THE ALKALOID OF COCOA. 937 



the fat skimmed off, and the residue pressed out. The beans are now roasted, 

 husked, and very finely ground. The mass is heated to 70-80 C., packed in sacks 

 of ticking, and submitted to pressure between previously warmed or steam-heated 

 plates. The fat expressed, about 30-35 per cent, is filtered through dry filters. The 

 pure residue, containing 10-15 per cent of oil, is made into chocolate. For the prep- 

 aration of an entirely fat-free cocoa powder, the roasted and ground beans are ex- 

 hausted with benzine or ether. 



Theobromine, the alkaloid of cocoa, is very closely related chemically 

 (it is dimethyl xanthine, C 5 H2(CH 3 )2lSr4O2, while caffeine is trimethyl 

 xanthine, CsH^CHs^l^C^) to caffeine, the alkaloid of tea and coffee, 

 and has similar effects on the system; the power possessed by the bev- 

 erages prepared from these substances, " to cheer and not to inebriate," 

 being largely due to the presence of these alkaloids. 



Separated from the bean, it is a white powder, permanent in the air, 

 crystallizable in microscopic rhombic needles, and having a very bitter 

 taste. While neutral in reaction, it acts as a weak base, uniting with 

 acids to form crystallizable salts, which become basic on treatment with 

 water; its salts of volatile acids give up their acids on heating, at or 

 below 100 C. According to Blyth, 1 it begins to sublime at 134 C., 

 and yields distinct crystals at 170 0. and above; Keller, 1854 2 , reports 

 the subliming point as 290"-295 C. ; other writers note it as about 290 

 C. Treuuiann 3 has reported its solubility in water to be 1 in 148.5 at 

 100 C., and 1 in 1,600 at 17 C.; in absolute alcohol, 1 in 422.5 at the 

 boiling point, and 1 in 4,284 at 17 C.; in boiling chloroform, 1 in 105. 

 Husemann 4 states its solubility in water to be 1 in 55 at 100 C., 1 in 

 G60 at 20 C., and 1 in 1,600 at C.; in cold alcohol, 1 in 1,460, and in 

 boiling alcohol, 1 in 47; in .cold ether, 1 in 17,000, and in boiling ether, 

 1 in 600 ; more soluble in chloroform and warm amyl alcohol than in 

 water, less soluble in benzol, and insoluble in petroleum ether. 



1 Op. cit., note 3, p. 936 of this work. 



2 Op. Git., note 3, p. 938 of this work. 



3 Archiv. d. Pharm., [3] 13, 5; Jahresb. d. Chern., 1878, 872. 



4 Husemann's Pflanzenstoife. 



