6io 



SCIENCE PROGRESS 



H CI 



y\ /<X OH 



HO A/ V-QoH acid H ° 



C— OH 0H reduct 



ion 



OH 



c — O 0H 



OH 



C— OH 



O 



H 



C 



II 



o 



° A 



H 



O H 



H 

 Flavonol derivative. II. Colourless, or faintly coloured intermediate product. 



- H.,0 HO 



S\S 



CI 

 i 



o 



+ H 2 



C— OH 



OH 



OH 

 OH 



in. 



%/%r/ 



o y 



H H 



III. Anthocyan pigment. 



The most recent paper upon this subject is an account ot 

 the most valuable and beautiful work yet published upon the 

 anthocyan pigments. It is a brief account of the continuation of 

 the investigations of Willstatter and his collaborators (Willstatter, 

 Mieg, Bolton, Zollinger, Mallison, and Nolan, Sitzber. der k. 

 Akad. Wiss. Berlin, 1914, 12, 402). They have examined the pig- 

 ments of the rose (gallica), cranberry, grape (deep coloured wine 

 grape), bilberry, delphinium (purple), pelargonium (scarlet), 

 and hollyhock (deep red), and in each case isolated the pure 

 crystalline glucoside, as chloride, and from it, by hydrolysis, 

 obtained the pure crystalline non-glucoside. They have estab- 

 lished beyond doubt the formulae and structure of these 

 compounds — indeed, this paper represents so far-reaching and 

 important an advance in the chemistry of the anthocyan pigments, 

 that its value cannot be over-estimated. 



The methods of isolation of the glucosides have been so 

 improved, that they now consist of but a few simple operations ; 

 thus, for example, in the case of the grape pigment, it is only 

 necessary to extract with cold glacial acetic acid, and after 

 nitration, precipitate the pigment by means of ether, dissolve 

 the washed precipitate in excess oi warm aqueous picric acid 





