Bell1 reports 2.20 per cent of cocoa red in raw beans; Muter, 3.96 per cent.

Gum. - It is precipitated from the aqueous solution of the fat-free beans by alcohol. After drying it resembles gum arabic; by treatment with nitric acid, yields mucic acid; and, when ignited, leaves an ash consisting of basic phosphate of magnesium. Its specific rotatory power is [a] j = + 68.6 (Boussingault2).

The beans contain 2.17 per cent of gum according to an analysis by Bell,1 and 2.5 per cent according to Boussingault.2

Tartaric acid. - Weigmann3 estimates tartaric acid by precipitation of the aqueous extract, after neutralization with ammonia, with calcium chloride, redissolving in hydrochloric acid and reprecipitating with sodium hydrate. The amount of tartaric acid is calculated from the amount of calcium oxide contained in this precipitate. By this method he found 4.34 per cent to 5.82 per cent of tartaric acid in the raw, whole beans. Boussingault2 reports 3.4 per cent and 3.7 per cent.

The aroma of cocoa is considered to be due to the presence of minute quantities of an aromatic volatile oil. Boussingault2 proves its presence by distillation of the roasted grains with water.