mhchem is a bundle for typesetting chemical formulae and Risk and Safety Phrases.
The mhchem bundle consists of two packages: mhchem and rsphrase. The mhchem package provides two commands: one for typesetting chemical molecular formulae and one for typesetting chemical equations with these formulae. The rsphrase package contains the text of all official Risk and Safety (R and S) Phrases that are used to label chemicals. At the time being, these phrases are available in Danish, English, French, German (current spelling), and Spanish.