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second— the beetroot-red group — those which gave red lead 

 salts, and whose acid solution showed no change of colour, or 

 slight change to violet-red, on making alkaline. The anthocyan 

 pigments are, however, of so varying a character that this simple 

 classification of Weigert by no means covers all cases, for even 

 by comparison only of the colour changes on acidification or 

 making alkaline, and by means of the lead compounds, quite a 

 number of sub-groups can be observed. 



Overton (Pring. Jahrber. f. wiss. Bot. 1899, 33, 222) also 

 came to the conclusion that a considerable number of different 

 anthocyan pigments existed. 



In all the above-mentioned work, either qualitative results 

 only were aimed at, or the preparations were amorphous and 

 lacking the essential characteristics of chemically pure products. 

 From these observations, however, it had become clear that in 

 the anthocyans a large class of new pigments were awaiting 

 chemical investigation, and, moreover, in the light of the work 

 of Heise and Glan, it was evident that at least certain of these 

 pigments must be looked upon as belonging to a class of nitro- 

 gen-free glucosides. An expression of this view was made by 

 Molisch in 1905. 



In 1903, two papers, both describing the same set of experi- 

 ments, were published by Griffiths {Berichte. 36, 3959 ; and Chern. 

 News, 88, 249), which, had they been followed up, might have 

 had very considerably greater influence on this field of work 

 than they have had. He describes the preparation for the first 

 time of an anthocyan in a crystalline condition. His work was 

 carried out with geranium and verbena flowers, but the pig- 

 ment obtained from the latter contained nitrogen and sulphur 

 and was doubtless impure ; that from the geranium contained 

 neither of these elements, and was the only one analysed. His 

 method of preparation consisted in extracting the pigment from 

 the petals with 90% alcohol, and, after filtration, evaporating in 

 vacuo. The residue thus obtained was extracted with absolute 

 alcohol, filtered, and the filtrate again evaporated in vacuo, when 

 the pigment separated in crystalline form. He did not attempt 

 to decide whether the pigment was a glucoside or no. The 

 description of his experiments was very superficial and imper- 

 fect ; thus, for example, the fact that a fresh 90% alcoholic extract 

 of geranium petals has a fine scarlet colour, but passes in a few 

 minutes to a practically colourless solution, which, however, re- 



