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Undefined control sequence \pu

As far as I can tell, this is something that is supposed to render correctly. I didn't open the page in the browser, but it is being used in both the question and the answers.

Question link for reference

  • 1
    The question is here: Melting point of aspirin, contradicting sources. It’s working on the web and the mobile site. This has been reported on Meta.Chemistry.SE: Undefined control sequence \pu in official SE Android app and is status-bydesign. From MathJax in the Android App: “Unfortunately the app uses a different version than the website. That does include the recent updates to mhchem, especially the \pu{...} command.”. – user289905 Mar 23 '19 at 23:31
  • IIRC correctly the app uses an webview to render the post. I would expect it takes the same MathJax lib as it uses on main so I wouldn't expect this difference in behavior. Other posts render correctly? – rene Mar 23 '19 at 23:33
  • @rene My main site is Mathematics, so I see lots of mathjax and it works fine. – Matt Samuel Mar 23 '19 at 23:34
  • I'm amazed people still use the app. It's like using some very old, unsupported, browser. Maybe not IE6, but it's getting there quickly. – Shadow Keeps Social Distance Mar 24 '19 at 9:03
  • @Shadow The delay in navigation on the mobile site is frustrating. – Matt Samuel Mar 24 '19 at 11:15
  • @Matt and the responsive design of the full site mode? It's not perfect and not yet done but already pretty good IMO, and proper replacement of the not-so-good mobile theme which should go away. – Shadow Keeps Social Distance Mar 24 '19 at 11:18
  • @Shadow you mean using the full site on mobile? – Matt Samuel Mar 24 '19 at 12:25
  • @Matt exactly. That's the goal of responsive design, to make the site useable and readable on all screens, without the need for whole different set of CSS/JS like it's used today. :) – Shadow Keeps Social Distance Mar 24 '19 at 12:26
  • @shadow When I use the desktop site there's a bunch of text that is too small to read, and I need to zoom in. – Matt Samuel Mar 24 '19 at 17:45

The issue is the \pu{...} MathJax command used in the question. This problem has been reported a few times on Chemistry.SE's meta. One such report got tagged , and another one got this answer from @Martin - マーチン ♦:

Unfortunately the app uses a different version than the website. That does include the recent updates to mhchem, especially the \pu{...} command.

While \dfrac can and should be avoided in general, that is not really true for the mhchem updates, as we would lose all the recent development discussed on meta.

We'll have to see and wait how the developers will continue their work on the app.

Since app development has ceased, the app will likely not get fixed. In the meantime, using the web version of Stack Exchange on my Android displays the MathJax properly, though it is inconvenient.

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  • Yes the app gives a much more rapid response and I'm not afraid of accidentally hitting something with the side of my hand to navigate away. – Matt Samuel Mar 24 '19 at 0:22

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