3o6 TANNINS 



Properties. 



Chlorogenic acid is an optically active substance, a^ = 

 — 33-1 ; it is not precipitated by gelatine ; with ferric chloride 

 it gives a green colour. 



Boiled with mineral acids it breaks up into catfeic and 

 quinic acids and similar hydrolysis is effected by Mucor or 

 Penicillium * or by the tannase of Aspergillus.^; 



According to Freudenberg % the substance described in 

 the older literature as caffetannic acid is a mixture of chloro- 

 genic acid with other acids. 



Oparin§ considers chlorogenic acid to be a respiratory 

 chromogen which is oxidized by atmospheric oxygen to a 

 green pigment capable of acting as an hydrogen acceptor. 

 This subject is dealt with more fully in volume ii. 



FURTHER REFERENCE. 

 Fischer : " Untersuchungen iiber Depside," Berlin, 1919. 



* Gorter : " J. Amer. Chem. Soc," 1909, 247, 184. 

 + Freudenberg : " Ber. deut. chem. Gesells.," 1920, 53, 232. 

 + Ibid. : " Die Chemie der natiirlichen Gerbstofie," Berlin, 1920, 

 p. 76. 



§Oparin: " Biochem. Zeit.," 1921, 124, 90; 1927, 182, 155. 



