ppchtex – Typeset chemical formula diagrams
ppchTeX is a separate module of the ConTeXt macro package for TeX. It seems to be in its final state (having not changed for more than 10 years).
Maybe you are interested in the following packages as well.
- bpchem: Typeset chemical names, formulae, etc
- chemcono: Support for compound numbers in chemistry documents
- lewis: Draw Lewis structures
- elements: Provides properties of chemical elements