How to enable mhchem extension?

I'm trying to follow the examples documented at https://docs.moodle.org/27/en/Chemistry_notation_using_mhchem#via_MathJax for enabling the mhchem extension. I've created a custom configuration at admin/config/content/mathjax which looks like this:

{
  TeX: {
    extensions: ["mhchem.js","color.js","AMSmath.js","AMSsymbols.js","noErrors.js","noUndefined.js"]
  },
  "tex2jax":{
    "inlineMath":[
      ["$","$"],
      ["\\(","\\)"],
      ["\[\ce{","}\]"],
      ["$$\ce{","}$$"],
      ["\(\ce{","}\)"]
    ],
    "processEscapes":"true"
  },
  "showProcessingMessages":"true",
  "messageStyle":"none"
}

This isn't working, so two questions:

- Does this module support extensions?
- Any advice for getting mhchem working properly?