Pet`ro*la"tum (?), n. (Chem. & Pharm.) A semisolid unctuous substance, neutral, and without taste or odor, derived from petroleum by distilling off the lighter portions and purifying the residue. It is a yellowish, fatlike mass, transparent in thin layers, and somewhat fluorescent. It is used as a bland protective dressing, and as a substitute for fatty materials in ointments. U. S. Pharm.

&fist; Petrolatum is the official name for the purified product. Cosmoline and vaseline are commercial names for substances essentially the same, but differing slightly in appearance and consistency or fusibility.