Oleum Picis Liquidae (U. S. P.)—Oil of Tar.
Related entry: Pix Liquida (U. S. P.)—Tar
"A volatile oil distilled from tar"—(U.S. P.).
Preparation.—When common wood-tar is distilled, that portion of less density than water passing over, is called oil of tar; a residue known as pitch is left in the retort.
Description and Chemical Composition.—"An almost colorless liquid when freshly distilled, but soon acquiring a dark reddish-brown color, and having a strong, tarry odor and taste. Specific gravity, about 0.970 at 15° C. (59° F.). It is readily soluble in alcohol, the solution being acid to litmus paper"—(U. S. P.).
The density of oil of tar is apt to vary according to the amounts of its various constituents present. If prepared from coniferous tars turpentine is likely to form a large portion of the oil. Oil of tar contains empyreumatic substances, several acids, among them acetic acid, and a number of hydrocarbons.
Action and Medical Uses.—This oil has the uses of Tar (which see). It is applied locally in scaly and other forms of skin diseases. It has been used for the relief of chronic coughs. The dose is 1 to 5 drops in emulsion or capsule.