# Arrows chemical equations

I want to write the following equation; note the arrow underneath BaSO_4 and the H_2O over the \longrightarrow.

Is that possible with the chemist package, which I already use for my chemical equations? Any help would be appreciated.

• No problem. Could you add a link to the chemist package? It doesn't seem to be on CTAN... – jub0bs Nov 7 '13 at 20:06

There are two alternatives I'd consider. The first is the well known mhchem package:

\documentclass{article}
\usepackage[version=4]{mhchem}
\begin{document}

\ce{Na2SO4 ->[H2O] Na+ + SO4^2-}

\ce{(2Na+,SO4^2- ) + (Ba^2+, 2Cl- ) -> BaSO4 v + 2NaCl}

\end{document}


The second is the chemformula package from the chemmacros bundle:

\documentclass{article}
\usepackage{chemformula}
\begin{document}

\ch{Na2SO4 ->[ H2O ] Na+ + SO4^2-}

\ch{( 2 Na+ ,SO4^2- ) + (Ba^2+ , 2 Cl- ) -> BaSO4 v + 2 NaCl}

\end{document}


Their syntax is slightly different and both are bit picky about spaces that need to be there in order to parse the input, however in different places... you'll also notice small differences in the output for example with regard to spacing.

But since you've mentioned the chemist package (which is part of the XyMTeX bundle): the reactions are also possible with it:

\documentclass{article}
\usepackage{chemist}
\begin{document}

\begin{chemmath}
Na_{2}SO_{4}
\reactrarrow{0pt}{1.5cm}{\ChemForm{H_2O}}{}
Na^{+} + SO_{4}^{2-}
\end{chemmath}

\begin{chemmath}
(2 Na^{+},SO_{4}^{2-}) + (Ba^{2+},2 Cl^{-})
\reactrarrow{0pt}{1cm}{}{}
BaSO_{4} + 2 NaCl
\end{chemmath}

\end{document}


• isn't there a way to represent the precipitate arrow like the one in my question? – Kira Nov 8 '13 at 20:35
• @HediNaily with TikZ this should be possible. I don't know any chemistry package that provides something like it, though... – clemens Nov 8 '13 at 20:37

Here is a chemfig solution:

\documentclass{article}
\usepackage{chemfig}
\begin{document}
\schemestart
\chemfig{Na_2SO_4}
\arrow{->[\footnotesize\chemfig{H_2O}]}
\chemfig{Na^+}\+\chemfig{SO_2^{-}}
\schemestop

\bigskip

\schemestart
(2\chemfig{Na^+}, \chemfig{SO_4^{2-}})
\+
(\chemfig{Ba^{2+}}, 2\chemfig{Cl^{-}})
\arrow(.mid east--.mid west)
\chemname[1pt]{\chemfig{BaSO_4}}{\chemfig{-[,0.75]-[5,.3,,,-stealth]}}\+2\chemfig{NaCl}
\schemestop
\end{document}