152 



Dr. A. E. Everest and Mr. A. j. Hall. 



the blue pigment of the cornflower was the potassium or calcium salt of cyanin. 

 Willstatter and Mieg proved that the violet flowers of wild larkspur contained 

 the neutral colour base of delphinin,* whilst Willstatter and Boltonf showed 

 that in the scarlet pelargonium the pigment pelargonin was accompanied by 

 a considerable amount of tartaric acid, and that it could form stable salts 

 (oxonium) with such weak acids as acetic acid. The further work of 

 Willstatter and his collaborators has resulted in the isolation of the colour 

 bases of the pigments : pelargonin, cyanidin and delphinin, and also of the 

 colourless pseudo-bases of pelargonidin, cyanidin and delphinidin. 



In support of their theory of complex salts, and their explanation of the 

 colours in flowers based thereon, Shibata, Shibata and Kasiwagi describe the 

 preparation of various blue and blue-green compounds and give analyses of 

 them. 



Exhaustive and careful examination of the data given by them has brought 

 the present authors to the conclusion that much of the evidence they set out 

 is of an unsatisfactory character, and that their conclusions concerning their 

 experimental results are misleading. 



The present authors are convinced that very valuable results may often be 

 obtained by the careful examination of plant extracts or impure pigments, 

 but only if and when due allowance is made for the fact that impurities are 

 present and for the nature of the impurities. In dealing with plant 

 pigments, such allowances can only be made when tlie investigator concerned 

 has himself made a careful study of the pure pigments and has considerable 

 first-hand knowledge of these bodies. It is often the case that access to 

 even the smallest amount of a pure pigment will save endless incorrect 

 deduction from experimental results. It appears to the present authors that 

 sufficient weight has not been attached to this by Shibata, Shibata and 

 Kasiwagi. 



Not only is this the case, but in places their arguments are inconsistent 

 with statements made in other parts of their paper. 



Willstatter, and also Everest, have found, as the result of quantitative 

 work, that under conditions such as Shibata, Shibata and Kasiwagi described 

 for the isolation of their green and blue pigments, the flavonol used is never 

 quantitatively converted into the corresponding anthocyan. Furthermore, it 

 is well known that the addition of metallic acetates in alcoholic solution to 

 flavonol derivatives such as myricetin gives rise to the formation of metal 

 phenolic salts of the flavonols. Hence, when they precipitated their green 

 pigments, it follows that they obtained, not as they imagined, an anthocyan 



* ' Ann.,' vol. 408, p. 67 (1915). 

 . t 'Ann.,' vol. 408, p. 5H (1915). 



