537. COFFEA.—COFFEE. The seeds of Cof'fea arab'ica Linné. Habitat: Southern Arabia and Abyssinia; cultivated in South America, Java, and various tropical countries. The fruit is a roundish berry, about the size of a large cherry, becoming dark purple, and containing two seeds, which are inclosed within a membranous covering, and a purplish pulp. These seeds, when freed from the pericarp, form the coffee of the market. They are brownish-green or bluish-gray, plano-convex, the flat surface being elliptical, with a longitudinal groove curving deeply into the horny albumen; odor peculiar, faint, growing stronger by age; taste sweetish, somewhat astringent. Good berries are hard and sink readily in water. Soft, light, dark-colored berries should be rejected.
CONSTITUENTS.—Its properties depend upon the alkaloid caffeine (2 to 8 per cent.), the constituent common to most of the stimulating beverages. It also contains sugar, tannic acid, caproic acid, fat, etc. When roasted, the sugar is converted into caramel, the caffeic acid partially into methylamine, and several volatile and empyreumatic substances (caffeone) are formed. Pyridine has been separated from these mixed products due to roasting, giving to coffee its peculiar aroma. It loses from 15 to 18 per cent. of moisture in drying.
Preparation of Caffeine (Theine).—Precipitate infusion of tea or coffee with lead acetate; remove lead from filtrate with H2S; concentrate second filtrate, neutralize with NH4OH, and allow it to cool, when caffeine will crystallize out. An aqueous solution of caffeine does not form a precipitate with Mayer's reagent.
ACTION AND USES.—Cerebrospinal stimulant, tonic; aids digestion and allays hunger and fatigue by lessening tissue waste.
537a. COFFEA TOSTA, N.F.—Yielding not less than 1 per cent. of caffeine.