Sometimes when I have to review edits I'm not sure if is right to chose always the latex formatting instead of plain text.

For example is necessary to convert NaCl to $NaCl$ or 1.3g to $1.3 g$ I think sometimes we risk to increase the time for visualize the page, in my old computer I notice the difference between a formatted page and normal text.

Another performance question, is $\ce{H2O}$ more slower to load then $H_{2}O$? In general when we should prefer $\ce{}$?

  • $\begingroup$ Related: Do we really need to badger everyone to use MathJax for chemical formulas? $\endgroup$
    – user7951
    Aug 11, 2016 at 20:03
  • 2
    $\begingroup$ Your example conversions make things worse. First "NaCl" is correct (upright font). Your conversion (italic font) is wrong. "1.3g" is wrong as there is a spacing missing before the "g". Your convertions does not fix it and even adds a second error (italic font). This has nothing to do with LaTeX/MathJax or not. One correct way would be $\ce{NaCl}$ and $\pu{1.3g}$. $\endgroup$
    – mhchem
    Aug 12, 2016 at 12:09
  • $\begingroup$ @mhchem that were examples that I found in the suggested edits... I am actually saying the opposite that NaCl is correct and that we should not focus on these little details. $\endgroup$
    – G M
    Aug 12, 2016 at 13:37

3 Answers 3


I use $\ce{}$ a lot in my own posts and in edits - except in titles.

I find mhchem much more intuitive for chemistry and I'm glad I can use it here. Reactions conditions noted on arrows do add information.

Moreover, I find $\LaTeX$ notation in general very helpful when discussing units; a lot of students are having problems with these and frequently get stuck in their calculations.

Are there similar discussions on meta of the helpful sciences (aka mathematics and physics) on SE? They should have the same performance problems then.

So far, I did not worry about rendering performance. Should I?


Edits should make posts better. Better means getting rid of errors, so both of the examples you gave should be flat-out rejected because they introduce errors.

Chemicals should be formatted upright. Thus, using NaCl is okay. If there are no chemicals that require subscripted or superscripted digits/symbols, then it is fine to use normal typeface throughout the entire post (and an edit replacing only these to use mhchem is to be rejected for not improving the post significantly). Using $NaCl$ is wrong and bad. Using $\ce{NaCl}$ is good, and should be the preferred variant if there is at least one instance of $\ce{H2O}$ or similar.

Replacing $H_2O$ ($H_2O$) or H2O (H2O) with $\ce{H2O}$ ($\ce{H2O}$) is a good thing and should always be done.

Similarly for numbers with units. The correct way to typeset them is with a non-breaking space between value and unit. Thus, 3.14g is wrong, as is $3.14g$ (actually worse: it introduces wrong italics!) as is $3.14~g$. The best way to typeset this is $3.14~\mathrm{g}$ and that should be used whenever possible. The newer version of mhchem even allows us to write $\pu{3.14g}$ as a shortcut (see here for details).

Edits that turn a wrong formatting into a correct one and thus improve the overall condition of the post should always be accepted (unless other errors are introduced). Edits that turn an OK formatting into a correct one need to be judged individually.


After some years I have been around here, I think that these kind of minor changes like CaO to $\ce{CaO}$ should be avoided. Because they distract reviewers from much important changes and edits.

I think the right praxis would be to change also these formatting issuses if there are also other more important changes to be done in the post.

  • 1
    $\begingroup$ I wholeheartedly agree, there is no need to mathjax/mhchem every single thing (including plain numbers) if it is unnecessary (no superscripts/subscripts etc.) That said I suppose there's nothing wrong with it if it's someone with >2k rep whose edits don't need to be reviewed, unless the page is mathjax heavy and takes a long time to load. $\endgroup$ Aug 23, 2016 at 4:53
  • $\begingroup$ @orthocresol I recently noticed, that in some cases, due to the font we are currently using, it looks very odd not to use MathJax for plain numbers. For example when you write 78.5%, which you later use in an equation $M_{\mathrm{av}}(\text{air}) \approx 21.5\% M(\ce{O2}) + 78.5\% M(\ce{N2})$. $\endgroup$ Oct 3, 2017 at 9:59
  • $\begingroup$ @Martin-マーチン, I just consider it visually unattractive to use $2$ in the middle of a sentence. I think $78.5\%$ is fine, and especially in the context you gave, (when things look the same, the human eye recognises them more easily). At the end of the day I guess it's personal preference. $\endgroup$ Oct 3, 2017 at 11:38

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