# chemformula, height of plus sign

How do I get the plus sign to be aligned with the arrow i.e. change the height of the plus sign?

\documentclass{scrreprt}

\usepackage[english]{babel}
\usepackage{chemformula}

\begin{document}

\ch[plus-space=8pt]{CH2=CH2 + 3 O2 -> 2 CO2 + 2 H2O}

\end{document}


• Are you open to using the mhchem package instead? – erik Dec 4 '14 at 2:25
• I'm liking the shape of the arrows in the chemformula package better. If there is a way to change the shape of the arrows used in the mhchem package to the shapes used in chemformula, I'd be open to use the mhchem package. – Shery Dec 4 '14 at 2:41

With a recent version (at least v4.9) of chemformula you can say:

\ch[plus-output-symbol = \raisebox{.2ex}{+}]{CH2=CH2 + 3 O2 -> 2 CO2 + 2 H2O}


You can also do the opposite (this works also with older versions):

\ch[arrow-yshift = -.2ex]{CH2=CH2 + 3 O2 -> 2 CO2 + 2 H2O}


The .2ex in my examples is just an initial guess…

\documentclass{scrartcl}
\usepackage{chemformula}
\setchemformula{ plus-space = .8em }

\begin{document}

\ch[plus-output-symbol = \raisebox{.2ex}{+}]{CH2=CH2 + 3 O2 -> 2 CO2 + 2 H2O}

\ch[arrow-yshift = -.2ex]{CH2=CH2 + 3 O2 -> 2 CO2 + 2 H2O}

\end{document}


Here is a solution using mhchem and the arrows=pgf-filled option (to get similar arrows). Note the option requires manual loading of the tikz package.

\documentclass{extarticle}
\usepackage{tikz}
\usepackage[version=3]{mhchem}
\mhchemoptions{arrows=pgf-filled}
\begin{document}
\ce{CH2=CH2 + 3 O2 -> 2 CO2 + 2 H2O}
\end{document}