THE CHEMISTRY OF CHLOROPHYLL 433 



of Schunck and Marchlewski, neither the alkachlorophyll nor 

 phylloxanthin was obtained in a satisfactory crystalline form, 

 nor could either lay claim to anything more than approximate 

 purity. Nor did the earlier researches throw any light on the 

 changes undergone by the original pigment when treated with 

 alkalis and acids. Furthermore, it is not by any means proved 

 that the crystalline products obtained by the earlier investi- 

 gators were homogeneous products, in spite of their crystalline 

 form. 



Phytochlorins and Phytorhodins. — Willstatter, by the intro- 

 duction of a new method of purification, has shown that by the 

 action of acids and alkalis on chlorophyll a variety of products 

 can be obtained, which can be separated from one another by 

 a fractional extraction of their ethereal solutions by graded 

 strengths of acids. By varying the conditions of experiment, 

 different quantities of these products could be obtained. Two 

 main groups of products were obtained. One of these groups 

 consisted of products which yielded in indifferent solvents, 

 olive green to green solutions, whereas the other, obtained 

 mainly from alkachlorophyll, by the action of alcoholic hydro- 

 chloric acid, was composed of the substances which in acid 

 solutions were of blue to green colour, while in neutral solvents 

 they were a brilliant red. The products belonging to the former 

 of these groups were termed the phytochlorins, whereas the latter 

 were called phytorhodins. The substances belonging to these 

 classes were insoluble in water, but more or less soluble in 

 organic solvents. They were weak acids, soluble in alkalis, 

 even in ammonia, and bicarbonate, but could be quantitatively 

 extracted from such solutions by ether. The various members 

 of the groups could, however, be differentiated by their varying 

 basic characters. Some of them could be readily extracted from 

 their ethereal solution by means of weak hydrochloric acid, and 

 were consequently of somewhat marked basic character, whereas 

 others required acid of much higher concentration for their 

 extraction ; in these the basic character was consequently much 

 less marked. Upon these differences in the basicity, Willstatter's 

 method of separation was founded. As an example of the 

 employment of the method, the following experiment may be 

 quoted : 200 grams of extract obtained from 9 kilos of stinging- 

 nettle leaves were dissolved in 2 kilos of 96 per cent, spirit, and 

 so much sodium hydroxide solution added as to make a 2 per 



