Red cinchona, 10; bitter orange peel, 8; serpentaria, 2; glycerin, 10; alcohol and water (in the proportion of 8 of the former to 1 of the latter), q.s. to make 100.

Properties and Composition of the Cinchona Barks. - The cinchona barks contain varying quantities of the following alkaloids : - Cinchonine (C29H22N2O), cinchonidine (C19H22N2O), quinine (C20H24N2O2), quinidine (C20H24N2O2), quinamine (C19H24 N2O2), conquinamine (C19H24N2O2).

Both the total quantity of alkaloids and the relative proportions of each vary considerably in the barks of the different species of cinchona.

By heating solutions of the cinchona alkaloids with excess of a mineral acid they may be converted into amorphous isomeric alkaloids. Quinine yields quinicine, and cinchonine is converted into cinchonicine.

In addition to the alkaloids, the cinchona barks contain certain acid principles. These are : - (1) Quinic or chinic acid, soluble in water and alcohol, but sparingly so in ether. On oxidation it yields quinone or chinone. (2) Cincho-tannic acid. (3) Quinovic acid.

Cinchona bark also contains quinovin, which by means of hydrochloric acid is resolved into quinovic acid and an uncry-stallisable sugar. It also contains cinchona-red, which is a colouring matter abundantly found in the red bark.

Distinguishing Tests for Cinchona Alkaloids.

U.S.P. Quinina. Quinine. C20H24N2O2.3H2O (crystallised);

378. - An alkaloid prepared from different species of cinchona.

Preparation. - By adding to the solution of the sulphate a quantity of water of ammonia or solution of soda, just sufficient to precipitate the alkaloid.

Although it is not separately mentioned in the B.P., it is used in the preparation of citrate of iron and quinine.