I'm trying to typeset a chemical equation using the mhchem package, and I want to bold just one part of the equation (to emphasize the product, in this case).

If I type \ce{a A + b B -> c \textbf{C} + d D}, then that produces a A + b B → c C + d D. That's perfectly fine, of course. But I cannot put any more complex chemical formulas within the \textbf{} command. If I enter, for example, \ce{NH3(g) + HCl(g) -> \textbf{NH4Cl}(s)}, ammonium chloride is typeset as NH4Cl(s), without the subscript.

I tried writing the subscript manually (NH_4Cl), but $\ce{NH3(g) + HCl(g) -> \textbf{NH_4Cl}(s)}$ did not work, and instead gave me a bunch of errors (missing $, extra } or forgotten $, missing {, and missing }).

I'm pretty new here so I'm not exactly sure how this MWE thing works — I don't have much that works, but as far as I can tell the code I was using to try things out seems to be pretty close to a MWE. Please let me know if I should provide anything else.




\ce{a A + b B -> c C + d D}

\ce{a A + b B -> c \textbf{C} + d D}

\ce{NH3(g) + HCl(g) -> \textbf{NH4Cl}(s)}


An \textbf is a hard break inside a \ce. What goes inside \textbf's argument is not processed by the mhchem package.

This is the way to go.

\ce{NH3(g) + HCl(g) -> $\textbf{\ce{NH4Cl}}$(s)}

Use $ to indicate that you want to escape mhchem parsing (mhchem does the correct guessing that \textbf and the next {} belong together, but using $ is much clearer). Then use \textbf, then use \ce inside.

The $ part (or the \textbf for that matter) might interrupt the mhchem flow. The succeeding (s) works fine, here, but you might not be always so lucky (for instance, a $\textbf{4}$ would not be recognized as a number).

  • 1
    Approved! I should have used the same solution as you. – Sebastiano Jul 14 '19 at 9:23


  • using \ce in math mode (this dose change the output when you use a text font that looks different from the math font, or in headings, as commented by @mhchem) and
  • using \mathbf instead of \textbf

See this example:


$\ce{NH3(g) + HCl(g) -> \mathbf{NH_4Cl}(s)}$
\ce{NH3(g) + HCl(g) -> NH_4Cl(s)}

enter image description here

  • 2
    Using \ce in math mode does change the output when you use a text font that looks different from the math font, or in headings. – mhchem Jul 14 '19 at 6:21
  • @mhchem thanks. I have updated the answer. – muzimuzhi Z Jul 14 '19 at 18:00

It works flawlessly with chemformula, with the difference that the indeterminate coefficients should be typeset in math.




\ch{$a$ A + $b$ B -> $c$ C + $d$ D}

\ch{$a$ A + $b$ B -> $c$ \textbf{C} + $d$ D}

\ch{NH3(g) + HCl(g) -> \textbf{NH4Cl}(s)}


enter image description here

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