kopfzeile ========================================================================= %
+\usepackage{scrpage2}
+\pagestyle{scrheadings}
+\setheadwidth{textwithmarginpar}
+\automark{section}
+\ihead{\CEx \CEversion}
+\ifoot{\small\color{gray}-~Seite~\thepage~-}
+\cfoot{}
+\ofoot{}
+
+% = Überschriften ===================================================================== %
+\setkomafont{disposition}{\rmfamily\bfseries}    % Gewicht fett und Schriftart roman
+
+% ===================================================================================== %
+\newcommand{\option}[1]{`\texttt{#1}'\xspace}
+\newcommand{\TikZ}{\mbox{Ti{\bfseries\itshape k}Z}\xspace}
+%\newcommand{\eg}{\mbox{e.\,g.}\xspace}
+\newcommand{\zB}{\mbox{z.\,B.}\xspace}
+\newlength{\chemx}
+\newlength{\chemy}
+\newcommand{\CEx}[1][8]{%
+{\color{dunkelrot}\fontfamily{pag}\fontsize{#1}{#1}\selectfont chemexec}\xspace
+}
+\let\saveversion\CEversion
+\def\CEversion{\saveversion\xspace}
+
+\begin{document}
+\begin{titlepage}
+  % inspired by the titlepage of chemfig's documentation
+  \begin{tikzpicture}[remember picture,overlay]
+    \shade [color=dunkelrot,right color=white](current page.south west) rectangle ([yshift=3cm,xshift=-3cm]current page.center);
+    \shade[top color=black,bottom color=dunkelrot]([yshift=7cm]current page.east)rectangle([yshift=2.5cm]current page.west);
+  \end{tikzpicture}
+  \begin{center}
+    \vspace*{-1.5cm}
+    \CEx[45]\par
+    \Large\CEversion\par\bigskip
+    \footnotesize\CEdate{de}\par
+    \normalsize Clemens Niederberger\par\vskip1.5cm
+    \color{white}\huge (chemische) \"Ubungsaufgabenbl\"atter%
+  \end{center}
+  \vskip3cm
+  
+\end{titlepage}
+
+\tableofcontents
+
+\section{Lizenz}
+\CEx \CEversion steht unter der LaTeX Project Public License Version 1.3 oder sp\"ater.\newline(\url{http://www.latex-project.org/lppl.txt})
+
+\section{\"Uber}
+Das \verb=chemexec= Paket stellt einige kleine Umgebungen und Befehle zur Ver\-f\"u\-gung, die ich f"ur die Verwendung in "Ubungsbl"attern und Unterrichtsskripten brauchte. So gibt es nun die \verb=definition=-Umgebung, die \verb=beispiel=-Um\-ge\-bung u.\"a. Au\ss{}erdem den einen oder anderen n\"utzlichen Befehl, der einem Schreibarbeit abnimmt.\\
+F\"ur Arbeitsbl\"atter haben sich die Aufgaben/L\"osungs-Befehle in \ref{sec:aufgaben} als recht n\"utzlich erwiesen.\\
+Das Paket ersetzt \verb=echem.sty= f"ur OCHEM von Ingo Kl"ockl\footnote{\url{http://www.2k-software.de/ingo/ochem.html}}.
+
+\section{Neu in Version \CEversion}
+\CEx ist neu \"uberarbeitet und dabei etwas verschlankt worden. die Befehle \verb=\lw=,\linebreak\verb=\lwbar=, \verb=\atomconnect= und die \verb=Schema=-Umgebung sind herausgeflogen. Dafür funktionieren jetzt alle Befehle auch mit \verb=pdflatex=, da alle Zeichungen (siehe etwa \ref{sssec:stereo}) nun mit \TikZ und nicht mehr mit pstricks erstellt werden.
+
+\section{Paket-Optionen}
+Folgende Optionen k"onnen ausgew"ahlt werden:
+\begin{itemize}
+ \item Die Option \option{chapter} "andert die Z"ahler-Einstellung f"ur die Aufgaben und L"osungen (\ref{sec:aufgaben}) und die Beispiele (\ref{subsec:beispiele}).% und die Schemas (Abschnitt \ref{subsec:schema}).
+ \item Die Option \option{color=farbe} "andert die Farbe der Nummern, mit denen die Aufgaben und L"osungen durchnummeriert werden, der Linien, die die \texttt{beispiel}-Umgebung einrahmen, und der "Uberschrift der \texttt{definition}-Umgebung (\ref{sec:definition}) in \texttt{far\-be}.\\ Default ist Dunkelblau:\\\verb=\xdefinecolor{dunkelblau}{rgb}{0,0.33,0.62}=.
+ \item Die Option \option{english} "andert die "Uberschriften der Aufgaben (Exercise), L"osungen (Solution), Beispiele (Example) und den Exkurs (Excursus).
+ \item Die Option \option{exercise} erm"oglicht das Verwenden der Befehle f"ur die Aufgaben und L"osungen.
+ \item Mit der Option \option{exersize=groesse} l"asst sich die Schriftgr"o\ss e der "Uberschriften der Aufgaben und L"osungen einstellen.
+ \item Die Option \option{here} legt f"ur die \texttt{Schema}-Gleitumgebung als Positionierung \texttt{H} (genau hier) fest.
+ \item Die Option \option{shade=boolean} "andert das prinzipielle Layout der \texttt{definition}-Umgebung, kann die Werte \texttt{true} oder \texttt{false} einnehmen, Default ist \texttt{shade=false}.
+ \item Die Option \option{shadecolor=farbe} "andert die Hintergrundfarbe der \texttt{definition}-Umgebung in \texttt{farbe}, wenn die Option `\texttt{shade}' ausgew"ahlt ist.
+ \item Die Option \option{numcolor=farbe} "andert die Farbe der Nummern, mit denen die Aufgaben und L"osungen durchnummeriert werden, in \texttt{farbe}.
+\end{itemize}
+
+\section{Neue Befehle}
+\subsection{Mathematik}
+Ich habe einige kleine Befehle definiert, die ich immer wieder brauchte:
+\begin{itemize}
+ \item \verb=\vek{}= Pfeilschreibweise f\"ur Vektoren: \verb=\vek{a}, \vek{A}= ergibt \vek{a}, \vek{A}.
+ \item \verb=$\abs{}$= Betrag: \verb=\abs{\vek{a}}, \abs{-\frac{i}{2}}= ergibt \abs{\vek{a}}, \abs{-\frac{i}{2}}.
+\end{itemize}
+Beide Befehle funktionieren sowohl in normalem Text als auch in der Ma\-the\-ma\-tik-Um\-ge\-bung.
+
+\subsection{Chemie}
+F\"ur die Chemie habe ich die folgenden Befehle immer wieder als sehr n\"utzlich empfunden.
+\subsubsection{Teilchen und Ladungen}
+\begin{itemize}
+ \item \verb=\el= Elektron: \el
+ \item \verb=\prt= Proton: \prt
+ \item \verb=\ntr= Neutron: \ntr
+ \item \verb=\Hpl= Proton: \Hpl
+ \item \verb=\Hyd= Hydroxid: \Hyd
+ \item \verb=\ox{}{}= Oxidationszahlen\\
+       \verb=Ca\ox{-1}{F}$_2$=  Ca\ox{-1}{F}$_2$;\\
+       das erste Argument ist die Oxidationszahl, das zweite das Element.
+ \item \verb=\om= und \verb=\op= Ladungen \om\ und \op.\\
+       Beide Befehle haben ein optionales Argument f"ur die Anzahl der Ladungen:\\\verb=Ca\op[2]=  Ca\op[2], \verb=\phosphat\om[3]=  \phosphat\om[3].
+\end{itemize}
+
+\subsubsection{Stereodeskriptoren}\label{sssec:stereo}
+Einige Deskriptoren zur Erleichterung der Nomenklatur.
+\begin{itemize}
+ \item \verb=\Rcip= und \verb=\Scip=, rectus und sinister: \Rcip\ \Scip
+ \item \verb=\Dfi= und \verb=\Lfi=, dexter und laevus: \Dfi\ \Lfi
+ \item \verb=\E= und \verb=\Z=, entgegen und zusammen: \E\ \Z
+ \item \verb=\rconf= und \verb=\sconf= R/S-Konfiguration: \rconf\ und \sconf. Beide Befehle haben ein optionales Argument, mit dem der Buchstabe ge"andert werden kann: \verb=\rconf[]= \rconf[]
+\end{itemize}
+\subsubsection{Anionen}
+Ebenfalls definiert sind folgende S\"aurereste:
+\begin{itemize}
+ \item \verb=\nitrat= : \nitrat
+ \item \verb=\nitrit= : \nitrit
+ \item \verb=\sulfat= : \sulfat
+ \item \verb=\sulfit= : \sulfit
+ \item \verb=\phosphat= : \phosphat
+ \item \verb=\phosphit= : \phosphit
+ \item \verb=\carbonat= : \carbonat
+\end{itemize}
+Alle Chemie-Befehle sind sowohl im Text- als auch im Mathematik-Modus einsetzbar.
+
+\subsubsection{Kompatibilit"at mit \texttt{mhchem.sty}}
+Die Chemie-Befehle sind auch in den Formelsatz-Befehlen (\verb=\ce{}= u."a.) des `mhchem'-Pakets von Martin Hensel\footnote{\url{http://www.ctan.org/tex-archive/macros/latex/contrib/mhchem/}} einsetzbar. Tats"achlich l"adt \CEx `mhchem' (in der Version 3) automatisch, falls es vorhanden ist. Es muss also nur dann geladen werden, wenn ihm Optionen mitgegeben werden sollen.
+\begin{lstlisting}[numbers=none,basicstyle=\normalsize\ttfamily,showspaces=true]
+ \ce{2| |\ox{0}{Ca} +| |\ox{0}{O}_2 ->T[{~~~REDOX~~~}] 2Ca| |\op[2] + 2O| |\om[2]}
+\end{lstlisting}
+\ce{ 2 \ox{0}{Ca} + \ox{0}{O}_2 ->T[{~~~REDOX~~~}] 2Ca \op[2] + 2O \om[2] }\\
+Beachten Sie bitte, dass Sie die L"ucke vor \verb=\om=, \verb=\op=, \verb=\ox{}{}= lassen sollten, sonst kann das zu Fehlermeldungen oder falscher Darstellung f"uhren:\\
+\verb=\ce{Ca\op[2]}=  \ce{ Ca\op[2] }
+
+\noindent Weitere Beispiele:
+\begin{lstlisting}[numbers=none,basicstyle=\normalsize\ttfamily]
+ \begin{align*}
+  \cee{Na                  &->T[ox] Na\op|{}| + \el}\\
+  \cee{HCl_{aq}            &<=>> H\op_{aq} + Cl\om_{aq}}\\
+  \cee{H2O                 &<<=> \Hpl + \Hyd}\\
+  \cee{CaCl2 + H2\sulfat|{}| &-> Ca\sulfat|{}| v + 2 HCl}
+ \end{align*}
+\end{lstlisting}
+\begin{align*}
+ \cee{Na                  &->T[ox] Na\op{} + \el}\\
+ \cee{HCl_{aq}            &<=>> H\op_{aq} + Cl\om_{aq}}\\
+ \cee{H2O                 &<<=> \Hpl + \Hyd}\\
+ \cee{CaCl2 + H2\sulfat{} &-> Ca\sulfat{} v + 2 HCl}
+\end{align*}
+\CEx sollte \emph{nach} `mhchem' eingebunden werden, wenn Sie das `mhchem' Paket Laden, um ihm Optionen mitzugeben.
+
+\subsubsection{Befehle f"ur `mhchem'}
+\CEx stellt einige Befehle f"ur das Erstellen von Reaktionen mit `mhchem' zur Verf"ugung:
+\begin{lstlisting}
+ nummerierte Reaktion:
+ \reaction{2 H2 + O2 -> 2 H2O}%
+ unnummerierte Reaktion:
+ \reaction*{2 CO + O2 -> 2 CO2}
+ mehrere ausgerichtete Reaktionen:
+ \reactions{Cl_2 ||&||-> 2 Cl. ||\\|| Cl. + CH4 ||&||-> HCl + {}.CH3}
+\end{lstlisting}
+nummerierte Reaktion:
+\reaction{2 H2 + O2 -> 2 H2O}%
+unnummerierte Reaktion:
+\reaction*{2 CO + O2 -> 2 CO2}
+mehrere ausgerichtete Reaktionen:
+\reactions{Cl2 &-> 2 Cl. \\ Cl. + CH4 &-> HCl + {}.CH3}
+
+\section{Neue Umgebungen}
+\subsection{Die {\ttfamily beispiel}-Umgebung}\label{subsec:beispiele}
+F\"ur \"Ubungsbl\"atter und \"ahnliches ben\"otigte ich immer wieder eine Umgebung, die Beispiele hervorhebt und durchnummeriert:
+\begin{lstlisting}
+ |\begin{beispiel}|
+  Ein Beispiel.
+ |\end{beispiel}|
+\end{lstlisting}
+Das ergibt folgenden Output:
+\begin{beispiel}
+ Ein Beispiel.
+\end{beispiel}
+\noindent Wenn man ein zweites Beispiel im gleichen Rahmen bringen m\"ochte, kann man den Befehl \verb=\bsp=
+verwenden:
+\begin{lstlisting}
+ \begin{beispiel}
+  Ein erstes Beispiel.
+  |\bsp|
+  Ein zweites.
+ \end{beispiel}
+\end{lstlisting}
+%\setcounter{beispiel}{0}
+\begin{beispiel}
+ Ein erstes Beispiel.
+ \bsp
+ Ein zweites.
+\end{beispiel}
+
+\subsubsection{Die Optionen \texttt{color}, \texttt{linecolor} \&\ \texttt{english}}
+Die Paket-Option \option{linecolor=farbe} erm"oglicht, die Default-Farbe der umschlie\ss enden Linien zu "andern. Zum Beispiel ergibt
+\begin{lstlisting}
+ % Pr"aambel:
+ \usepackage|[linecolor={rgb:red,4;green,6}]|{chemexec}
+ % im Dokument:
+ \begin{beispiel}
+  Gr"une Linien per Paketoption.
+ \end{beispiel}
+\end{lstlisting}
+folgenden Output:
+\begin{beispiel}[linecolor={rgb:red,4;green,6}]
+ Gr"une Linien per Paketoption.
+\end{beispiel}
+\noindent Auch die Paket-Option \option{color=farbe} "andert die Farben der Linien, wirkt sich aber noch auf weitere Befehle wie die \texttt{definition}-Umgebung aus.\\
+Mit der Befehls-Option \option{linecolor=farbe} kann man auch die Farbe eines konkreten Beispiels "andern. So ergibt
+\begin{lstlisting}
+ \begin{beispiel}|[linecolor=purple]|
+  Die purpurne Einzelversion.
+ \end{beispiel}
+\end{lstlisting}
+folgenden Output:
+\begin{beispiel}[linecolor=purple]
+ Die purpurne Einzelversion.
+\end{beispiel}
+\noindent Die Paket-Option \option{english} erzeugt die englische "Uberschrift `Example'.
+\subsubsection{Unnummerierte Beispiele}
+Wenn Sie gerne unnummerierte Beispiele m"ogen oder die Beispiele mit Buchstaben durch\-z"ah\-len wollen, k"onnen Sie das wie "ublich mit der Neudefinition der Z"ahlerausgabe realisieren.
+\begin{lstlisting}
+ \renewcommand{\thebeispiel}{}
+ \begin{beispiel}
+  Jetzt ohne Z"ahler!
+ \end{beispiel}
+\end{lstlisting}
+\renewcommand{\thebeispiel}{}
+\begin{beispiel}
+ Jetzt ohne Z"ahler!
+\end{beispiel}
+\begin{lstlisting}
+ \renewcommand{\thebeispiel}{\alph{beispiel})}
+ \begin{beispiel}
+  Oder alphabetisch \ldots
+ \end{beispiel}
+\end{lstlisting}
+\renewcommand{\thebeispiel}{\alph{beispiel})}
+\begin{beispiel}
+ Oder alphabetisch \ldots
+\end{beispiel}
+
+\subsection{Die {\ttfamily definition}-Umgebung}\label{sec:definition}
+Die \texttt{definition}-Umgebung erstellt einen Kasten mit farbiger \"Uberschrift:
+\begin{lstlisting}
+ |\begin{definition}|
+  Der Betrag eines Vektors betr\"agt
+  \begin{equation}
+   |\abs{\vek{|a|}}|=\sqrt{a_x^2+a_y^2+a_z^2}
+  \end{equation}
+ |\end{definition}|
+\end{lstlisting}
+\begin{definition}
+ Der Betrag eines Vektors betr\"agt:
+ \begin{equation}
+  \abs{\vek{a}}=\sqrt{a_x^2+a_y^2+a_z^2}
+ \end{equation}
+\end{definition}
+
+\subsubsection{Die Optionen \texttt{shade}, \texttt{shadecolor} \& \texttt{color}}
+Mit der Umgebungs-Option \option{shade=boolean} "andert sich das Layout:
+\begin{lstlisting}
+ \begin{definition}|[shade=true]|
+  Der Betrag eines Vektors betr\"agt
+  \begin{equation}
+   \abs{\vek{a}}=\sqrt{a_x^2+a_y^2+a_z^2}
+  \end{equation}
+ \end{definition}
+\end{lstlisting}
+%\setcounter{equation}{0}
+\begin{definition}[shade=true]
+ Der Betrag eines Vektors betr\"agt:
+ \begin{equation}
+  \abs{\vek{a}}=\sqrt{a_x^2+a_y^2+a_z^2}
+ \end{equation}
+\end{definition}
+Mit den Optionen \option{shadecolor=farbe} und \option{color=farbe} l"asst sich das Layout noch weiter beeinflussen:
+\begin{lstlisting}
+ \begin{definition}|[shade=true,shadecolor=green!15,color=black]|
+  Der Betrag eines Vektors betr\"agt
+  \begin{equation}
+   \abs{\vek{a}}=\sqrt{a_x^2+a_y^2+a_z^2}
+  \end{equation}
+ \end{definition}
+\end{lstlisting}
+\begin{definition}[shade=true,shadecolor=green!15,color=black]
+ Der Betrag eines Vektors betr\"agt:
+ \begin{equation}
+  \abs{\vek{a}}=\sqrt{a_x^2+a_y^2+a_z^2}
+ \end{equation}
+\end{definition}
+Die Optionen \option{shade=boolean} und \option{shadecolor=farbe} sind auch als Paketoptionen einsetzbar. Damit l"asst sich das grunds"atzliche Aussehen der K"asten einstellen. Die Option \option{color=farbe} ist ebenfalls als Paket-Option einsetzbar, wirkt sich dann aber nicht nur auf die \texttt{definition}-Umgebung aus.
+\begin{lstlisting}
+ % Pr"aambel:
+ \usepackage|[shade=true,shadecolor=yellow!15]|{chemexec}
+ % im Dokument:
+ \begin{definition}
+  Der Betrag ...
+ \end{definition}
+\end{lstlisting}
+\begin{definition}[shade=true,shadecolor=yellow!15]
+ Der Betrag eines Vektors betr\"agt:
+ \begin{equation}
+  \abs{\vek{a}}=\sqrt{a_x^2+a_y^2+a_z^2}
+ \end{equation}
+\end{definition}
+
+\subsubsection{Die \texttt{defformel}-Umgebung}
+Zus"atzlich gibt es die \texttt{defformel}-Umgebung, die lediglich einen wei\ss{}en Hintergrund erzeugt und ein optionales Argument f"ur die Breite des wei\ss en Kastens besitzt\footnote{Die chemische Struktur wurde mit Hilfe des stree\TeX-Pakets von Igor Strokov erstellt.}.
+\begin{lstlisting}
+ \begin{definition}[shade=true]
+  Ein Kohlenstoffatom mit vier verschiedenen Substituenten nennt man \textbf{chiral}. Chiralit"atszentren werden oft mit einem \textasteriskcentered\ markiert.
+  |\begin{defformel}[.5\textwidth]|
+   \chemfig{R_1-[:30](-[2]R_2)(-[6]R_3)(-[:30,.15,,,white]{\text{\textasteriskcentered}})-[:-30]R_4}
+  |\end{defformel}|
+ \end{definition}
+\end{lstlisting}
+
+\begin{definition}[shade=true]
+  Ein Kohlenstoffatom mit vier verschiedenen Substituenten nennt man \textbf{chiral}. Chiralit"atszentren werden oft mit einem \stec\ markiert.
+  \begin{defformel}[.5\textwidth]
+   \chemfig{R_1-[:30](-[2]R_2)(-[6]R_3)(-[:30,.15,,,white]{\text{\stec}})-[:-30]R_4}
+  \end{defformel}
+ \end{definition}
+
+\subsection{Die \texttt{exkurs}-Umgebung}
+Die \texttt{exkurs}-Umgebung ist dazu gedacht, in B"uchern oder l"angeren Texten einen Exkurs "uber ein Thema optisch hervorzuheben und einen Eintrag ins Inhaltsverzeichnis hinzuzuf"ugen.
+\begin{lstlisting}[numbers=none,basicstyle=\normalsize\ttfamily]
+ \begin{exkurs}[options]{titel}
+  ...
+ \end{exkurs}
+\end{lstlisting}
+Es gibt zwei Optionen: \option{toc=toclevel} mit der Default-Einstellung \verb=section= und\linebreak\option{color=farbe} mit der Default-Einstellung \verb=dunkelblau=.
+\begin{lstlisting}
+ |\begin{exkurs}[color=-yellow]{Lorem ipsum}|
+  Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. ...
+ |\end{exkurs}|
+\end{lstlisting}
+\begin{exkurs}[color=-yellow,toc=paragraph]{Lorem ipsum}
+ Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zuril delenit augue duis dolore te feugait nulla facilisi.
+\end{exkurs}
+Die Paket-Option \option{color=farbe} wirkt sich ebenfalls auf die Farbe der Einsch"ube aus, mit der Paket-Option \option{english} wird die "Uberschrift in `excursus' ge"andert.
+
+\section[Aufgaben/L\"osungen]{Die Option \texttt{exercise}: Nummerierte Aufgaben/L\"osungen}\label{sec:aufgaben}
+Als eigentlicher Kern des Pakets ist ein Z\"ahler/eine \"Uberschrift f\"ur Aufgaben definiert, die man mit der Option \option{exercise} aktivieren kann. Die Aufgaben erhalten als De\-fault-\"U\-ber\-schrift `Aufgabe', k\"onnen aber eine beliebige andere als Argument bekommen. Die Nummern sind farbig. Der Befehl lautet:
+\begin{lstlisting}[numbers=none,basicstyle=\normalsize\ttfamily]
+ \aufgabe{aufgabentitel}
+\end{lstlisting}
+Da ich gerne auch die M\"oglichkeit habe, die L\"osungen anzugeben, habe ich zudem die Befehle
+\begin{lstlisting}[numbers=none,basicstyle=\normalsize\ttfamily]
+ \loesung[aufgabentitel]{Loesung} % Loesung eingeben
+ \doloesung % Loesung kapitelweise ausgeben
+ \makeloesung % Loesungen auf einmal ausgeben
+\end{lstlisting}
+definiert. In den ersten Befehl \verb=\loesung{}= gibt man die L\"osung der Aufgabe ein, eventuell mit dem Aufgabentitel als optionalem Argument. Er sollte immer direkt nach der zugeh\"origen Aufgabe eingesetzt werden. Der zweite Befehl \verb=\doloesung= erzeugt die Ausgabe der L\"osungen, die in der aktuellen \verb=\section= gesammelt wurden und der dritte Befehl \verb=\makeloesung= erzeugt alle gesammelten L\"osungen auf einmal. Beachten Sie, dass \verb=\doloesung= und \verb=\makeloesung= einander ausschlie\ss{}en. Sie m\"ussen Sich f\"ur eine von beiden Varianten entscheiden.\\
+F\"ur die Ausgabe der L\"osungen ist es unerheblich, ob man jeder Aufgabe eine L\"osung zugewiesen hat. \verb=\makeloesung= sollte sinnvollerweise erst \emph{nach allen Aufgaben} gesetzt werden und \emph{\textbf{kann nur einmal aufgerufen werden}}.
+
+\subsection{Optionen}
+Die Option\option{exersize=groesse} erm"oglicht die Einstellung der Schriftgr"osse der "Uberschriften. Erlaubt sind die bekannten Varianten: \texttt{tiny}, \texttt{scriptsize}, \texttt{footnotesize}, \texttt{small}, \texttt{normalsize}, \texttt{large}, \texttt{Large}, \texttt{LARGE}, \texttt{huge} und \texttt{Huge}. Die Default-Einstellung ist \texttt{normalsize}.\\
+Mit der Paket-Option \option{numcolor=farbe} kann man die Farbe der Nummern in \texttt{farbe} "andern. Die Paket-Option \option{english} erzeugt die englischen "Uberschriften `Exercise' bzw. `Solution'.\\
+In der Default-Einstellung werden die Nummern der Aufgaben mit jeder neuen \texttt{section} zur"uckgesetzt. Die Paket-Option \option{chapter} "andert die Einstellung, so dass der Z"ahler mit einem neuen \texttt{chapter} zur"uckgesetzt wird.
+\subsection{Die {\ttfamily alphlist}-Umgebung}
+Mit der \texttt{alphlist}-Umgebung steht eine Liste zur Verf"ugung, die z.B. Aufgaben automatisch mit a), b) etc. durchz"ahlt.
+\begin{lstlisting}
+ \begin{alphlist}
+  \item erster Punkt
+  \item zweiter Punkt
+ \end{alphlist}
+\end{lstlisting}
+\begin{alphlist}
+ \item erster Punkt
+ \item zweiter Punkt
+\end{alphlist}
+
+\subsection{Beispiel}
+In folgendem Listing k"onnen Sie die Aufgaben und den Befehl \texttt{\textbackslash doloesung} einmal im Einsatz sehen. Das Ergebnis sehen Sie direkt im Anschluss.
+\begin{lstlisting}
+ % Pr"aambel:
+ \usepackage|[exercise,exersize=large]|{chemexec}
+ % Im Dokument:
+ \par{\Large\bfseries\noindent Aufgaben}
+ |\aufgabe{}|
+  Geben Sie die Protolysereaktionen von Phosphors"aure an.|\loesung{|\ce{H3PO4 <=> \Hpl{} + H2PO4\om{} <=> 2\Hpl{} + HPO4 \om[2]{} <=> 3\Hpl{} + PO4 \om[3]}|}|
+ |\aufgabe{|Oxidationszahlen|}|
+  Welche Oxidationsstufe hat der Stickstoff in den folgenden Verbindungen: Ammoniak, Stickstoffmonoxid, Stickstoffdioxid, Salpeters"aure?|\loesung[|Oxidationszahlen|]{|
+  \ce{ \ox{-3}{N} H3}, \ce{ \ox{+2}{N} O}, \ce{ \ox{+4}{N} O2}, \ce{H \ox{+5}{N} O3}|}|
+ |\aufgabe{|Nomenklatur|}|
+  Benennen Sie folgende Molek"ule:\\\setatomsep{1.4em}
+  \begin{inparaenum}[a)]
+   \item\chemfig{-[::30](=[::60]O)-[::-60]OH}
+   \item\chemfig{-[::30](=[::60]O)-[::-60]O-[::60]-[::-60]}
+   \item\chemfig{HO-[::-30](=[::-60]O)-[::60]-[::-60]-[::60](=[::60]O)-[::-60]OH}
+  \end{inparaenum}
+ |\loesung[|Nomenklatur|]{|
+  \begin{inparaenum}[a)]
+   \item Ethans"aure
+   \item Ethans"aureethylester
+   \item Butandis"aure
+  \end{inparaenum}
+ |}|
+ |\aufgabe{}|
+  Zeichnen Sie die Strukturformel von Glycerin. Geben Sie den systematischen Namen nach IUPAC an.
+ |\loesung{\chemname{\chemfig{HO-[::-30]-[::60](-[::60]OH)-[::-60]-[::60]OH}}{1,2,3-Propantriol}}|
+ \vspace{\baselineskip}
+ \par{\Large\bfseries\noindent L\"osungen}
+ |\doloesung|
+\end{lstlisting}
+\par{\Large\bfseries\noindent Aufgaben}
+\aufgabe{}
+ Geben Sie die Protolysereaktionen von Phosphors"aure an.\loesung{\ce{H3PO4 <=> \Hpl{} + H2PO4\om{} <=> 2\Hpl{} + HPO4 \om[2]{} <=> 3\Hpl{} + PO4 \om[3]}}
+\aufgabe{Oxidationszahlen}
+ Welche Oxidationsstufe hat der Stickstoff in den folgenden Verbindungen: Ammoniak, Stickstoffmonoxid, Stickstoffdioxid, Salpeters"aure?\loesung[Oxidationszahlen]{\ce{ \ox{-3}{N} H3}, \ce{ \ox{+2}{N} O}, \ce{ \ox{+4}{N} O2}, \ce{H \ox{+5}{N} O3}}
+\aufgabe{Nomenklatur}
+ Benennen Sie folgende Molek"ule:\\\setatomsep{1.4em}
+ \begin{inparaenum}[a)]
+  \item\chemfig{-[::30](=[::60]O)-[::-60]OH} \item \chemfig{-[::30](=[::60]O)-[::-60]O-[::60]-[::-60]} \item \chemfig{HO-[::-30](=[::-60]O)-[::60]-[::-60]-[::60](=[::60]O)-[::-60]OH}
+ \end{inparaenum}
+ \loesung[Nomenklatur]{
+ \begin{inparaenum}[a)]
+ \item Ethans"aure
+ \item Ethans"aureethylester
+ \item Butandis"aure
+ \end{inparaenum}
+}
+\aufgabe{}
+ Zeichnen Sie die Skelettformel von Glycerin. Geben Sie den systematischen Namen nach IUPAC an.
+\loesung{\chemname{\chemfig{HO-[::-30]-[::60](-[::60]OH)-[::-60]-[::60]OH}}{1,2,3-Propantriol}}
+\newpage
+\par{\Large\bfseries\noindent L\"osungen}
+\doloesung
+
+\section{Ersatz f"ur \texttt{echem.sty}}
+Das Paket \verb=echem.sty= geh"ort zum OCHEM-Programm von Ingo Kl"ockl\footnote{\url{http://www.2k-software.de/ingo/ochem.html}}. Es erm"oglicht die Darstellung von Elektronen als Punkten und Elektronenpaaren als Strichen an Atome. Die Definition der `lw'-Befehle orientiert sich an den Definitionen des `echem'-Pakets. Zus"atzlich stellt \verb=echem.sty= die beiden Makros \verb=\sbond= und \verb=\dbond= zur Verf"ugung, die es erlauben, im normalen Text eine Einzel- bzw. Doppelbindung darzustellen. Diese beiden Befehle werden im `mhchem'-Paket von Martin Hensel ebenfalls definiert.
+\begin{itemize}
+ \item `mhchem'-Version:
+ \begin{itemize}
+  \item\texttt{\textbackslash ce\{F\textbackslash sbond F\}}: \ce{F\sbond F}
+  \item\texttt{\textbackslash ce\{O\textbackslash dbond O\}}: \ce{O\dbond O}
+ \end{itemize}
+ \item\newcommand{\sibond}{\,\ensuremath{\cdot}\,}\newcommand{\dobond}{\,=\,} `echem'-Version:
+ \begin{itemize}
+  \item\texttt{F\textbackslash sbond F}: F\sibond F
+  \item\texttt{O\textbackslash dbond O}: O\dobond O
+ \end{itemize}
+\end{itemize}
+Um keine Konflikte mit `mhchem' zu provozieren, liefert \CEx abgesehen von diesen beiden Befehlen und den Makros \verb=\2= und \verb=\3= die gleiche Funktionalit"at wie `echem' und kann an dessen Stelle in der \texttt{chemspecial}-Umgebung von OCHEM verwendet werden.
+\begin{lstlisting}
+ % Pr"aambel
+ \usepackage{ochem,chemexec}
+ % im Dokument:
+ \begin{chemspecial}
+  |package("chemexec")|
+ \end{chemspecial}
+ \begin{chemistry}
+  formula(L,R){
+    bond(30;-30;30)
+    branch { bond(90,=C)
+             atom("|\vdd{|O|}|O\vdd{O}");
+           }
+    bond(-30;30;-30)
+    atom("|\hdl[\echhbar]{|O|}\hdu|[\echhbar]|{|O|}|O",L,R)
+    bond(30;-30)
+  }
+ \end{chemistry}
+\end{lstlisting}
+\includegraphics{./formel.jpg}%\\% formel.jpg: 131x44 pixel, 100dpi, 3.33x1.12 cm, bb=0 0 94 32
+
+\section{Nachwort}
+Auch wenn ich mich bemüht habe, sinnvolle chemische Reaktionen einzusetzen, habe ich nicht extra überprüft, ob jedes Beispiel chemisch sinnvoll ist. Vertrauen Sie den Beispielen diesbezüglich nicht, sondern sehen Sie in einem Lehrbuch der Chemie nach
+\end{document}
\ No newline at end of file
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@@ -0,0 +1,566 @@
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% ------------------------------------------------------------------------------------- %
+% - chemexec - chemexec_en.tex -------------------------------------------------------- %
+% - creating (chemical) exercise sheets, chemical macros ------------------------------ %
+% ------------------------------------------------------------------------------------- %
+% - Clemens Niederberger -------------------------------------------------------------- %
+% - 2011/03/06 ------------------------------------------------------------------------ %
+% ------------------------------------------------------------------------------------- %
+% - http://www.niederberger-berlin.net/2010/08/latex-chemische-formeln-erstellen-iiv/ - %
+% - kontakt@niederberger-berlin.net --------------------------------------------------- %
+% ------------------------------------------------------------------------------------- %
+% - If you have any ideas, questions, suggestions or bugs to report, please feel free - %
+% - to contact me. -------------------------------------------------------------------- %
+% ------------------------------------------------------------------------------------- %
+% Copyright 2011 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.                          %
+%                                                                                       %
+% This work consists of the files chemexec.sty, chemexec_de.tex                         %
+% and chemexec_en.tex                                                                   %
+% ------------------------------------------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\documentclass[DIV10]{scrartcl}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% = PAKETE/EINSTELLUNGEN ============================================================== %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\usepackage[english]{babel}
+\usepackage[utf8x]{inputenc}
+\usepackage[T1]{fontenc}
+\usepackage{listings}
+\usepackage{array,slashbox}
+\setlength\extrarowheight{7pt}
+\usepackage{graphicx}
+\usepackage[exercise,exersize=large,english]{chemexec}
+  \usetikzlibrary{fadings,patterns}
+\usepackage{xcolor,wrapfig}
+\definecolor{dunkelblau}{rgb}{0,0.33,0.62}
+\definecolor{dunkelrot}{rgb}{0.4392,0.0627,0.0627}
+\usepackage{url,paralist}
+\usepackage[perpage,multiple]{footmisc}          % Fußnoten
+\usepackage[english]{varioref}                   % flexibles Referenzieren
+  \labelformat{section}{section #1}
+  \labelformat{subsection}{section #1}
+  \labelformat{subsubsection}{section #1}
+% = Hyperlinks ======================================================================== %
+\usepackage{hyperref}
+  \hypersetup{colorlinks=true,                   % Setup der Hyperlinks und des pdf
+              linkcolor=black,
+              urlcolor=blue!70,
+              citecolor=black,
+              plainpages=false,
+              bookmarksopen=true,
+              bookmarksopenlevel=1,
+              bookmarksnumbered=true,
+              pdfstartview=FitH,,
+              pdfauthor={Clemens Niederberger},
+              pdftitle={chemexec},
+              pdfsubject={customizing you (chemical) exercise sheets},
+              pdfkeywords={chemexec},
+              pdfcreator={LaTeX}
+  }
+\usepackage{times,amssymb,chemfig,xspace}
+% = Listings einstellen =============================================================== %
+\lstset{
+   basicstyle={\ttfamily\footnotesize},          % Grundstil
+   extendedchars=true,
+   numbers=left,                                 % Zeilennummern
+   numberstyle=\tiny,                            % Größe des Zeilennummern
+   numberblanklines=true,                        % Leerzeilen nummerieren
+   gobble=1,                                     % das erste Leerzeichen abschneiden
+   xleftmargin=20pt,                             % Einrückung links
+   breaklines=true,                              % Zeilenumbruch
+   moredelim=[is][\color{red}]{||}{||}                    % Hervorhebung
+   }
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - Kopf- und Fußzeile ---------------------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\usepackage{scrpage2}
+\pagestyle{scrheadings}
+\setheadwidth{textwithmarginpar}
+\automark{section}
+\ihead{\CEx \CEversion}
+\ifoot{\small\color{gray}-~page~\thepage~-}
+\cfoot{}
+\ofoot{}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - Komascript ------------------------------------------------------------------------ %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\setkomafont{disposition}{\rmfamily\bfseries}    % Gewicht fett und Schriftart roman
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - neue Befehle ---------------------------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\newcommand{\option}[1]{`\texttt{#1}'\xspace}
+\newcommand{\TikZ}{\mbox{Ti{\bfseries\itshape k}Z}\xspace}
+\newcommand{\eg}{\mbox{e.\,g.}\xspace}
+%\newcommand{\zB}{\mbox{z.\,B.}\xspace}
+\newlength{\chemx}
+\newlength{\chemy}
+\newcommand{\CEx}[1][8]{%
+{\color{dunkelrot}\fontfamily{pag}\fontsize{#1}{#1}\selectfont chemexec}\xspace
+}
+\let\saveversion\CEversion
+\def\CEversion{\saveversion\xspace}
+
+\begin{document}
+\begin{titlepage}
+  % inspired by the titlepage of chemfig's documentation
+  \begin{tikzpicture}[remember picture,overlay]
+    \shade [color=dunkelrot,right color=white](current page.south west) rectangle ([yshift=3cm,xshift=-3cm]current page.center);
+    \shade[top color=black,bottom color=dunkelrot]([yshift=7cm]current page.east)rectangle([yshift=2.5cm]current page.west);
+  \end{tikzpicture}
+  \begin{center}
+    \vspace*{-1.5cm}
+    \CEx[45]\par
+    \Large\CEversion\par\bigskip
+    \footnotesize\CEdate{en}\par
+    \normalsize Clemens Niederberger\par\vskip1.5cm
+    \color{white}\huge creating (chemical) exercise sheets%
+  \end{center}
+  \vskip3cm
+  
+\end{titlepage}
+
+\tableofcontents
+
+\section{Licence}
+\CEx \CEversion underlies the LaTeX Project Public License Version 1.3 or any later version.\newline(\url{http://www.latex-project.org/lppl.txt})
+
+\section{About}
+The \CEx package provides some environments and commands I needed when I created exercise sheets and other teaching material. There is a \verb=definition= environment, the \verb=beispiel= environment for examples (`beispiel' is german for example) and lots of other little commands I found useful.\\
+For the exercise sheets I especially wanted an easy way to create numbered exercises and a flexible way to print out the corresponding solutions (see \ref{sec:aufgaben}).\\
+\CEx also replaces \verb=echem.sty= for OCHEM\footnote{by Ingo Kl\"ockl \url{http://tug.ctan.org/tex-archive/support/ochem/}}.
+
+\section{New in version \CEversion}
+\CEx lost the commands \verb=\lw=, \verb=\lwbar=, \verb=\atomconnect= and the \verb=Schema= environment, because Lewis formul\ae\ can more easily be created with the `ChemFig' package and several other packages (\eg myChemistry) also provide reaction scheme environments.\\
+\CEx now nicely works with \verb=pdflatex=, since there are no more commands using pstricks. I used \TikZ instead.
+
+\section{Package options}
+You can load \CEx with different options:
+\begin{itemize}
+ \item The \verb=chapter= option changes the counter of the exercises and solutions (see \ref{sec:aufgaben}) and of the \verb=beispiel= environment (see \ref{ssec:beispiele}).
+ \item The \verb+color=<color>+ changes the color of the numbers with which the exercises ans solutions are numbered. It also changes the color of the lines bordering the \verb=beispiel= environments and the color of the title of the \verb=definition= environment.\\
+ Default color is \verb=dunkelblau= defined by\\
+ \verb=\xdefinecolor{dunkelblau}{rgb}{0,0.33,0.62}=.
+ \item The \verb=english= option changes the german titles into english ones: "Aufgabe" $\leftrightarrow$ "Exercise", "L\"osung" $\leftrightarrow$ "Solution", "Beispiel" $\leftrightarrow$ "Example" and "Exkurs" $\leftrightarrow$ "Excursus".
+ \item The \verb=exercise= option activates the commands for creating exercises and the corresponding solutions.
+ \item The \verb+exersize=<fontsize>+ changes the fontsize of the titles of the exercises and their solutions.
+ %\item Die Option \option{here} legt f"ur die \texttt{Schema}-Gleitumgebung als Positionierung \texttt{H} (genau hier) fest.
+ \item The \verb+shade=<boolean>+ changes the layout of the \verb=definition= environment. Default is \verb=false=.
+ \item The option \verb+shadecolor=<color>+ changes the background color of the\\ \verb=definition= environment if the option \verb+shade=true+ is used. Default is \verb=pink!50=.
+ \item The \verb+numcolor=<color>+ changes the color of the numbers numbering the exercises and solutions.
+\end{itemize}
+
+\section{New commands}
+\subsection{Maths}
+Just some small macros I found useful:
+\begin{itemize}
+ \item \verb=\vek{}= writing vectors with an arrow: \verb=\vek{a}, \vek{A}= \vek{a}, \vek{A}.
+ \item \verb=$\abs{}$= absolute value: \verb=\abs{\vek{a}}, \abs{-\frac{i}{2}}= \abs{\vek{a}}, \abs{-\frac{i}{2}}.
+\end{itemize}
+These commands can be used both in math mode and in text mode.
+
+\subsection{Chemistry}
+More macros I found useful. All chemistry commands can be used both in math mode and in text mode.
+\subsubsection{Particles ans charges}
+\begin{itemize}
+ \item \verb=\el= electron: \el
+ \item \verb=\prt= proton: \prt
+ \item \verb=\ntr= neutron: \ntr
+ \item \verb=\Hpl= proton: \Hpl
+ \item \verb=\Hyd= hydroxide: \Hyd
+ \item \verb=\ox{}{}= oxidation states\\
+       \verb=Ca\ox{-1}{F}$_2$=  Ca\ox{-1}{F}$_2$;\\
+       the first argument is the oxidation state, the second one the element.
+ \item \verb=\om= and \verb=\op= charges \om\ und \op.\\
+       These commands have an optional argument for the number of charges:\\\verb=Ca\op[2]=  Ca\op[2], \verb=\phosphat\om[3]=  \phosphat\om[3].
+\end{itemize}
+
+\subsubsection{Stereo descriptors}\label{sssec:stereo}
+Some descriptors to make it easier writing the correct IUPAC name:
+\begin{itemize}
+ \item \verb=\Rcip= and \verb=\Scip=, rectus and sinister: \Rcip\ \Scip
+ \item \verb=\Dfi= and \verb=\Lfi=, dexter and laevus: \Dfi\ \Lfi
+ \item \verb=\E= and \verb=\Z=, opposite (german: entgegen) and together (german: zusammen): \E\ \Z
+ \item \verb=\rconf= and \verb=\sconf= R/S configuration: \rconf\ and \sconf. Both commands have an optional argument changing the letter: \verb=\rconf[] \sconf[A]= \rconf[] \sconf[A]
+\end{itemize}
+\subsubsection{Anions}
+I don't use them anymore since I found the `mhchem' package, but they're defined anyway:
+\begin{itemize}
+ \item \verb=\nitrat= : \nitrat
+ \item \verb=\nitrit= : \nitrit
+ \item \verb=\sulfat= : \sulfat
+ \item \verb=\sulfit= : \sulfit
+ \item \verb=\phosphat= : \phosphat
+ \item \verb=\phosphit= : \phosphit
+ \item \verb=\carbonat= : \carbonat
+\end{itemize}
+
+\subsubsection{Compatibility with `mhchem'}
+You can use all chemistry commands in the formula commands of the `mhchem' package\footnote{by Martin Hensel \url{http://www.ctan.org/tex-archive/macros/latex/contrib/mhchem/}} like \verb=\ce{}=. `mhchem' is loaded automatically by \CEx if it is installed. If you want to load `mhchem' with other options than \verb+version=3+ you need to load it seperately \emph{before} loading \CEx.
+\begin{lstlisting}[numbers=none,basicstyle=\normalsize\ttfamily,showspaces=true]
+ \ce{2|| ||\ox{0}{Ca} +|| ||\ox{0}{O}_2 ->T[{~~~REDOX~~~}] 2Ca|| ||\op[2] + 2O|| ||\om[2]}
+\end{lstlisting}
+\ce{ 2 \ox{0}{Ca} + \ox{0}{O}_2 ->T[{~~~REDOX~~~}] 2Ca \op[2] + 2O \om[2] }\\
+Please keep in mind that you need to leave the blanks before \verb=\om=, \verb=\op=, \verb=\ox{}{}=. Else you might get unexpected results:\verb=\ce{Ca\op[2]}=  \ce{ Ca\op[2] }.
+
+\noindent Some more examples:
+\begin{lstlisting}[numbers=none,basicstyle=\normalsize\ttfamily]
+ \begin{align*}
+  \cee{Na                  &->T[ox] Na\op||{}|| + \el}\\
+  \cee{HCl_{aq}            &<=>> H\op_{aq} + Cl\om_{aq}}\\
+  \cee{H2O                 &<<=> \Hpl + \Hyd}\\
+  \cee{CaCl2 + H2\sulfat||{}|| &-> Ca\sulfat||{}|| v + 2 HCl}
+ \end{align*}
+\end{lstlisting}
+\begin{align*}
+ \cee{Na                  &->T[ox] Na\op{} + \el}\\
+ \cee{HCl_{aq}            &<=>> H\op_{aq} + Cl\om_{aq}}\\
+ \cee{H2O                 &<<=> \Hpl + \Hyd}\\
+ \cee{CaCl2 + H2\sulfat{} &-> Ca\sulfat{} v + 2 HCl}
+\end{align*}
+
+\subsubsection{Commands for `mhchem'}
+\CEx also provides some commands for numbered and centered reactions created by `mh\-chem'.
+\begin{lstlisting}
+ Reaction with a number:
+ \reaction{2 H2 + O2 -> 2 H2O}%
+ Reaction without a number:
+ \reaction*{2 CO + O2 -> 2 CO2}
+ More reactions at once, aligned:
+ \reactions{Cl_2 ||&||-> 2 Cl. ||\\|| Cl. + CH4 ||&||-> HCl + {}.CH3}
+\end{lstlisting}
+Reaction with a number:
+\reaction{2 H2 + O2 -> 2 H2O}%
+Reaction without a number:
+\reaction*{2 CO + O2 -> 2 CO2}
+More reactions at once, aligned:
+\reactions{Cl2 &-> 2 Cl. \\ Cl. + CH4 &-> HCl + {}.CH3}
+
+\section{New environments}
+\subsection{The {\ttfamily beispiel} environment - creating examples}\label{ssec:beispiele}
+The \verb=beispiel= environment is an environment for examples. Examples automatically are numbered and placed between two lines. The fontsize of the examples is \verb=\small=.
+\begin{lstlisting}
+ ||\begin{beispiel}||
+  an example
+ ||\end{beispiel}||
+\end{lstlisting}
+\begin{beispiel}
+ an example
+\end{beispiel}
+\noindent If you want to give two or more examples in between the same two lines, you can use \verb=\bsp=:
+\begin{lstlisting}
+ \begin{beispiel}
+  first example
+  ||\bsp||
+  second one
+ \end{beispiel}
+\end{lstlisting}
+\begin{beispiel}
+ first example
+ \bsp
+ second one
+\end{beispiel}
+
+\subsubsection{The options \texttt{color}, \texttt{linecolor} \&\ \texttt{english}}
+The \verb+linecolor=<color>+ option changes the color of the lines:
+\begin{lstlisting}
+ % preamble:
+ \usepackage||[linecolor={rgb:red,4;green,6}]||{chemexec}
+ % in the document:
+ \begin{beispiel}
+  green lines through package option
+ \end{beispiel}
+\end{lstlisting}
+folgenden Output:
+\begin{beispiel}[linecolor={rgb:red,4;green,6}]
+ green lines through package option
+\end{beispiel}
+\noindent The option \verb+color=<color>+ also changes the color of the lines (but also changes the color of other things,too).\\
+By using the key \verb+linecolor=<color>+ you can change the color of a single example:
+\begin{lstlisting}
+ \begin{beispiel}||[linecolor=purple]||
+  the lonely purple one
+ \end{beispiel}
+\end{lstlisting}
+folgenden Output:
+\begin{beispiel}[linecolor=purple]
+ the lonely purple one
+\end{beispiel}
+\noindent The \verb=english= option translates "Beispiel" into "Example".
+
+\subsubsection{Not numbered examples}
+If you don't like the numbering you can redefine the counter as usual.
+\begin{lstlisting}
+ \renewcommand{\thebeispiel}{}
+ \begin{beispiel}
+  now without counter
+ \end{beispiel}
+\end{lstlisting}
+\renewcommand{\thebeispiel}{}
+\begin{beispiel}
+ now without counter
+\end{beispiel}
+\begin{lstlisting}
+ \renewcommand{\thebeispiel}{\alph{beispiel})}
+ \begin{beispiel}
+  or alphabetically \ldots
+ \end{beispiel}
+\end{lstlisting}
+\renewcommand{\thebeispiel}{\alph{beispiel})}
+\begin{beispiel}
+ or alphabetically \ldots
+\end{beispiel}
+
+\subsection{The {\ttfamily definition} environment}\label{sec:definition}
+The \verb=definition= environment creates a box with a colored title:
+\begin{lstlisting}
+ ||\begin{definition}||
+  The absolut value of a vector in $\mathbb{R}^3$ is
+  \begin{equation}
+   ||\abs{\vek{||a||}}||=\sqrt{a_x^2+a_y^2+a_z^2}
+  \end{equation}
+ ||\end{definition}||
+\end{lstlisting}
+\begin{definition}
+ The absolut value of a vector in $\mathbb{R}^3$ is
+ \begin{equation}
+  \abs{\vek{a}}=\sqrt{a_x^2+a_y^2+a_z^2}
+ \end{equation}
+\end{definition}
+
+\subsubsection{The options \texttt{shade}, \texttt{shadecolor} \& \texttt{color}}
+With the key \verb+shade=<boolean>+ you can change the layout:
+\begin{lstlisting}
+ \begin{definition}||[shade=true]||
+  The absolut value of a vector in $\mathbb{R}^3$ is
+  \begin{equation}
+   \abs{\vek{a}}=\sqrt{a_x^2+a_y^2+a_z^2}
+  \end{equation}
+ \end{definition}
+\end{lstlisting}
+\begin{definition}[shade=true]
+ The absolut value of a vector in $\mathbb{R}^3$ is:
+ \begin{equation}
+  \abs{\vek{a}}=\sqrt{a_x^2+a_y^2+a_z^2}
+ \end{equation}
+\end{definition}
+By using the keys \verb+shadecolor=<color>+ und \verb+color=<color>+ you can customize the environment:
+\begin{lstlisting}
+ \begin{definition}||[shade=true,shadecolor=green!15,color=black]||
+  The absolut value of a vector in $\mathbb{R}^3$ is
+  \begin{equation}
+   \abs{\vek{a}}=\sqrt{a_x^2+a_y^2+a_z^2}
+  \end{equation}
+ \end{definition}
+\end{lstlisting}
+\begin{definition}[shade=true,shadecolor=green!15,color=black]
+ The absolut value of a vector in $\mathbb{R}^3$ is:
+ \begin{equation}
+  \abs{\vek{a}}=\sqrt{a_x^2+a_y^2+a_z^2}
+ \end{equation}
+\end{definition}
+You can use all of these keys as package options as well. This way, you can change the layout of every \verb=definition= environment at once. Please keep in mind, that in this case \verb+color=<color>+ also has effects on other commands and environments.
+\begin{lstlisting}
+ % preamble:
+ \usepackage||[shade=true,shadecolor=yellow!15]||{chemexec}
+ % in the document:
+ \begin{definition}
+  The absolut value of a vector in $\mathbb{R}^3$ is
+  \begin{equation}
+   \abs{\vek{a}}=\sqrt{a_x^2+a_y^2+a_z^2}
+  \end{equation}
+ \end{definition}
+\end{lstlisting}
+\begin{definition}[shade=true,shadecolor=yellow!15]
+ The absolut value of a vector in $\mathbb{R}^3$ is:
+ \begin{equation}
+  \abs{\vek{a}}=\sqrt{a_x^2+a_y^2+a_z^2}
+ \end{equation}
+\end{definition}
+
+\subsubsection{The \texttt{defformel} environment}
+There is an additional environment, which only creates a white box. It has an optional argument for the width of the box.
+\begin{lstlisting}
+ \begin{definition}[shade=true]
+  A carbon atom with four different substituents is called \textbf{asymmetric}. Asymmetric carbon atoms often are labelled with a \textasteriskcentered.
+  ||\begin{defformel}[.5\textwidth]||
+   \setatomsep{1.8em}
+   \chemfig{R_1-[:30](-[2]R|_2)(-[6]R|_3)(-[:30,.15,,,white]{\text{\textasteriskcentered}})-[:-30]R_4}
+  ||\end{defformel}||
+ \end{definition}
+\end{lstlisting}
+
+\begin{definition}[shade=true]
+  A carbon atom with four different substituents is called \textbf{asymmetric}. Asymmetric carbon atoms often are labelled with a \textasteriskcentered.
+  \begin{defformel}[.5\textwidth]
+   \setatomsep{1.8em}
+   \chemfig{R_1-[:30](-[2]R|_2)(-[6]R|_3)(-[:30,.15,,,white]{\text{\stec}})-[:-30]R_4}
+  \end{defformel}
+ \end{definition}
+
+\subsection{The \texttt{exkurs} environment}
+The \verb=exkurs= environment is used to visually highlight an excursus (in a book or longer text) and produce an entry in the table of contents.
+\begin{lstlisting}[numbers=none,basicstyle=\normalsize\ttfamily]
+ \begin{exkurs}[options]{title}
+  ...
+ \end{exkurs}
+\end{lstlisting}
+You have two options: the \verb+toc=<toclevel>+ option with \verb=section= as default and the\linebreak\verb+color=<color>+ option.
+\begin{lstlisting}
+ ||\begin{exkurs}[color=-yellow]{Lorem ipsum}||
+  Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. ...
+ ||\end{exkurs}||
+\end{lstlisting}
+\begin{exkurs}[color=-yellow,toc=paragraph]{Lorem ipsum}
+ Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zuril delenit augue duis dolore te feugait nulla facilisi.
+\end{exkurs}
+If you use \verb+color=<color>+ it also chages the color in other environments. The package option \verb=english= changes the german caption "Exkurs" into "Excursus".
+
+\section[Exercises/solutions]{The option \texttt{exercise}: numbered exercises/solutions}\label{sec:aufgaben}
+The main part of \CEx provides the commands for exercises and their solutions, which can be activated by the package option \verb=exercise=. Exercises have "Aufgabe" or "Exercise", respectively, as default title, which can be changed with the argument.
+\begin{lstlisting}[numbers=none,basicstyle=\normalsize\ttfamily]
+ \aufgabe{<title>}
+\end{lstlisting}
+For creating the solutions to the exercises, there are three commands:
+\begin{lstlisting}[numbers=none,basicstyle=\normalsize\ttfamily]
+ \loesung[<title>]{<solution>} % remember the solution
+ \doloesung % writing the solutions sectionwise
+ \makeloesung % writing all solutions
+\end{lstlisting}
+The first command \verb=\loesung{}= is used, to write the solution of an exercise \emph{directly after the exercise}. The second command \verb=\doloesung= writes all the solutions gathered in the actual \verb=section= by the \verb=\loesung{}= commands. Since sections reset the counter of the exercises and \verb=\doloesung= resets gathering of the solutions, you should use \verb=\doloesung= at the end of a section. Otherwise, the numbers of the solutions might not be the numbers of the corresponding exercises anymore. If you're creating a document which has chapters, you should keep in mind, that \verb=\doloesung= should be used at the end of a chapter, if you had exercises in that chapter.\\
+Instead of \verb=\doloesung=, you can use \verb=\makeloesung= once after \emph{all} exercises and solutions are set to write all the solutions.
+
+\subsection{Options}
+With the \verb+exersize=<fontsize>+ option you can change the fontsize of the exercises' and solutions' titles. Possible values are the usual ones: \verb=tiny=, \verb=scriptsize=, \verb=footnotesize=, \verb=small=, \verb=normalsize=, \verb=large=, \verb=Large=, \verb=LARGE=, \verb=huge= and \verb=Huge=.\\
+Default font size is \verb=normalsize=.\\
+The \verb+numcolor=<color>+ package option changes the color of the numbers with which the exercises are numbered. The \verb=english= package option translates "Aufgabe" into "Exercise" and "L\"osung" into "Solution".\\
+In the default behaviour \CEx resets the numbers of the exercises with each new \verb=\section=. If you use the \verb=chapter= package option, the counter is reset with each new \verb=\chapter=.
+
+\subsection{The {\ttfamily alphlist} environment}
+The \texttt{alphlist} environment creates a list similar to the \verb=enumerate= environment, but counts the items with a), b) etc.
+\begin{lstlisting}
+ \begin{alphlist}
+  \item first item
+  \item second item
+ \end{alphlist}
+\end{lstlisting}
+\begin{alphlist}
+ \item first item
+ \item second item
+\end{alphlist}
+
+\subsection{Example}
+In the following example you see the \verb=\aufgabe=, \verb=\loesung= and \verb=doloesung= commands in action.
+\begin{lstlisting}
+ % preamble:
+ \usepackage||[exercise,exersize=large]||{chemexec}
+ % Im Dokument:
+ \par{\Large\bfseries\noindent Exercises}
+ ||\aufgabe{}||
+  Write down the protolysis reactions of phosphoric acid.||\loesung{||\ce{H3PO4 <=> \Hpl{} + H2PO4\om{} <=> 2\Hpl{} + HPO4 \om[2]{} <=> 3\Hpl{} + PO4 \om[3]}||}||
+ ||\aufgabe{||Oxidation states||}||
+  Which oxidation state has nitrogen in thze following compounds: ammonia, nitric oxide, nitrogen dioxide, nitric acid?||\loesung[||Oxidation states||]{||
+  \ce{ \ox{-3}{N} H3}, \ce{ \ox{+2}{N} O}, \ce{ \ox{+4}{N} O2}, \ce{H \ox{+5}{N} O3}||}||
+ ||\aufgabe{||Nomenclature||}||
+  Name the molecules:\\\setatomsep{1.4em}
+  \begin{inparaenum}[a)]
+   \item\chemfig{-[::30](=[::60]O)-[::-60]OH}
+   \item\chemfig{-[::30](=[::60]O)-[::-60]O-[::60]-[::-60]}
+   \item\chemfig{HO-[::-30](=[::-60]O)-[::60]-[::-60]-[::60](=[::60]O)-[::-60]OH}
+  \end{inparaenum}
+ ||\loesung[||Nomenclature||]{||
+  \begin{inparaenum}[a)]
+   \item ethanoic acid
+   \item ethyl ethanoate
+   \item butanedioic acid
+  \end{inparaenum}
+ ||}||
+ ||\aufgabe{}||
+  Sketch the skeletal formula of glycerol. Also give the IUPAC name.
+ ||\loesung{\chemname{\chemfig{HO-[::-30]-[::60](-[::60]OH)-[::-60]-[::60]OH}}{1,2,3-Propantriol}}||
+ \vspace{\baselineskip}
+ \par{\Large\bfseries\noindent Solutions}
+ ||\doloesung||
+\end{lstlisting}
+\newpage
+\par{\Large\bfseries\noindent Exercises}
+\aufgabe{}
+ Write down the protolysis reactions of phosphoric acid.\loesung{\ce{H3PO4 <=> \Hpl{} + H2PO4\om{} <=> 2\Hpl{} + HPO4 \om[2]{} <=> 3\Hpl{} + PO4 \om[3]}}
+\aufgabe{Oxidation states}
+ Which oxidation state has nitrogen in thze following compounds: ammonia, nitric oxide, nitrogen dioxide, nitric acid?\loesung[Oxidation states]{\ce{ \ox{-3}{N} H3}, \ce{ \ox{+2}{N} O}, \ce{ \ox{+4}{N} O2}, \ce{H \ox{+5}{N} O3}}
+\aufgabe{Nomenclature}
+ Name the molecules:\\\setatomsep{1.4em}
+ \begin{inparaenum}[a)]
+  \item\chemfig{-[::30](=[::60]O)-[::-60]OH} \item \chemfig{-[::30](=[::60]O)-[::-60]O-[::60]-[::-60]} \item \chemfig{HO-[::-30](=[::-60]O)-[::60]-[::-60]-[::60](=[::60]O)-[::-60]OH}
+ \end{inparaenum}
+ \loesung[Nomenclature]{
+ \begin{inparaenum}[a)]
+ \item ethanoic acid
+ \item ethyl ethanoate
+ \item butanedioic acid
+ \end{inparaenum}
+}
+\aufgabe{}
+ Sketch the skeletal formula of glycerol. Also give the IUPAC name.
+\loesung{\chemname{\chemfig{HO-[::-30]-[::60](-[::60]OH)-[::-60]-[::60]OH}}{propan-1,2,3-triol}}
+\vspace{\baselineskip}
+\par{\Large\bfseries\noindent Solutions}
+\doloesung
+
+\subsection{Bugs?}
+It is very likely, that either \verb=\doloesung= or \verb=\makeloesung= or both have bugs. If you detect any, please let me know.
+
+\section{Replacement for \texttt{echem.sty}}
+The \verb=echem.sty= is part of Ingo Kl\"ockls OCHEM\footnote{\url{http://tug.ctan.org/tex-archive/support/ochem/}}. It enables the lewis representation of electrons. Additionally \verb=echem.sty= provides the commands \verb=\sbond= und \verb=\dbond= with which you can typeset a single or a double bond in normal text. Both commands are defined in the `mhchem' package as well-
+\begin{itemize}
+ \item `mhchem':
+ \begin{itemize}
+  \item\texttt{\textbackslash ce\{F\textbackslash sbond F\}}: \ce{F\sbond F}
+  \item\texttt{\textbackslash ce\{O\textbackslash dbond O\}}: \ce{O\dbond O}
+ \end{itemize}
+ \item\newcommand{\sibond}{\,\ensuremath{\cdot}\,}\newcommand{\dobond}{\,=\,} `echem':
+ \begin{itemize}
+  \item\texttt{F\textbackslash sbond F}: F\sibond F
+  \item\texttt{O\textbackslash dbond O}: O\dobond O
+ \end{itemize}
+\end{itemize}
+To avoid conflicts with `mhchem' besides these two commands and the commands \verb=\2= and \verb=\3= \CEx has the same functionality as \verb=echem.sty=. So it can be used instead of \verb=echem.sty= in OCHEM's \verb=chemspecial= environment.
+\begin{lstlisting}
+ % preamble
+ \usepackage{ochem,chemexec}
+ % in the document:
+ \begin{chemspecial}
+  ||package("chemexec")||
+ \end{chemspecial}
+ \begin{chemistry}
+  formula(L,R){
+    bond(30;-30;30)
+    branch { bond(90,=C)
+             atom("||\vdd{||O||}||O\vdd{O}");
+           }
+    bond(-30;30;-30)
+    atom("||\hdl[\echhbar]{||O||}\hdu||[\echhbar]||{||O||}||O",L,R)
+    bond(30;-30)
+  }
+ \end{chemistry}
+\end{lstlisting}
+\includegraphics{./formel.jpg}%\\% formel.jpg: 131x44 pixel, 100dpi, 3.33x1.12 cm, bb=0 0 94 32
+
+\section{Epilogue}
+I tried using real chemical reactions but I didn't make sure, that they all make sense chemically. So you shouldn't trust the examples in respect to chemistry but rather take a look into a real chemistry teaching book.\\
+I apologize for any bad or wrong English. I hope you understood the documention anyway.
+\end{document}
\ No newline at end of file
diff --git a/Master/texmf-dist/tex/latex/chemexec/chemexec.sty b/Master/texmf-dist/tex/latex/chemexec/chemexec.sty
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@@ -0,0 +1,1033 @@
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% ------------------------------------------------------------------------------------- %
+% - chemexec - chemexec.sty ----------------------------------------------------------- %
+% - creating (chemical) exercise sheets, chemical macros ------------------------------ %
+% ------------------------------------------------------------------------------------- %
+% - Clemens Niederberger -------------------------------------------------------------- %
+% - 2011/03/06 ------------------------------------------------------------------------ %
+% ------------------------------------------------------------------------------------- %
+% - http://www.niederberger-berlin.net/2010/08/latex-chemische-formeln-erstellen-iiv/ - %
+% - kontakt@niederberger-berlin.net --------------------------------------------------- %
+% ------------------------------------------------------------------------------------- %
+% - If you have any ideas, questions, suggestions or bugs to report, please feel free - %
+% - to contact me. -------------------------------------------------------------------- %
+% ------------------------------------------------------------------------------------- %
+% Copyright 2011 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.                          %
+%                                                                                       %
+% This work consists of the files chemexec.sty, chemexec_de.tex                         %
+% and chemexec_en.tex                                                                   %
+% ------------------------------------------------------------------------------------- %
+% 27. April 2009 Version 0.1
+%   `chemexec' ist zun"achst als eine lose Makrosammlung entstanden
+%   und stellt einige kleinere Umgebungen und Befehle zur Verf"ugung,
+%   die das Arbeiten mit Chemischen und mathematischen Formeln
+%   erleichtern sollen.
+%   Zentrales anliegen war ein komfortabler Umgang mit Aufgaben
+%   und L"osungen vor allem f"ur das Erstellen von "Ubungsbl"attern
+%   und den Einsatz in Lehrb"uchern u."a.
+%
+% 29. Oktober 2009 Version 0.2
+%   `chemexec' hat viele neue Optionen erhalten, einige Makros sind
+%   hinzugekommen. Ausserdem wurden einige Fehler berichtigt und der
+%   Code vereinheitlicht.
+%
+% "Anderungen:
+% 19. Oktober 2009 Version 0.3
+%    - Inkonsistenzen bei Aufgaben/L"osungen/Schemas bereinigt.
+%    - definition-Umgebung neu definiert, dass das Leerzeichen hinter der Umgebung
+%      verschwindet und sie flexibel gestalte werden kann (s.u.).
+%   Neue Features:
+%    - Option `chapter':
+%      Aufgaben, L"osungen und Schema-Umgebung werden damit chapter-weise
+%      statt section-weise durchnummeriert.
+%    - Option `shade':
+%      definition-Umgebung wird damit nicht umrahmt, sondern hellrosa
+%      unterlegt.
+%      -> neue Umgebung `defformula'
+%    - Option `here':
+%      Schema-Umgebung wird mit `H' positioniert.
+%    - chem. Kleinigkeiten:
+%      Stereo-Deskriptoren
+%    - Extras f"ur `ochem':
+%      verschiedene Makros durch package("chemexec") f"ur `ochem' (bzw. `ochemcol')
+%      verf"ugbar machen
+% 24. Oktober 2009 Version 0.4
+%    - Paketoptionen "uberarbeit, Optionen mit xkeyval setzen, eine Reihe
+%      weiterer Optionen:
+%      flexible Gestaltung der Definition- und Beispiel-Umgebung, der Aufgaben/
+%      L"osungen
+% 25. Oktober 2009 Version 0.4b
+%    - Bugfix: Option shade hat framed-Umgebung umdefiniert -- gel"ost
+%    - Bugfix: wenn die Klasse report o. book gew"ahlt war, konnte \makeloesung
+%      nur zusammen mit der Option `chapter' verwendet werden -- gel"ost
+%    - Kleinere "Anderungen an \makeloesung
+%    - NEU: \lewisbar{}{} und die Exkurs-Umgebung
+% 27. Oktober 2009 Version 0.4c
+%    - Bugfix: fehlerhafter Hyperlink bei Exkurs-Umgebung wenn hyperref-
+%      Paket verwendet wird -- gel"ost.
+%    - L"ange der Exkurs-Linien an \textwidth anpassen
+%    - Benennung interner Makros und Zaehler vereinheitlicht, durch @-Character
+%      interne Verwendung sichergestellt
+% 28. Oktober 2009 Version 0.4d
+%    - Kompatibilit"at der lewis, lewisbar und ox-Befehle mit Martin Hensels `mhchem'
+%      Paket. Befehle sind nun innerhalb \ce{} einsetzbar.
+%    - Befehle \om und \op hinzugef"ugt.
+%    - Befehle \ronf und \sconf f"ur Einatz im Fließtext verbessert. Um optionales
+%      Argument erweitert.
+%    - Erscheinungsbild der lewis-Befehle verbessert.
+%    - Kleinigkeiten am Erscheinungsbild der Beispiele ge"andert.
+% 29. Oktober 2009 Version 0.4e
+%    - S"aurereste `mhchem'-tauglich gemacht
+%    - atomconnect modifiziert
+% 24. Januar 2010 Version 0.5
+%    - Listenumgebung `alphlist' hinzugef"ugt
+% 11. Februar 2010 Version 0.5a
+%    - Die Befehle lewis u. lewisbar flexibilisiert.
+% 18. Februar 2010 Version 0.5b
+%    - \reaction und \reactions hinzugef"ugt
+% 09. September 2010 Version 0.5c
+%    - Befehle \lewis und \lewisbar in \lw und \lwbar umbenannt, um Kompatibilit"at mit
+%      `chemfig' zu gewährleisten
+% 01. M"arz 2011 Version 0.6
+%    - Bugfix in der Beispiel-Umgebung
+% 06. M"arz 2011 Version 1.0
+%    - atomconnect entfernt
+%    - exkurs-Umgebung auf tikz umgestellt
+%    - \rconf u. \sconf auf tikz umgestellt
+%    - \auge auf tikz umgestellt
+%    - lw/lwbar entfernt (Lewisformeln k"onnen mit ChemFig realisiert werden.)
+%    - Schema-Umgebung entfernt
+%    - Option `here' entfernt
+% ------------------------------------------------------------------------------------- %
+% TODO:
+%    - bug bei \reaction: whitespace nach nummerierter Reaktion
+%    - doloesung Option für section-weises bzw. chapter-weises sammeln geben
+%    - doloesung und makeloesung nochmal auf Herz und Nieren pr"ufen
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\NeedsTeXFormat{LaTeX2e}
+\def\ce@version{v1.0}
+\def\ce@date@de{06. M\"arz 2011}
+\def\ce@date@en{March 06. 2011}
+\providecommand{\CEversion}{\ce@version}
+\providecommand{\CEdate}[1]{
+  \ifthenelse{\equal{#1}{de}}{\ce@date@de}{}
+  \ifthenelse{\equal{#1}{en}}{\ce@date@en}{}
+}
+\ProvidesPackage{chemexec}[2011/03/01]
+\typeout{CHEMEXEC \ce@version}
+\typeout{2011/03/01 Clemens Niederberger}
+\typeout{Customizing your (chemical) exercise sheets.}
+\typeout{}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - Optionen -------------------------------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - Pakete ---------------------------------------------------------------------------- %
+\RequirePackage{calc}
+\RequirePackage{amsmath}
+\RequirePackage{ifthen}
+\RequirePackage{accents}
+\RequirePackage{framed}
+\RequirePackage{xcolor}
+\RequirePackage{xkeyval}
+\RequirePackage{tikz}
+  \usetikzlibrary{calc}
+% - interne Befehle --------------------------------------------------------- %
+\newcommand{\@aufgabe@name}{Aufgabe}
+\newcommand{\@aufgabe@groesse}{normalsize}
+\newcommand{\@loesung@titel}{L\"osung}
+\newcommand{\@beispiel@name}{Beispiel}
+\newcommand{\@exkurs@name}{EXKURS}
+\newcommand{\@exkurs@toc}{section}
+\newcommand{\@exkurs@currenttoc}{\@exkurs@toc}
+\newcommand{\@exkurs@color}{dunkelblau}
+\newcommand{\@exkurs@currentcolor}{\@exkurs@color}
+\xdefinecolor{dunkelblau}{rgb}{0,0.33,0.62}
+\xdefinecolor{dunkelrot}{rgb}{0.4392,0.0627,0.0627}
+\newcommand{\@definition@shadecolor}{pink!50}
+\newcommand{\@definition@color}{dunkelblau}
+\newcommand{\@definition@currentshadecolor}{\@definition@shadecolor}%
+\newcommand{\@definition@currentcolor}{}%
+\newcommand{\@bsprule@linecolor}{dunkelblau}
+\newcommand{\@numbers@numcolor}{dunkelblau}
+% - Bedingungen ------------------------------------------------------------ %
+\newif\if@useaufg\@useaufgfalse
+\newif\if@usechapter\@usechapterfalse
+%\newif\if@usehere\@useherefalse
+\newif\if@shaded
+% - Optionen --------------------------------------------------------------- %
+\DeclareOptionX[CE]{exercise}{\@useaufgtrue}
+\DeclareOptionX[CE]{chapter}{\@usechaptertrue}
+%\DeclareOptionX[CE]{here}{\@useheretrue}
+\DeclareOptionX[CE]{english}{
+  \renewcommand\@aufgabe@name{Exercise}
+  \renewcommand\@loesung@titel{Solution}
+  \renewcommand{\@beispiel@name}{Example}
+  \renewcommand{\@exkurs@name}{EXCURSUS}
+}
+\define@key[CE]{chemexec.sty}%
+    {color}{
+        \renewcommand{\@bsprule@linecolor}{#1}
+        \renewcommand{\@definition@color}{#1}
+        \renewcommand{\@numbers@numcolor}{#1}
+        \renewcommand{\@exkurs@color}{#1}
+    }
+\define@key[CE]{chemexec.sty}%
+    {exersize}{
+        \renewcommand{\@aufgabe@groesse}{#1}
+    }
+\define@key[CE]{chemexec.sty}%
+    {numcolor}{
+        \renewcommand{\@numbers@numcolor}{#1}
+    }
+\define@key[CE]{chemexec.sty}%
+    {shadecolor}{
+        \renewcommand{\@definition@shadecolor}{#1}
+    }
+\define@key[CE]{chemexec.sty}%
+    {linecolor}{
+        \renewcommand{\@bsprule@linecolor}{#1}
+    }
+\define@boolkey+[CE]{chemexec.sty}[CE@]{shade}{%
+  \ifCE@shade
+    \@shadedtrue
+  \else
+    \@shadedfalse
+  \fi
+}{
+  \PackageWarning{chemexec}{Option `shade' is not boolean!}%
+}
+
+\ProcessOptionsX[CE]
+
+\IfFileExists{ulem.sty}{%
+  \RequirePackage[normalem]{ulem}
+  \providecommand*{\unterstr}[1]{\uline{##1}}%
+}{%
+  \providecommand*{\unterstr}[1]{##1}%
+}
+\IfFileExists{mhchem.sty}{%
+  \RequirePackage[version=3]{mhchem}
+}{%
+  \typeout{`mhchem' ist nicht installiert. Manche Befehle werden nicht definiert.}
+}
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - Vektoren & math. Kleinigkeiten ---------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% Vektoren
+\providecommand{\vek}[1]{ \ensuremath{ \accentset{\rightarrow}{#1} } }              % Pfeildarstellung
+\providecommand{\vekzw}[2]{ \ensuremath{ \begin{pmatrix}#1\\#2\end{pmatrix} } }     % 2er Spaltenvektor
+\providecommand{\vekdr}[3]{ \ensuremath{ \begin{pmatrix}#1\\#2\\#3\end{pmatrix} } } % 3er Spaltenvektor
+\providecommand\abs[1]{\ensuremath{\left\lvert#1\right\rvert}}                      % Betrag
+% Operatoren
+\DeclareMathOperator\arccot{arccot} % Arcuscotangens
+\DeclareMathOperator\arsinh{arsinh} % area sinus hyperbolicus
+\DeclareMathOperator\arcosh{arcosh} % area cosinus hyperbolicus
+\DeclareMathOperator\artanh{artanh} % area tangengs hyperbolicus
+\DeclareMathOperator\arcoth{arcoth} % area cotangens hyperbolicus
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - chem. Kleinigkeiten --------------------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\providecommand\el{\ensuremath{e^\ominus}}                    % Elektronen
+\providecommand\prt{\ensuremath{p^\oplus}}                    % Protonen
+\providecommand\ntr{\ensuremath{n^0}}                         % Neutronen
+\providecommand{\om}[1][]{\ensuremath{{}^{#1\ominus}}}        % negative Ladung
+\providecommand{\op}[1][]{\ensuremath{{}^{#1\oplus}}}         % positive Ladung
+\providecommand\Rcip{\textit{(R)}}                            % stereo-Deskriptor
+\providecommand\Scip{\textit{(S)}}                            %   "
+\providecommand\E{\textit{(E)}}                               %   "
+\providecommand\Z{\textit{(Z)}}                               %   "
+\providecommand\Dfi{\textsc{d}}                               %   "
+\providecommand\Lfi{\textsc{l}}                               %   "
+
+\providecommand\sconf[1][S]{%                                       % S-Konfiguration
+  \tikz[baseline=(a.base),text height=1.5ex,text depth=.25ex]{\draw  node(a) at (0,0) {#1};\draw[->,thick,rotate=90] (20:.3cm) arc (20:340:.3cm);}
+}
+\providecommand\rconf[1][R]{%                                       % R-Konfiguration
+  \tikz[baseline=(a.base),text height=1.5ex,text depth=.25ex]{\draw  node(a) at (0,0) {#1};\draw[<-,thick,rotate=90] (20:.3cm) arc (20:340:.3cm);}
+}
+
+\IfFileExists{mhchem.sty}{%
+\newcounter{save}%
+\if@usechapter%
+\newcounter{reaction}[chapter]%
+\renewcommand\thereaction{R\,\thechapter.\arabic{equation}}%
+\else%
+\newcounter{reaction}%
+\renewcommand\thereaction{R\,\arabic{equation}}%
+\fi
+
+\long\def\react@##1{%
+\setcounter{save}{\value{equation}}\setcounter{equation}{\value{reaction}}\def\theequation{\thereaction}%
+\begin{equation}\ce{##1}\end{equation}%
+\setcounter{reaction}{\value{equation}}\setcounter{equation}{\value{save}}\def\theequation{\arabic{equation}}%
+}
+
+\long\def\react@nonumber##1{\begin{equation*}\ce{##1}\end{equation*}}
+
+\providecommand\reaction{\@ifstar{\react@nonumber}{\react@}}
+
+\long\def\rctns@##1{%
+\setcounter{save}{\value{equation}}\setcounter{equation}{\value{reaction}}\def\theequation{\thereaction}%
+\begin{align}\cee{##1}\end{align}%
+\setcounter{reaction}{\value{equation}}\setcounter{equation}{\value{save}}\def\theequation{\arabic{equation}}%
+}
+\long\def\rctns@nonumber##1{%
+\begin{align*}\cee{##1}\end{align*}%
+}
+\providecommand\reactions{\@ifstar{\rctns@nonumber}{\rctns@}}
+}{}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - extras f"ur `ochem' --------------------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\providecommand\stec{\textasteriskcentered}                   % opt. aktives Zentrum (f"ur ochem)
+\providecommand{\auge}{%                                      % Bild eines Auges (f"ur ochem)
+\tikz{\draw (0,0)--(20:7mm);\draw (0,0)--(-20:7mm);\fill (0,0) -- (-20:2.5mm) arc (-20:20:2.5mm);\draw (-20:6.5mm) arc (-20:20:6.5mm);}
+}
+
+%% FOLGENDER CODE WURDE AUS ECHEM.STY VON INGO KL"OCKL "UBERNOMMEN UND TEILWEISE
+%% ANGEPASST
+% Symbol fuer einzelnes Elektron
+\newcommand{\@el}
+{{\unitlength=.12\baselineskip%
+  \begin{picture}(0,0)
+    \put(0,0){\circle*{1.2}}
+  \end{picture}}}
+% liegender Balken fuer Elektronenpaar
+\newcommand{\@elpairh}
+{{\unitlength=.07\baselineskip%
+  \linethickness{0.5\unitlength}%
+  \begin{picture}(0,0)
+    \put(-3,0){\line(1,0){6}}
+  \end{picture}}}
+% aufrechter Balken fuer Elektronenpaar
+\newcommand{\@elpairv}
+{{\unitlength=.07\baselineskip%
+  \linethickness{0.5\unitlength}%
+  \begin{picture}(2,0)(-1,0)
+    \put(0,-3){\line(0,1){6}}
+  \end{picture}}}
+
+\providecommand{\echhbar}{\@elpairh}
+\providecommand{\echvbar}{\@elpairv}
+
+% die horizontalen Symbole (upper und lower)
+\newsavebox{\cbox}
+
+\providecommand{\hdu}[2][\@el]
+{\sbox{\cbox}{#2}%
+ \makebox[0pt][l]{\raisebox{1.35\ht\cbox}
+   {\makebox[\wd\cbox]{#1}}}%
+}
+\providecommand{\hddu}[1]
+{\sbox{\cbox}{#1}%
+ \makebox[0pt][l]{\raisebox{1.3\ht\cbox}
+   {\makebox[\wd\cbox]
+     {\@el\hspace*{0.6\ht\cbox}\@el}}}%
+}
+\providecommand{\hdl}[2][\@el]
+{\sbox{\cbox}{#2}%
+ \makebox[0pt][l]{\raisebox{-\dp\cbox-0.3\ht\cbox}
+   {\makebox[\wd\cbox]{#1}}}%
+}
+\providecommand{\hddl}[1]
+{\sbox{\cbox}{#1}%
+ \makebox[0pt][l]{\raisebox{-\dp\cbox-0.3\ht\cbox}
+   {\makebox[\wd\cbox]
+     {\@el\hspace*{0.6\ht\cbox}\@el}}}%
+}
+
+% die vertikalen Symbole
+\providecommand{\vd}[2][\@el]
+{\sbox{\cbox}{#2}\hspace*{0.1\ht\cbox}%
+ \raisebox{0.5\ht\cbox}{#1}%
+ \hspace*{0.1\ht\cbox}%
+}
+\providecommand{\vdd}[1]
+{\sbox{\cbox}{#1}\hspace*{0.2\ht\cbox}%
+ \makebox[0pt][l]{\raisebox{0.2\ht\cbox}{\@el}}%
+ \raisebox{0.8\ht\cbox}{\@el}%
+ \hspace*{0.23\ht\cbox}%
+}
+%% OBIGER CODE WURDE AUS ECHEM.STY VON INGO KL"OCKL "UBERNOMMEN UND TEILWEISE
+%% ANGEPASST.
+
+\IfFileExists{mhchem.sty}{
+\DeclareRobustCommand\Hpl{\cf{H$^\oplus$}}            % Protonen
+\DeclareRobustCommand\Hyd{\cf{OH$^\ominus$}}          % Hydroxid
+\DeclareRobustCommand\ox[2]{\ensuremath{\accentset{##1}{\cf{##2}}}}
+%\DeclareRobustCommand\lw[3][0]{
+%\ensuremath{
+%\ifcase ##3
+%\or%1
+% \ifcase ##1
+%  \vd{##2}\cf{##2}
+% \or
+%  \hdu{##2}\cf{##2}
+% \or
+%  \cf{##2}\vd{##2}
+% \or
+%  \hdl{##2}\cf{##2}
+% \else
+% \fi
+%\or%2
+% \ifcase ##1
+%  \vd{##2}\hdu{##2}\cf{##2}
+% \or
+%  \hdu{##2}\cf{##2}\vd{##2}
+% \or
+%  \hdl{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd{##2}\hdl{##2}\cf{##2}
+% \or
+%  \vd{##2}\cf{##2}\vd{##2}
+% \or
+%  \hdu{##2}\hdl{##2}\cf{##2}
+% \else
+% \fi
+%\or%3
+% \ifcase ##1
+%  \vd{##2}\hdu{##2}\cf{##2}\vd{##2}
+% \or
+%  \hdu{##2}\hdl{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd{##2}\hdl{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd{##2}\hdu{##2}\hdl{##2}\cf{##2}
+% \else
+% \fi
+%\or%4
+% \vd{##2}\hdu{##2}\hdl{##2}\cf{##2}\vd{##2}
+%\or%5
+% \ifcase ##1
+%  \vd{##2}\hddu{##2}\hdl{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd{##2}\hdu{##2}\hdl{##2}\cf{##2}\vdd{##2}
+% \or
+%  \vd{##2}\hddl{##2}\hdu{##2}\cf{##2}\vd{##2}
+% \or
+%  \vdd{##2}\hdu{##2}\hdl{##2}\cf{##2}\vd{##2}
+% \else
+% \fi
+%\or%6
+% \ifcase ##1
+%  \vdd{##2}\hddu{##2}\hdl{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd{##2}\hddu{##2}\hdl{##2}\cf{##2}\vdd{##2}
+% \or
+%  \vd{##2}\hddl{##2}\hdu{##2}\cf{##2}\vdd{##2}
+% \or
+%  \vdd{##2}\hddl{##2}\hdu{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd{##2}\hddu{##2}\hddl{##2}\cf{##2}\vd{##2}
+% \or
+%  \vdd{##2}\hdu{##2}\hdl{##2}\cf{##2}\vdd{##2}
+% \else
+% \fi
+%\or%7
+% \ifcase ##1
+%  \vdd{##2}\hddu{##2}\hddl{##2}\cf{##2}\vd{##2}
+% \or
+%  \vdd{##2}\hddu{##2}\hdl{##2}\cf{##2}\vdd{##2}
+% \or
+%  \vd{##2}\hddl{##2}\hddu{##2}\cf{##2}\vdd{##2}
+% \or
+%  \vdd{##2}\hdu{##2}\hddl{##2}\cf{##2}\vdd{##2}
+% \else
+% \fi
+%\or%8
+% \vdd{##2}\hddu{##2}\hddl{##2}\cf{##2}\vdd{##2}
+%\else
+%  \PackageError{chemexec}{Wrong argument in lw}
+%\fi
+%}}
+
+%\DeclareRobustCommand\lwbar[3][0]{
+%\ensuremath{
+%\ifcase ##3
+%\or%1
+% \ifcase ##1
+%  \vd{##2}\cf{##2}
+% \or
+%  \hdu{##2}\cf{##2}
+% \or
+%  \cf{##2}\vd{##2}
+% \or
+%  \hdl{##2}\cf{##2}
+% \else
+% \fi
+%\or%2
+% \ifcase ##1
+%  \vd{##2}\hdu{##2}\cf{##2}
+% \or
+%  \hdu{##2}\cf{##2}\vd{##2}
+% \or
+%  \hdl{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd{##2}\hdl{##2}\cf{##2}
+% \or
+%  \vd{##2}\cf{##2}\vd{##2}
+% \or
+%  \hdu{##2}\hdl{##2}\cf{##2}
+% \else
+% \fi
+%\or%3
+% \ifcase ##1
+%  \vd{##2}\hdu{##2}\cf{##2}\vd{##2}
+% \or
+%  \hdu{##2}\hdl{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd{##2}\hdl{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd{##2}\hdu{##2}\hdl{##2}\cf{##2}
+% \else
+% \fi
+%\or%4
+% \vd{##2}\hdu{##2}\hdl{##2}\cf{##2}\vd{##2}
+%\or%5
+% \ifcase ##1
+%  \vd{##2}\hdu[\@elpairh]{##2}\hdl{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd{##2}\hdu{##2}\hdl{##2}\cf{##2}\vd[\@elpairv]{##2}
+% \or
+%  \vd{##2}\hdl[\@elpairh]{##2}\hdu{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd[\@elpairv]{##2}\hdu{##2}\hdl{##2}\cf{##2}\vd{##2}
+% \else
+% \fi
+%\or%6
+% \ifcase ##1
+%  \vd[\@elpairv]{##2}\hdu[\@elpairh]{##2}\hdl{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd{##2}\hdu[\@elpairh]{##2}\hdl{##2}\cf{##2}\vd[\@elpairv]{##2}
+% \or
+%  \vd{##2}\hdl[\@elpairh]{##2}\hdu{##2}\cf{##2}\vd[\@elpairv]{##2}
+% \or
+%  \vd[\@elpairv]{##2}\hdl[\@elpairh]{##2}\hdu{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd{##2}\hdu[\@elpairh]{##2}\hdl[\@elpairh]{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd[\@elpairv]{##2}\hdu{##2}\hdl{##2}\cf{##2}\vd[\@elpairv]{##2}
+% \else
+% \fi
+%\or%7
+% \ifcase ##1
+%  \vd[\@elpairv]{##2}\hdu[\@elpairh]{##2}\hdl[\@elpairh]{##2}\cf{##2}\vd{##2}
+% \or
+%  \vd[\@elpairv]{##2}\hdu[\@elpairh]{##2}\hdl{##2}\cf{##2}\vd[\@elpairv]{##2}
+% \or
+%  \vd{##2}\hdl[\@elpairh]{##2}\hdu[\@elpairh]{##2}\cf{##2}\vd[\@elpairv]{##2}
+% \or
+%  \vd[\@elpairv]{##2}\hdu{##2}\hdl[\@elpairh]{##2}\cf{##2}\vd[\@elpairv]{##2}
+% \else
+% \fi
+%\or%8
+% \vd[\@elpairv]{##2}\hdu[\@elpairh]{##2}\hdl[\@elpairh]{##2}\cf{##2}\vd[\@elpairv]{##2}
+%\else
+%  \PackageError{chemexec}{Wrong argument in lwbar}
+%\fi
+%}}
+
+%\DeclareRobustCommand\elecpair[3][0]{
+%\ensuremath{
+%\ifcase ##3
+%\or%1
+% \ifcase ##1
+%  \vd[\@elpairv]{##2}\cf{##2}
+% \or
+%  \cf{##2}\vd[\@elpairv]{##2}
+% \else\fi
+%\or%2
+%  \hdl[\@elpairh]{##2}\hdu[\@elpairh]{##2}\cf{##2}
+%\or%3
+% \ifcase ##1
+%  \vd[\@elpairv]{##2}\hdl[\@elpairh]{##2}\hdu[\@elpairh]{##2}\cf{##2}
+% \or
+%  \hdl[\@elpairh]{##2}\hdu[\@elpairh]{##2}\cf{##2}\vd[\@elpairv]{##2}
+% \else\fi
+%\else
+%\fi
+%}}
+
+
+
+}{
+\providecommand\ox[2]{ \ensuremath{\accentset{\text{#1}}{\text{#2}}} }
+\providecommand\Hpl{\ensuremath{\text{H}\op}}            % Protonen
+\providecommand\Hyd{\ensuremath{\text{OH}\om}}           % Hydroxid
+
+%\providecommand\lw[3][0]{
+%\ensuremath{
+%\ifcase #3
+%\or%1
+% \ifcase #1
+%  \vd{#2}\text{#2}
+% \or
+%  \hdu{#2}\text{#2}
+% \or
+%  \text{#2}\vd{#2}
+% \or
+%  \hdl{#2}\text{#2}
+% \else
+% \fi
+%\or%2
+% \ifcase #1
+%  \vd{#2}\hdu{#2}\text{#2}
+% \or
+%  \hdu{#2}\text{#2}\vd{#2}
+% \or
+%  \hdl{#2}\text{#2}\vd{#2}
+% \or
+%  \vd{#2}\hdl{#2}\text{#2}
+% \or
+%  \vd{#2}\text{#2}\vd{#2}
+% \or
+%  \hdu{#2}\hdl{#2}\text{#2}
+% \else
+% \fi
+%\or%3
+% \ifcase #1
+%  \vd{#2}\hdu{#2}\text{#2}\vd{#2}
+% \or
+%  \hdu{#2}\hdl{#2}\text{#2}\vd{#2}
+% \or
+%  \vd{#2}\hdl{#2}\text{#2}\vd{#2}
+% \or
+%  \vd{#2}\hdu{#2}\hdl{#2}\text{#2}
+% \else
+% \fi
+%\or%4
+% \vd{#2}\hdu{#2}\hdl{#2}\text{#2}\vd{#2}
+%\or%5
+% \ifcase #1
+%  \vd{#2}\hddu{#2}\hdl{#2}\text{#2}\vd{#2}
+% \or
+%  \vd{#2}\hdu{#2}\hdl{#2}\text{#2}\vdd{#2}
+% \or
+%  \vd{#2}\hddl{#2}\hdu{#2}\text{#2}\vd{#2}
+% \or
+%  \vdd{#2}\hdu{#2}\hdl{#2}\text{#2}\vd{#2}
+% \else
+% \fi
+%\or%6
+% \ifcase #1
+%  \vdd{#2}\hddu{#2}\hdl{#2}\text{#2}\vd{#2}
+% \or
+%  \vd{#2}\hddu{#2}\hdl{#2}\text{#2}\vdd{#2}
+% \or
+%  \vd{#2}\hddl{#2}\hdu{#2}\text{#2}\vdd{#2}
+% \or
+%  \vdd{#2}\hddl{#2}\hdu{#2}\text{#2}\vd{#2}
+% \or
+%  \vd{#2}\hddu{#2}\hddl{#2}\text{#2}\vd{#2}
+% \or
+%  \vdd{#2}\hdu{#2}\hdl{#2}\text{#2}\vdd{#2}
+% \else
+% \fi
+%\or%7
+% \ifcase #1
+%  \vdd{#2}\hddu{#2}\hddl{#2}\text{#2}\vd{#2}
+% \or
+%  \vdd{#2}\hddu{#2}\hdl{#2}\text{#2}\vdd{#2}
+% \or
+%  \vd{#2}\hddl{#2}\hddu{#2}\text{#2}\vdd{#2}
+% \or
+%  \vdd{#2}\hdu{#2}\hddl{#2}\text{#2}\vdd{#2}
+% \else
+% \fi
+%\or%8
+% \vdd{#2}\hddu{#2}\hddl{#2}\text{#2}\vdd{#2}
+%\else
+%  \PackageError{chemexec}{Wrong argument in lw}
+%\fi
+%}}
+
+%\providecommand\lwbar[3][0]{
+%\ensuremath{
+%\or%1
+% \ifcase #1
+%  \vd{#2}\text{#2}
+% \or
+%  \hdu{#2}\text{#2}
+%  \text{#2}\vd{#2}
+% \or
+%  \hdl{#2}\text{#2}
+% \else
+% \fi
+%\or%2
+% \ifcase #1
+%  \vd{#2}\hdu{#2}\text{#2}
+% \or
+%  \hdu{#2}\text{#2}\vd{#2}
+% \or
+%  \hdl{#2}\text{#2}\vd{#2}
+% \or
+%  \vd{#2}\hdl{#2}\text{#2}
+% \or
+%  \vd{#2}\text{#2}\vd{#2}
+% \or
+%  \hdu{#2}\hdl{#2}\text{#2}
+% \else
+% \fi
+%\or%3
+% \ifcase #1
+%  \vd{#2}\hdu{#2}\text{#2}\vd{#2}
+% \or
+%  \hdu{#2}\hdl{#2}\text{#2}\vd{#2}
+% \or
+%  \vd{#2}\hdl{#2}\text{#2}\vd{#2}
+% \or
+%  \vd{#2}\hdu{#2}\hdl{#2}\text{#2}
+% \else
+% \fi
+%\or%4
+% \vd{#2}\hdu{#2}\hdl{#2}\text{#2}\vd{#2}
+%\or%5
+% \ifcase #1
+%  \vd{#2}\hdu[\@elpairh]{#2}\hdl{#2}\text{#2}\vd{#2}
+% \or
+%  \vd{#2}\hdu{#2}\hdl{#2}\text{#2}\vd[\@elpairv]{#2}
+% \or
+%  \vd{#2}\hdl[\@elpairh]{#2}\hdu{#2}\text{#2}\vd{#2}
+% \or
+%  \vd[\@elpairv]{#2}\hdu{#2}\hdl{#2}\text{#2}\vd{#2}
+% \else
+% \fi
+%\or%6
+% \ifcase #1
+%  \vd[\@elpairv]{#2}\hdu[\@elpairh]{#2}\hdl{#2}\text{#2}\vd{#2}
+% \or
+%  \vd{#2}\hdu[\@elpairh]{#2}\hdl{#2}\text{#2}\vd[\@elpairv]{#2}
+% \or
+%  \vd{#2}\hdl[\@elpairh]{#2}\hdu{#2}\text{#2}\vd[\@elpairv]{#2}
+% \or
+%  \vd[\@elpairv]{#2}\hdl[\@elpairh]{#2}\hdu{#2}\text{#2}\vd{#2}
+% \or
+%  \vd{#2}\hdu[\@elpairh]{#2}\hdl[\@elpairh]{#2}\text{#2}\vd{#2}
+% \or
+%  \vd[\@elpairv]{#2}\hdu{#2}\hdl{#2}\text{#2}\vd[\@elpairv]{#2}
+% \else
+% \fi
+%\or%7
+% \ifcase #1
+%  \vd[\@elpairv]{#2}\hdu[\@elpairh]{#2}\hdl[\@elpairh]{#2}\text{#2}\vd{#2}
+% \or
+%  \vd[\@elpairv]{#2}\hdu[\@elpairh]{#2}\hdl{#2}\text{#2}\vd[\@elpairv]{#2}
+% \or
+%  \vd{#2}\hdl[\@elpairh]{#2}\hdu[\@elpairh]{#2}\text{#2}\vd[\@elpairv]{#2}
+%  \vd[\@elpairv]{#2}\hdu{#2}\hdl[\@elpairh]{#2}\text{#2}\vd[\@elpairv]{#2}
+% \else
+% \fi
+%\or%8
+% \vd[\@elpairv]{#2}\hdu[\@elpairh]{#2}\hdl[\@elpairh]{#2}\text{#2}\vd[\@elpairv]{#2}
+%\else
+%  \PackageError{chemexec}{Wrong argument in lwbar}
+%\fi
+%}}
+}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - Anionen --------------------------------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\IfFileExists{mhchem.sty}{
+  \providecommand\nitrat{\ensuremath{\cf{NO3}}}
+  \providecommand\nitrit{\ensuremath{\cf{NO2}}}
+  \providecommand\sulfat{\ensuremath{\cf{SO4}}}
+  \providecommand\sulfit{\ensuremath{\cf{SO3}}}
+  \providecommand\phosphat{\ensuremath{\cf{PO4}}}
+  \providecommand\phosphit{\ensuremath{\cf{PO3}}}
+  \providecommand\carbonat{\ensuremath{\cf{CO3}}}
+}{
+  \providecommand\nitrat{\ensuremath{\text{NO}_3}}
+  \providecommand\nitrit{\ensuremath{\text{NO}_2}}
+  \providecommand\sulfat{\ensuremath{\text{SO}_4}}
+  \providecommand\sulfit{\ensuremath{\text{SO}_3}}
+  \providecommand\phosphat{\ensuremath{\text{PO}_4}}
+  \providecommand\phosphit{\ensuremath{\text{PO}_3}}
+  \providecommand\carbonat{\ensuremath{\text{CO}_3}}
+}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - Exkurs-Umgebung definieren -------------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\define@key{exkurs}{toc}[\@exkurs@toc]{%
+    \renewcommand{\@exkurs@currenttoc}{#1}}%
+\define@key{exkurs}{color}[\@exkurs@color]{%
+    \renewcommand{\@exkurs@currentcolor}{#1}}%
+\presetkeys%
+  {exkurs}
+  {toc=\@exkurs@toc,color=\@exkurs@color}
+  {}
+\def\@kopfrule{%
+\tikz{\shade[top color=\@exkurs@currentcolor] (0,0) rectangle ($(\textwidth,-3mm)$);}
+}
+\def\@fussrule{%
+\tikz{\shade[top color=white,bottom color=\@exkurs@currentcolor] (0,0) rectangle ($(\textwidth,-3mm)$);}
+}
+
+\newenvironment{exkurs}[2][]%
+{\setkeys{exkurs}{#1}%
+\vspace{1.2\baselineskip}\par\noindent\@kopfrule\par\noindent\vspace{.8\baselineskip}%
+ \parbox[c]{\textwidth}{\centering\bfseries\Large{\color{\@exkurs@currentcolor}\@exkurs@name:~}#2}%
+ {\addcontentsline{toc}{\@exkurs@currenttoc}{{\textcolor{\@exkurs@currentcolor}{\@exkurs@name}:~}#2}}\\%
+}%
+{%
+\vspace{.8\baselineskip}\par\noindent\@fussrule\vspace{1.2\baselineskip}%
+  \normalsize\par%
+}%
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - Beispiel-Umgebung ----------------------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\newcommand{\@bsprule@currentlinecolor}{}%
+\define@key{bsprule}{linecolor}[\@bsprule@linecolor]{%
+    \renewcommand{\@bsprule@currentlinecolor}{#1}}%
+\presetkeys%
+  {bsprule}
+  {linecolor=\@bsprule@currentlinecolor}
+  {}
+
+% Zähler für die Beispiele
+\if@usechapter
+  \newcounter{beispiel}[chapter]
+  \renewcommand\thebeispiel{\thechapter.\arabic{beispiel}:}
+\else
+  \newcounter{beispiel}
+  \renewcommand\thebeispiel{\arabic{beispiel}:}
+\fi
+% Umgebung
+\newenvironment{beispiel}[1][linecolor=\@bsprule@linecolor]%
+ {\setkeys{bsprule}{#1}%
+  \refstepcounter{beispiel}%
+  \vspace{1.5\baselineskip}{\color{\@bsprule@currentlinecolor}\hrule}\par\nobreak%
+  \vspace{3pt}\noindent\small\textbf{\@beispiel@name~\thebeispiel}%
+  \par\nobreak\@afterheading%
+ }%
+ {\par\nobreak\vspace{2pt}{\color{\@bsprule@currentlinecolor}\hrule}\vspace{1.5\baselineskip}\normalsize\ignorespacesafterend\par%
+ }%
+
+% zweites, drittes, ... Beispiel
+\providecommand\bsp{\refstepcounter{beispiel}\par\noindent\textbf{\@beispiel@name~\thebeispiel}\newline}%
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - Definitions-Umgebung -------------------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\define@key{definition}{shadecolor}[\@definition@shadecolor]{%
+    \renewcommand{\@definition@currentshadecolor}{#1}}%
+\define@key{definition}{color}[\@definition@color]{%
+    \renewcommand{\@definition@currentcolor}{#1}}%
+\define@boolkey{definition}{shade}[true]{%
+  \ifKV@definition@shade
+    \@shadedtrue
+  \else
+    \@shadedfalse
+  \fi
+}
+
+\presetkeys%
+  {definition}
+  {shadecolor=\@definition@shadecolor,color=\@definition@color}
+  {}
+
+\newenvironment{definition}[1][]
+ { \setkeys{definition}{#1}%
+   \if@shaded
+     \def\FrameCommand{\fboxsep=\FrameSep \colorbox{\@definition@currentshadecolor}}%
+   \fi
+   \MakeFramed{\advance\hsize-\width \FrameRestore}%
+   \noindent{\large\scshape\color{\@definition@currentcolor}\unterstr{Definition}~}%
+ }
+ { \endMakeFramed%
+ }
+
+\newenvironment{defformel}[1][\hsize]{%
+  \def\FrameCommand{\colorbox{white}}%
+  \MakeFramed {\hsize#1\advance\hsize-\width\FrameRestore}\centering}%
+ {\endMakeFramed}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - Aufgaben, sectionweise gezählt ---------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\if@useaufg
+  \gdef\@aufgabe@actualgroesse{\csname\@aufgabe@groesse\endcsname}
+  %\RequirePackage{etex}
+  %\reserveinserts{32000}
+  \IfFileExists{ifthen.sty}{%
+    \RequirePackage{ifthen}
+    \IfFileExists{calc.sty}{%
+      \RequirePackage{calc}
+      \if@usechapter
+        \newcounter{@aufgabe}[chapter]
+        \renewcommand{\the@aufgabe}{\thechapter.\arabic{@aufgabe}}
+      \else
+        \newcounter{@aufgabe}[section]
+        \renewcommand{\the@aufgabe}{\arabic{@aufgabe}.}
+      \fi
+      \newcounter{@Aufgabe}
+      \if@usechapter
+        \newcounter{@zaehler}[chapter]
+      \else
+        \newcounter{@zaehler}
+      \fi
+      \newcounter{@nummer}
+      %%% der eigentliche Befehl
+      \DeclareRobustCommand\aufgabe[1]{%
+        \refstepcounter{@aufgabe}%
+        \stepcounter{@Aufgabe}%
+        \stepcounter{@zaehler}%
+        \stepcounter{@nummer}%
+        \bigskip%
+        \par\noindent{\@aufgabe@actualgroesse\bfseries{\color{\@numbers@numcolor}\the@aufgabe}~%
+        \ifthenelse{\equal{####1}{}}%
+        {\@aufgabe@name}{####1}}%
+        \par\nobreak\@afterheading\normalfont\medskip%\newline%
+      }%
+    }{%
+      \PackageError{chemexec}{%
+      The `calc' package is apparently unavailable.\MessageBreak
+      Turn off the `aufgabe' option and come back again.}{%
+      If you want to use the possibilties of the `aufgabe' option,\MessageBreak
+      you have to install the `calc' package from CTAN or wherever\MessageBreak
+      you get your LaTeX  packages.}%
+    }%
+  }{%
+      \PackageError{chemexec}{%
+      The `ifthen' package is apparently unavailable.\MessageBreak
+      Turn off the `aufgabe' option and come back again.}{%
+      If you want to use the possibilties of the `aufgabe' option,\MessageBreak
+      you have to install the `ifthen' package from CTAN or wherever\MessageBreak
+      you get your LaTeX  packages.}%
+  }
+
+\makeatletter
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - Lösungen eingeben ----------------------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\newcounter{@loesung}
+\newcounter{@Loesung}
+%\newcommand{\@loesung@text}{}
+\edef\empty#1{#1}
+\DeclareRobustCommand\loesung[2][\@loesung@titel]{
+  %\renewcommand{\@loesung@text}{#2}
+  \setcounter{@loesung}{\value{@zaehler}}
+  \stepcounter{@Loesung}
+  {%
+  \csname protected@xdef\expandafter\endcsname\csname @tempa\endcsname{%
+  \expandafter\gdef\csname @loesung@nr\arabic{@Loesung}\endcsname{\the@loesung}}%
+  \expandafter\expandafter\expandafter
+  }\csname @tempa\endcsname
+  {%
+  \csname protected@xdef\expandafter\endcsname\csname @tempa\endcsname{%
+  \if@usechapter
+    \expandafter\gdef\csname @loesung@kap\arabic{@Loesung}\endcsname{\thechapter}
+  \else
+    \expandafter\gdef\csname @loesung@kap\arabic{@Loesung}\endcsname{\arabic{section}}
+  \fi}%
+  \expandafter\expandafter\expandafter
+  }\csname @tempa\endcsname
+  \expandafter\gdef\csname @loesung@loes\arabic{@Loesung}\endcsname{ #2}
+  %\savebox{\csname loes\arabic{Loesung}\endcsname}{#2}
+  \expandafter\gdef\csname @loesung@name\arabic{@Loesung}\endcsname{\noexpand #1}
+}
+
+\newcounter{@mylist}
+\renewcommand\the@mylist{\alph{@mylist})}
+\newcommand*{\alphlabel}[1][\stepcounter{@mylist}\the@mylist]{\normalfont #1\hfil}
+\newenvironment{alphlist}{
+\begin{list}{}%
+            {\let\makelabel\alphlabel
+             \setlength\labelwidth{15pt}%
+             \setlength\leftmargin{\labelwidth+\labelsep+.5em}%
+            }%
+}{
+\setcounter{@mylist}{0}
+\end{list}
+}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - Alle Lösungen ausgeben ------------------------------------------------------------ %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\newcounter{@zahl}
+\newcounter{@a}
+\def\@loesung@altKap{0}
+\DeclareRobustCommand\makeloesung{%
+ \@ifundefined{@ausgabe}{\@ifundefined{dolo}{%
+  \setcounter{@zahl}{\value{@Loesung}+1}%
+  \setcounter{@a}{1}%
+  \whiledo { \value{@a} < \value{@zahl} }{%
+       \def\@loesung@ausg{\csname @loesung@loes\arabic{@a}\endcsname}%
+       \edef\@loesung@Name{\csname @loesung@name\arabic{@a}\endcsname}%
+       \edef\@loesung@Kap{\csname @loesung@kap\arabic{@a}\endcsname}%
+       \edef\@loesung@Nr{\csname @loesung@nr\arabic{@a}\endcsname}%
+       \@ifundefined{@loesung@loes\arabic{@a}}%
+       {}%
+       {\ifnum \@loesung@Kap=\@loesung@altKap%
+          \bigskip%
+          \par\nobreak\@afterheading\noindent%
+        \else%
+          \if@usechapter%
+            {\smallskip%
+            \par\noindent\hspace*{.1\textwidth}\color{\@numbers@numcolor}{\LARGE\@loesung@Kap. \chaptername{}}}\\%
+            \par\nobreak\@afterheading\vspace{2pt}{\color{\@numbers@numcolor}\hrule\vspace{4pt}\noindent}%
+          \else%
+            \bigskip%
+            \par\noindent%
+          \fi%
+        \fi%
+        %\medskip%
+        {\@aufgabe@actualgroesse\bfseries{\color{\@numbers@numcolor}\if@usechapter\@loesung@Kap.\fi\@loesung@Nr\if@usechapter\else.\fi~}\@loesung@Name}\medskip\newline%
+        \@loesung@ausg%
+       }%
+       \let\@loesung@altKap=\@loesung@Kap%
+       \stepcounter{@a}%
+  }%
+  \bigskip\par%
+  \def\@loesung@ausgabe{voll}%
+ }{\errmessage{Sie haben schon doloesung verwendet!}}}{\errmessage{Sie haben makeloesung schon vorher verwendet!}}%
+}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% - Lösungen section-weise ausgeben --------------------------------------------------- %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\DeclareRobustCommand\doloesung{%
+ \@ifundefined{ausgabe}{%
+  \setcounter{@a}{\value{@nummer}-\value{@zaehler}+1}%
+  \setcounter{@zahl}{\value{@nummer}+1}%
+  \whiledo { \value{@a} < \value{@zahl} }{%
+       \edef\@loesung@Name{\csname @loesung@name\arabic{@a}\endcsname}%
+       \edef\@loesung@Kap{\csname @loesung@kap\arabic{@a}\endcsname}%
+       \edef\@loesung@Nr{\csname @loesung@nr\arabic{@a}\endcsname}%
+       \def\@loesung@ausg{\csname @loesung@loes\arabic{@a}\endcsname}%
+       \@ifundefined{@loesung@loes\arabic{@a}}%
+       {}%
+       {\bigskip
+        \par\noindent%%
+        {\@aufgabe@actualgroesse\bfseries{\color{\@numbers@numcolor}\if@usechapter\@loesung@Kap.\fi\@loesung@Nr\if@usechapter\else.\fi~}\@loesung@Name}\par\nobreak\@afterheading\medskip%\newline%
+        \@loesung@ausg%
+       }%
+       \let\@loesung@altKap=\@loesung@Kap%
+       \stepcounter{@a}%
+  }%
+  \bigskip\par%
+  \setcounter{@zaehler}{0}%
+  \setcounter{@nummer}{\value{@Loesung}}%
+  \def\dolo{voll}%
+ }{\errmessage{Sie haben schon makeloesung verwendet!}}%
+}
+
+\makeatother
+\else
+\fi
\ No newline at end of file
diff --git a/Master/tlpkg/bin/tlpkg-ctan-check b/Master/tlpkg/bin/tlpkg-ctan-check
index c517f6507b6..21674cbdf8a 100755
--- a/Master/tlpkg/bin/tlpkg-ctan-check
+++ b/Master/tlpkg/bin/tlpkg-ctan-check
@@ -75,7 +75,8 @@ my @TLP_working = qw(
     cd cd-cover cdpbundl
     cell cellspace censor cfr-lm
     changebar changelayout changepage changes chappg chapterfolder
-    chbibref chem-journal chemarrow chembst chemcompounds chemcono chemfig
+    chbibref chem-journal
+    chemarrow chembst chemcompounds chemcono chemexec chemfig
     chemstyle cherokee
     chess chess-problem-diagrams chessboard chessfss chextras
     chicago chicago-annote chletter chngcntr chronology
diff --git a/Master/tlpkg/tlpsrc/chemexec.tlpsrc b/Master/tlpkg/tlpsrc/chemexec.tlpsrc
new file mode 100644
index 00000000000..e69de29bb2d
--- /dev/null
+++ b/Master/tlpkg/tlpsrc/chemexec.tlpsrc
diff --git a/Master/tlpkg/tlpsrc/collection-science.tlpsrc b/Master/tlpkg/tlpsrc/collection-science.tlpsrc
index d6406f6ee06..fc2aef5ace7 100644
--- a/Master/tlpkg/tlpsrc/collection-science.tlpsrc
+++ b/Master/tlpkg/tlpsrc/collection-science.tlpsrc
@@ -13,6 +13,7 @@ depend bytefield
 depend chemarrow
 depend chemcompounds
 depend chemcono
+depend chemexec
 depend chemstyle
 depend clrscode
 depend complexity