THE ANTHOCYAN PIGMENTS 611 



solution, and allow to cool, when fine crystals of the picrate 

 separate. The picrate may be decomposed by methyl-alcoholic 

 hydrochloric acid, and the chloride thus obtained recrystallised 

 from aqueous alcoholic hydrochloric acid. This method is also 

 applicable to the bilberry, cranberry, and hollyhock pigments. 

 In other cases, the isolation of the glucosides was obtained by 

 use only of the knowledge of the solubilities of their chlorides. 



Both the results of analyses and those of decomposition of 

 the pigments by heating with alkali, agree in pointing to a 

 formula that is closely related to that of flavonol. 



All these pigments, on heating with alkali, yielded phloro- 

 glucinol and a phenolic derivative of benzoic acid (which varied 

 with the pigment taken). In each case all but one of the 

 hydroxyl groups present in the molecule can be accounted for in 

 the decomposition products, hence the remaining one, as in 

 flavonol, must be attached to a carbon atom in the pyrone ring. 

 The evidence produced proves that all the anthocyan pigments 

 examined were derived from IV or V, but there is at present 

 insufficient evidence for decision between these two formulae. 



CI CI 



I I 



2 



C-OH 3 



%/%r/ VV/ 



O V iv. O 



H H 



CH 



-OH 



As on heating with alkali, cyanidin chloride (C^HnCCl) 

 yields phloroglucinol and 3*4 dioxy-benzoic acid ; pelargonidin 

 chloride (C, 5 H n 5 Cl) yields phloroglucinol and p-oxy-benzoic 

 acid ; and delphinidin chloride (C 15 H n 7 Cl) yields phloro- 

 glucinol and gallic acid, it is evident that cyanidin has two 

 hydroxyl groups substituted in the positions marked 1 and 2, 

 pelargonidin one only, in the position 2, whilst delphinidin has 

 three, in the positions 1, 2 and 3. 



From analyses of the colourless iso-forms of the anthocyan 

 pigments, Willstatter has shown that they are produced by the 



