An alkaloid (B.P.), or proximate principle of feeble alkaloidal power (U.S.P.), generally prepared from the dried leaves of Camellia Thea, or from the dried seeds of Coffea arabica (Nat. Ord., Rubiaceae); or from the Guarana, and occurring also in other plants.

Characters. - Colourless, silky, inodorous, acicular crystals.

Preparation. - By evaporating aqueous infusions from which astringent and colouring matters have been removed.

Solubility. - Soluble in 80 parts of cold water, the solution having a faintly bitter taste and being neutral to litmus. More soluble in boiling water and in rectified spirit, and very soluble in chloroform; sparingly soluble in ether.

Reactions. - Above 212° F. they melt and volatilise without decomposition. Treated with a crystal of chlorate of potassium and a few drops of hydrochloric acid, and the mixture evaporated to dryness in a porcelain dish, a reddish residue results, which becomes purple when moistened with ammonia. In an aqueous solution of the alkaloid, tannic acid gives a white precipitate, soluble in excess of the reagent.

Dose. - 1 to 5 grains.