%% 
%%  Ein Beispiel der DANTE-Edition
%%  
%%  2. Auflage
%% 
%%  Beispiel 15-05-5 auf Seite 816.
%% 
%%  Copyright (C) 2016 Herbert Voss
%% 
%%  It 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.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{352.81416pt}
\parindent=0pt
%StartShownPreambleCommands
\usepackage{chemformula,mhchem}
%StopShownPreambleCommands
\begin{document}
Paket \texttt{chemformula}: \ch{H2O ->[ + H+ ] H3O+}  \par
Paket \texttt{mhchem}: \ce{H2O ->[+\ce{H+}] H3O+}
\end{document}