Origin. - The hydrate of the diatomic alcohol terpin, prepared by mixing rectified oil of turpentine, alcohol, and nitric acid, allowing the mixture to stand for three or four days in shallow porcelain dishes, collecting the crystals which have formed, drying on absorbent paper, and recrystallizing in a cold solution of alcohol.

Description and Properties. - Colorless, lustrous, rhombic prisms, nearly odorless, and having a slightly aromatic and somewhat bitter taste. Permanent in the air. Soluble in about 250 parts of water and in 10 parts of alcohol. Terpin hydrate should be kept in well-stoppered bottles.

Dose. -2-30 grains (0.12-2.0 Gm.) [2 grains (0.125 Gm.), U. S. P.].

Physiological Action. - Terpin hydrate is a powerful antiseptic, its action resembling that of turpentine, though inferior in strength.

Therapeutics. - Externally and Locally. - The drug is used in the form of lozenges and as an inhalant in chronic tracheitis and chronic bronchitis.

Internally. - Terpin hydrate may be used for the same purposes as terebene, being considered by some physicians superior to the latter drug in bronchial affections.

Administration. - Terpin hydrate may be given in lozenges, emulsion, or aromatic elixir, although the most judicious method of administration, perhaps, is in capsules.