# mhchem extension This extension adds to KaTeX the `\ce` and `\pu` functions from the [mhchem](https://mhchem.github.io/MathJax-mhchem/) package. ### Usage This extension isn't part of core KaTeX, so the script should be separately included. Write the following line into the HTML page's ``. Place it *after* the line that calls `katex.js`, and if you make use of the [auto-render](https://katex.org/docs/autorender.html) extension, place it *before* the line that calls `auto-render.js`. ```html ``` If you remove the `defer` attribute from this tag, then you must also remove the `defer` attribute from the `