ANALYSIS AND ADULTERATIONS OF COFFEE. 83 



the volatile products generated in the operation. By roasting 

 coffee in an apparatus which allows of the recovery of all the 

 volatile products, it has been ascertained that if it be car- 

 ried away with the volatile products, it can only be in such 

 small quantity as to be inappreciable by weight, and cannot ex- 

 plain the considerable loss which takes place during roasting, 

 carefully performed. The loss is experimentally found to 

 equal nearly one-half of the caffeine originally existing in the 

 coffee. M. "Wurtz has demonstrated that the lost caffeine has 

 been transformed into a volatile base methylamine, or methyl- 

 ammonia (C 4 H 6 N). The following are the facts which prove 

 the change of caffeine into methylamine during coffee-roasting. 

 " If pure caffeine be submitted to the action of heat, and the 

 vapor be carried through a tube heated to about 300 Centi- 

 grade (about the heat which is necessary for roasting), and filled 

 with fragments of pumice-stone, which delay the passage of 

 the vaporized matters, only a feeble decomposition occurs ; the 

 greater part remains unchanged, and the little that is decom- 

 posed gives no characteristic product except cyanogen. This 

 experiment tends to prove that it is not the caffeine which 

 furnishes the volatile alkaloid existing in roasted coffee. But a 

 very different result is obtained if, instead of acting on free 

 caffeine, we 'experiment on caffeine in analogous circumstances 

 to those in which it exists in green coffee. It is easy to extract 

 the alkaloid from roasted coffee by distilling the extract of cof- 

 fee, made with cold water, with a weak base, such as lime. 

 The addition of this alkali to an infusion of coffee immediately 

 liberates the methylamine, the special ammoniacal odor of 

 which is readily perceptible." 



In tea the proportion of volatile oil amounts to about one 

 pound in a hundred of the dried leaf, but in roasted coffee it 

 rarely amounts to more than one in fifty thousand ! And yet 

 on the different proportions of this oil which they severally 



