904 



FOODS AND FOOD ADULTERANTS. 



TJ>e anii f cnff< 



* The descriptions of samples are based on the dealer's statements. 



t Numbers given are parts in 100 of mineral matter after deduction of carbon dioxide. Oxygen 

 equivalent to chlorine is not deducted. 

 { Soluble in solution of sodium carbonate. 



One of the most important constituents of coffee is the alkaloid caf- 

 feine. This alkaloid is identical, chemically and physiologically, with 

 that present in tea and termed "theine." Coffee contains a much 

 smaller proportion of this alkaloid than is found in tea leaves. Caf- 

 feine was discovered in 1820 by Bunge, 1 and was isolated some time 

 afterwards by Pelletier, 2 Robiquet, 3 Caventon, and Garrot. This alka- 

 loid is also found in the leaves of the coffee tree. According to Payen 4 

 caffeine is present as a caffetaunate. Caffeine may readily be obtained 

 from coffee by extraction with chloroform. The alkaloid separated in 

 this way, after purification, is obtained on evaporating the solvent in 

 beautiful white silky, librous crystals. Unroasted coffees contain from 

 a little less than 1 per cent to approximately 2 per cent of caffeine. 

 Payen 5 reports from 3.5 to 5 per cent caffeine plus caffetannate of 

 potassium, the free alkaloid amounting to .8 per cent. Caffeine" melts 

 at 224 to 228 C., sublimes at 187 C., is soluble in 58 parts of wafer 

 at 20 C., in 9.5 parts of water at 100 C., in 21 parts alcohol, in 545 

 parts of ether and in 9 parts of chloroform at 20 C. According to 

 Lapean 7 the solubility of caffeine in alcohol at 15.5 C. is 1 part in 150 

 of the solvent. "Blyth cautions the analyst against drying this alka 



1 Schweigg. Jour. Cheni. Phys. 31, 3()8. 



8 Jour. Pharin. [2], 12, 229. 



: <0/,. ,-it., 234. 



Ann. diim. phys. [3] 16, 108; Jahrosl). ii. <1. Fortsoh. d. Clicni. 1SI!>. IX<1. 



*Ann. cliiin. phys. [3] 26, 108; Juluvsl.. ii. d. FortsHi. d. ('linn. ISI'l. ISii. 



Vierteljahreschr. ]>r. I'lumu 16, 167. 



M'luiriii. .1. Trans. |3], 11, 902; Jalnvsl.. d.Clinn. 1SS1, 902. 



"Foods: Their coinjHwition and analysis. A. W. Hlyth. 



