Polychrest

Pol"y*chrest (?), n. [Gr. ? useful for many purposes; poly`s many + ? useful, fr. ? to use: cf. F. polychreste.] (Med.) A medicine that serves for many uses, or that cures many diseases. [Obs.]

Polychrest salt (Old Med. Chem.), potassium sulphate, specifically obtained by fusing niter with sulphur.