CAFFEINE 37B 



cese), or from the dried seeds of Coffea arabica Linne (nat. 

 ord. rubiaceae), and found also in other plants. 



Habitat. — Indigenous to Africa, and cultivated in other 

 tropical countries. 



Derivation. — Crushed coffee is treated with successive 

 portions of boiling water, and the resulting solution is 

 precipitated with lead acetate and filtered. Hydrogen sul- 

 phide decomposes the excess of lead acetate remaining in 

 the filtrate. The latter is then concentrated by evaporation 

 and neutralized with ammonia water. Caffeine crystallizes 

 on cooling. The alkaloid is purified by charcoal and recrys- 

 tallization. 



Properties. — Fleecy masses of long, flexible, white crys- 

 tals, possessing a silky lustre, without odor, having a bitter 

 taste, and permanent in the air. Soluble in '80 parts of 

 water, 33 parts of alcohol, 555 parts of -ether, or 7 parts of 

 chloroform. Also soluble in about 2 parts of boiling water, 

 and very soluble in boiling alcohol. Caffeiue is neutral to 

 litmus paper. Caffeine exists, curiously enough, as the 

 active principle of the national non-alcoholic beverages in 

 use all over the world. Coffee contains .6-2.2 per cent, of 

 caffeine, together with glucose, fat, vegetable casein, tannic 

 acid, and an empyreumatic oil developed by roasting, i. e., 

 caffeone. Tea contains 1.36-3. per cent, of caffeine, or theine, 

 and also a volatile oil and tannic acid. Guarana (the seeds 

 of Paullinia cupana) contains 4 to 5 per cent, of caffeine; 

 mate, or Paraguay tea (the leaves of Ilex paraguayensis), 

 contains .45-1.2 per cent. Caffeine is found in kola nut (the 

 fruit of Sterculia acuminata), used as a beverage in Africa, 

 and now as a nervous stimulant in human medicine, and is 

 allied to theobromine, occuring in chocolate beans, and to 

 cocaitfe, existing in coca leaves. 



Incompatibility. — Caffeine is incompatible with mercury 

 salts, potassium iodide and tannic acid. 



Z^ose.— H., gr.vii.-xv. (.5-1.); D., gr.ss.-iii. (.03-.2), accord- 

 ing to size. 



