2 Perkin, Chemical Researches of Edzvard Schunck. 



In the memoir just mentioned, Schunck succeeded in 

 isolating from the lichens of the Lecaftora and Variolaria 

 section, which he was then investigating, a crystalline 

 substance which he named lecanorin. Although accurate 

 organic analysis was a matter of considerable difficulty 

 in those days, he was nevertheless successful in correctly 

 determining the composition of this important substance, 

 and the formula Ci6Hi407 + 2H20 which he gave to 

 lecanorin has been repeatedly confirmed, and is the one 

 in use at the present day. 



Rochleder and Heldt, who soon afterwards (in 1843) 

 obtained the same substance from Evernia prunastrt, 

 altered the name to lecanoric acid in order to indicate 

 that it was an acid, and subsequently it was shown by 

 Stenhouse, Hesse, and others, that Schunck's lecanorin 

 is very widely distributed, and occurs as an important 

 constituent of many of the principal lichens. A definite 

 clue to the constitution of lecanoric acid was obtained 

 through the observation of Stenhouse that this substance 

 is hydrolysed on boiling with water and converted into 

 two molecules of orsellinic acid, a decomposition which 

 clearly proves that the constitution of the acid is repre- 

 sented by the formula 



OH CO„H OH 



<^>-o.co-<-> 

 c'h., oh 



CH, 



But the isolation of lecanorin was not the only im- 

 portant discovery which Schunck made in the course of his 

 researches on the lichens. Heeren (in 1830) had made 

 the observation that the lichens Roccella tinctoria and 

 Lecanora tartarea (which were at that time, and indeed 

 are now, largely used in the preparation of litmus and 



