Manchester Memoirs, Vol. xlvii. (1903), No. i». 3 



archil) contain a crystalline substance which he named 

 erythrin, on account of its property of yielding a red 

 colouring matter when its solution in ammonia is 

 exposed to the air. He further observed that when boiled 

 with alcohol it is converted into a different crystalline 

 substance which does not show this colour reaction, and 

 this he named pseudoerytlirin. The determination of the 

 nature of these substances was largely due to Schunck, 

 who showed that his lecanorin (lecanoric acid), when 

 boiled with alcohol, is very readily etherified, yielding a 

 substance which is evidently identical with Heeren's 

 pseudoerytlirin ; this latter substance is therefore, in all 

 probability, the ethylic ester of lecanoric acid. When 

 boiled with water, erythrin is decomposed into orsellinic 

 acid and picroerythrin — a bitter substance which had 

 already been obtained by Heeren — and, since this latter 

 substance, on hydrolysis with lime water, is converted into 

 orsellinic acid and erythrol, it follows that it is an ester 

 derived from one molecule of orsellinic acid and one 

 molecule of erythrol. The constitution of erythrin itself 

 is thus shown to be that of an ester derived from two 

 molecules of orsellinic acid and one molecule of erythrol. 



The next subject to which Schunck turned his atten- 

 tion was the investigation of the colouring principles of 

 the madder root {Rtibia tmctoruin), and in this field also 

 he obtained remarkable and important results which at 

 once attracted the attention of chemists. The madder 

 root has been employed for dyeing purposes from very 

 early times, but nothing was known as to the active 

 principle contained in it until the year 1826, when Colin 

 and Robiquet succeeded in isolating a colouring matter 

 from it, and to this they gave the name aiisariii. In 

 1828 Zenneck published a paper in which he made the 

 remarkable suggestion that the alizarin was not con- 



