248 PIGMENTS 



o 



/ \ 



CH CH 



I! II 



CH CH 



\ / 

 CO 



Pyrone 



which dissolves in hydrochloric acid, forming an additive com- 

 pound of the formula 



H Cl 



v 



o 



/ \ 



CH CH 



L CH 



\ / 

 CO 



the oxygen becoming tetravalent. Such additive compounds 

 of anthoxanthins with acids are easily dissociated and do not 

 occur in plants, though it will be seen on page 250 that in the 

 case of the anthocyanins analogous compounds do actually 

 occur naturally. 



REFERENCES. 



Kostanecki : " Bull. soc. chim. Paris," 1903, [3], 29, i-xxxvii. 



Perkin, A. G., and others: " J. Chem. Soc. Lond.," 1895,67; 1896, 69; 

 1897, 71 ; 1898, 73 ; 1899, 75, etc. 



Wheldale : " Proc. Camb. Phil. Soc.," 1909, 15, 137; " Biochem. J.," 1914, 

 8, 204, etc. 



ANTHOCYANIN, PHYCOERYTHRIN, AND 

 PHYCOPHAEIN. 



Occurring in the cell sap, often in sufficient quantity to 

 mask entirely the green colour of the chlorophyll, are a 

 number of pigments, other than chlorophylls, belonging to 

 various classes of chemical compounds. 



Under the collective heading of Anthocyanin are included 

 a number of such pigments of a blue, red, or violet tint occur- 

 ring in the flowers, fruits, or leaves of many plants.* The 

 first representative of the class to be isolated in a state of 

 purity by Willstatter and Everest f was Cyanin, the blue 



* An historical account of our knowledge of these pigments is given by 

 Everest in " Science Progress," 1915, 9, 597. 



t Willstatter and Everest: " Annalen," 1913, 401, 189. 



