M. Wheldale 125 



dust is added, an intense red or purplish-red coloration is produced 

 (Abderhalden, 1). 



Hence the coloration given by many plant extracts in alcoholic 

 solution when treated with hydrochloric acid and sodium amalgam or 

 zinc dust is obviously due to the presence of Havone in the extracts, and 

 it is useless to postulate the nature of the reaction in the absence of 

 analyses of the red product. 



The following points must then be considered: 



(a) The question as to the identity of the artificial and natural 

 anthocyanins. The only characteristic reactions in common between 

 the two substances are the red colour with acids, the green colour with 

 alkalies and the decolorisation with sodium bisulphite, and it is possible 

 that these reactions might be given by two derivatives which were 

 similar, though not necessarily identical. The artificial anthocyanin, 

 after removal of alcohol and hydrochloric acid by evaporation, is soluble 

 in ether and in water, whereas natural anthocyanins are always insoluble 

 in ether and also almost insoluble in water excej)t when in the condition 

 of a glucoside. 



(b) If the natural and artificial anthocyanins are not in any cases 

 identical, the reaction is still interesting as showing that coloured 

 products, very similar in properties to anthocyanin, can be obtained 

 by reduction from the flavones. 



(c) If the natural and artificial anthocyanins are in all cases 

 identical, which is unlikely, then the reactions, by which the latter 

 are formed, must be very different frcjm those taking place in its 

 formation in the plant, since, for instance, ai'tificial anthocj'anin can 

 be produced, according to Combes, from members of the genus Narcissus, 

 which do not form natural anthocyanin. Artificial anthocyanin, on the 

 other hand, cannot be obtained from many species which do produce 

 natural anthocyanin. 



(d) There is a possibility, however, that in some cases natural 

 anthocyanin may be formed by the treatment with nascent hydrogen, 

 as for instance in the case of plants which produce the anthocyanin 

 but in which the formation of pigment is inhibited in the flowers. It 

 is conceivable that the materials necessary for the formation of antho- 

 cyanin are present but there is inhibition for some unknown reason. 

 The treatment with sodium amalgam may remove the cause of inhibition 

 and natural anthocyanin may be formed. Only isolation and accurate 



Journ. of Gen. iv 9 



