188 Dr. R. D. Thomson on Parietin, a Yellmv Colounng Matter. 



COMrOSITION OF TARIETIN. 



The product of tho second solution in alcohol, when dried at 212°, 

 and burned witli oxide of copper, afforded the following result: — 



3-16 grains gave 7*376 carbonic acid. 

 1*410 water. 



This corresponds with 



31600 100- 100- 100- 



As it appeared from the preceding result that the parietin was 

 altered in its character by attempting to re-dissolve it in alcohol ; the 

 parietin, after being dissolved in alcohol from the lichen, was, after 

 the filtration of the fluid, allowed to deposit by cooling. It was then 

 thrown on a filter, and dried on a tile, and then digested in hot alcohol, 

 to remove any fatty or resinous matter with which it might be 

 contaminated. The same object may bo attained by digestion in 

 ether. The parietin was then dried at 212°, and analysed. 



2*96 grains afiforded, when burned with black oxide of copper, 



7*15 grains carbonic acid. 

 1-294 rr water. 



This is equivalent to 



Expt. 



Carbon, 1-9500 65-87 



Hydrogen, 01437 4-85 



Oxygen, ...... 0-8663 29-28 



2-9600 100* 

 and agrees with the following calculation : — 



10-25 100- 100- 



The formula, therefore, will be according to this view, 



Co H4 O3 



or we may, as in the preceding case, consider it as an oxide of an 

 oil, and the composition when calculated would be. 



