Input like "${t_2}^\circ\ce C$}" renders failed

[wkh1234]

use https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js

render:

I want render：

[dpvc]

Thanks for the report. It turns out that this is due to an issue with autoloading tex extensions. When the mhchem extension is loaded to process the \ce, the space between \ce and C is lost, and the macro becomes \ceC, which is not defined. That is the source of the issue, here.

One solution would be to use \ce{C} rather than \ce C, and another would be to force mhchem to be loaded initially rather than autoloaded via

MathJax = {
  loader: {load: ['tex/mhchem']},
  tex: {packages: {'[+]': ['mhchem']}}
};

[dpvc]

I have made a pull request to resolve the issue.