Text containing math above and below equilibrium sign won't compile (using mhchem)

Question

Why won't this compile? I suspect the math inside the []s are preventing compilation. If so how do I make this work? Thanks.

\documentclass[12pt]{article}
\usepackage[version=3]{mhchem}
\begin{document}
\ce{E + S <=> [$k_1$][$k_{-1}$] ES <=>[$k_2$] E + P}
\end{document}

Error:

! Missing $ inserted. $ l.34 ...k_1$}][\ce{$k_{-1}$}] ES <=>[$k_2$] E + P} ?

set it without using math mode: \ce{E + S <=> [k_1][k_{-1}] ES <=>[k_2] E + P}
Very good, I also discovered the space between <=> and [k_1][... is not allowed. :| Thanks!
@Herbert: since you answered first, post your comment as an answer, and I'll delete mine.
It also works with \ensuremath{k_1}, if you wish to have math mode for the common italic math font.

Herbert · Answer 1 · 2011-06-23 18:33:04Z

up vote 2 down vote

set it without using math mode:

\ce{E + S <=> [k_1][k_{-1}] ES <=>[k_2] E + P}

answered Jun 23 '11 at 18:33

Herbert
115k6135339

cgnieder · Answer 2 · 2012-01-13 10:45:49Z

The arguments of mhchem's arrows already are in math mode. So wrapping them in $...$ must go wrong.

\ce{A ->[\Delta] B} % default: math mode

If you would want or need text mode you'd have to use \text{} or mhchem's shortcut:

\ce{A ->T[text mode] B} = \ce{A ->[\text{text mode}] B}

Also there is a second shortcut for "chemistry mode", i.e. using the \ce macro:

\ce{A ->C[H2O] B} = \ce{A ->[\ce{H2O}] B}

2 Answers