THE CHEMISTRY OF COFFEE 173 



CO CO 



/\ CH3 /\ CHs 



/ \ / / \ / 



CHs N C N +2H CH3 N C N 



i II >c« -^ I 11 >CH + Ha 



CO C N CO C N 



/ 



N N 



I I 



CHs CH3 



Chlorcaffeine Caffeine 



(or 1:3:7 trimethyl-8-chlordIoxy- (or 1:3:7 dimethyl-2:6 dioxy- 

 purine) purine) 



The constitutional formulae of the other principal members of the 

 purine group are given below: 



Adenine or Hypoxanthine or Guanine or 



6 aminopurine 6 oxypurine 2 amino 6 oxypurine 



N==CNH2 NH— CO NH— CO 



I I II 



II II 

 CH C NH CH C NH NH2C C NH 



II II >« II II >" II II >™ 



N C N N C N N C N 



The composition of coffee has been studied by a large number of 

 investigators, but much remains to be accomplished. Subsequent 

 statements refer to the seeds of Cojfea arahlca L, unless otherwise 

 qualified. The chief alkaloid in coffee is caffeine, and varies in 

 amount from 0.5% to 2.2% with an average content of about 

 1.3%. Gorter has shown that it occurs in coffee as potassium caffeine 

 chlorogenate. Paladino isolated crystals of the base coffearine from 

 coffee-extract by boiling with milk of lime. Coffearine, C14H16O4N2, 

 occurs as colorless deliquescent needles, melting at I40°C. and giving 

 a faint alkaline reaction. It forms a hydrochloride, C14H16O4N2 

 HCI.H2O, melting at i8o°C. Graf repeated and confirmed Pala- 

 dlno's experiment. Nitrogenous constituents of coffee other than 

 caffeine are In need of research. The proteins, however, have been 

 studied by some investigators, and have been found to consist of 



