CHEMICAL CONSTITUENTS. 251 



in boiling water, it will yield only some 25 per cent, of 

 soluble matter, while roasted coffee, on the other hand, 

 when completely exhausted by means of boiling water, 

 yields as high as 40 per cent, in some instances. A 

 chemical analysis of the bean after being roasted also 

 shows that it contains 20 per cent, of water and about 60 

 per cent, of cellulose a substance resembling starch or 

 grape sugar. But the agents that especially distinguish 

 coffee from all other substances are the Caffeine, Caffeone 

 and Caffeic, each of which constituents possess virtues 

 and effects peculiar to itself, and produce, by acting in 

 combination, the general effect of coffee. 



Caffeine Is the principle to which coffee owes its 

 refreshing and agreeable properties. It is an inodorous 

 agent, having a slightly bitter taste, and belonging to 

 that group of chemical agents known as alkaloids. It 

 is identical with the theine of tea, and also forms the 

 characteristic principle of cocoa, mate, the guarana and 

 many other plants used by the inhabitants of widely- 

 separated countries, on account of their yielding a slightly 

 exciting and refreshing beverage and apparently forming 

 a necessary diet for mankind in general. Its quantity 

 varies from 0.8 to I per cent, in the different kinds of 

 coffee, being greatest in Martinique and smallest in San 

 Domingo. According to Chandler, pure Caffeine appears 

 in white silky needles, having no odor, and containing 

 about 8 per cent, of water of crystalization, which it parts 

 with at 1 50 C., being apparently soluble in cold water, but 

 much more so in hot, still less so in alcohol and still less 

 in ether, acting as a weak base and dissolving in acids 

 from which it may be crystalized by evaporation. When 

 boiled with fixed caustic alkalies it decomposes and 

 yields methlamine, while heating with basic-hydrates 



