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.
PIX LIQUIDA—TAR
An empyreumatic oleo-resin obtained by the destructive distillation of the wood of various species of pines, especially that of Pinus palustris.
Habitat.—United States.
Properties.—Thick, viscid, semi-fluid, blackish-brown; heavier than water, transparent, in thin layers, becoming granular and opaque with age; odor empyreumatic terebinthinated; taste sharp empyreumatic. Tar is slightly soluble in water; soluble in alcohol, fixed or volatile oils and solutions of potassium or sodium hydrate.
Constituents.—Oil of turpentine; methylic alcohol; creosote; guaiacol; phenol; pyrocatechin; toluol; xylol; acetic acid; acetone; resins.
Dose.—Horses and cattle, 1⁄2 to 1 oz.; sheep and pigs, 1 to 2 dr.; dogs, 1⁄4 to 1 dr. Oil of tar should be diluted with alcohol, glycerine, syrup or mucilage.