Derivation.—A mixture of hydrocarbons, chiefly of the marshgas series, obtained by distilling off the lighter and more volatile portions from petroleum and purifying the residue when it has the desired consistence.

Properties.—A colorless, or more or less yellowish, oily transparent liquid without odor or taste; or giving off, when heated, a faint odor of petroleum. Insoluble in water; scarcely soluble in cold or hot alcohol, or cold absolute alcohol; but soluble in ether, chloroform, carbon disulphide, oil of turpentine, benzine, benzol and fixed and volatile oils.

PETROLATUM—VASELINE—COSMOLINE

Derivation.—A mixture of hydrocarbons, chiefly of the marshgas series, obtained by distilling off the lighter and more volatile portions from petroleum and purifying the residue when it has reached the desired melting point.

Properties.—A fat-like mass of about the consistence of an ointment varying in color from yellowish to light amber, having not more than a slight fluorescence, even after being melted; transparent in thin layers, completely amorphous and without odor or taste, or giving off when heated a faint odor of petroleum. In other respects soft petrolatum has the solubility of liquid petrolatum.

PETROLATUM ALBUM—WHITE PETROLATUM

Derivation.—A mixture of hydrocarbons, chiefly of the methane series, obtained by distilling off the lighter and more volatile portions from petroleum and purifying the residue.

Properties.—A white, unctuous mass, of about the consistency of an ointment, transparent in thin layers, completely amorphous; without odor or taste. Otherwise it resembles, in solubility, petrolatum.

Action.—All preparations of petrolatum are valuable emollients. They soothe, protect and soften parts to which they are applied and are superior to animal or vegetable fats or oils in not becoming rancid.

Uses.—Petrolatum may be used alone, or as an excipient in the preparation of ointments, but does not aid the absorption of drugs (as do alcohol, glycerine, chloroform, animal oils and fats), for it is not itself absorbed even when administered internally. Petrolatum exerts a demulcent action upon the mucous membrane of the alimentary tract, and may be prescribed in electuary or capsule in inflammation thereof. Liquid petrolatum is useful given internally in piles (dogs one-half ounce twice daily) to soften the feces. It is also very serviceable with menthol and camphor (equal parts, fifteen grains to one ounce) dropped in the nostrils (with a medicine dropper) for dogs with acute nasal catarrh. Petrolatum is sold universally under the proprietary names of vaseline and cosmoline, and is often combined with antiseptics for medical and surgical purposes in skin diseases and upon inflamed mucous membranes, blisters and abraded surfaces and sores. It is one of the most useful agents in lubricating instruments, protecting metal from rust, and is sometimes employed as a vehicle for electuaries. It should not be used as a base for blisters or other ointments where absorption is desired.