Inspired by a question on chemistry.se (now closed, because it was a cross post from Phys.SE), I observe the mhchem extension can be used here provided the question/answer contains once $\require{mhchem}$* to render e.g., \ce{C6H12O6} (sum formula of e.g. glucose) as $\ce{C6H12O6}$.

In the current second version, the post includes, e.g.,

$$\epsilon_n = 1.775\times10^{-20}\,\text{J}$$

the OP currently defines by $$\epsilon_n = 1.775\times10^{-20}\,\text{J}$$. With mhchem's \pu{} command (physical units) on Chemistry requires $$\epsilon \pu{1.775E-20 J}$$ only. Here on Physics, the resulting $$\epsilon \pu{1.775E-20 J}$$ suggests some support is missing. At present, the nested application $\ce{\pu{3 kg}}$ does not work fully either ($\ce{\pu{3 kg}}$).


  • is this an issue the moderators of Physics may address to the maintainers of Stack¬†Exchange?

  • alternatively, is the use of a different (perhaps more siunitx like) approach more suitable here on Physics?

* As recommended both by the author and comments on Meta Physics here. It is engaged.

  • $\begingroup$ I've been answering questions on this site for 10 years and I don't think I've ever once anything other than vanilla Mathjax. I only see 43 instances of mhchem in the post out of a total of >220k questions & ??? answers. I guess it seems to me that none of this is needed? $\endgroup$
    – Kyle Kanos
    Commented Sep 2, 2023 at 17:53
  • $\begingroup$ @KyleKanos Speculation: perhaps the use of symbols in italics, and (upright) units (with proper, non-breaking space) is less frequent in a typical question on physics, than for (more homework like) questions about physical chemistry on Chemistry (where dimension analysis is/should be used) because questions here on Physics address problems more on a conceptual perspective. $\endgroup$
    – Buttonwood
    Commented Sep 4, 2023 at 16:38
  • 1
    $\begingroup$ My point was that less than 0.008% of all posts (226k questions, 330k posts) on this site have ever used mhchem, so I'm not sure that this qualifies as a problem that needs fixing or even cursory looks. $\endgroup$
    – Kyle Kanos
    Commented Sep 7, 2023 at 16:02
  • $\begingroup$ @KyleKanos With this background, I'm fine to accept mhchem is not a tool this significant on Physics as it is on Chemistry. Case closed. $\endgroup$
    – Buttonwood
    Commented Sep 7, 2023 at 20:15
  • $\begingroup$ @Buttonwood It looks like we don't have the mchem extension isn't enabled by default on Physics. Enabling it might resolve it. But typically, we like to see a more formal request to turn that on for a site. It looks like there was a conversation before, but we might need a fresh ask on that to ensure people can weigh in. $\endgroup$
    – SpencerG StaffMod
    Commented Oct 2, 2023 at 20:31
  • $\begingroup$ Doesn't look like there is any movement on this anywhere, so I am removing the tag and leaving it declined. Feel free to add the tag back on a new request if there is sufficient community support. $\endgroup$
    – SpencerG StaffMod
    Commented Oct 30, 2023 at 19:21
  • 1
    $\begingroup$ @SpencerG It is an application the audience here (physics) does not perceive as much as an advantage as the audience on chemistry. When filing the question, I was not aware how big (or perhaps better: how small) this niche here on physics is. Now that I know better, it is a when in Rome, do as the Romans do which, without regret, is fine. $\endgroup$
    – Buttonwood
    Commented Oct 31, 2023 at 11:31


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