Ift4 Dr Thomson on Parietin^ 



the substance as at first obtained, assumes the aspect of a 

 brownish yellow powder. 



COMPOSITION OF PARIETIN. 



The product of the second solution in alcohol, when dried at 

 212°, and burned with oxide of copper, afforded the following 

 result : — 



3.16 grains gave 7.376 carbonic acid. 

 1.410 water. 

 This corresponds with 



Expt. Atoms. Calcula. Atoms. Calcula. 



Carbon, . 2.0116 63.65 40 63.82 40 62.51 

 Hydrogen, 0.1566 4.95 16 4.25 16 4.16 



Oxygen, . 0.9918 31.40 15 31.93 16 33.33 



3.1600 100. 100. 100. 



As it appeared from the preceding result that the parietin 

 was altered in its character, by attempting to redissolve 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 be attained by digestion in ether. The 

 parietin was then dried at 212°, and analysed. 



2.96 grains afforded, when burned with black oxide of copper, 

 7-15 grains carbonic acid. 

 1.294 ... water. 



This is equivalent to 



Expt. 



Carbon, 1.9500 65.87 



Hydrogen, 0.1437 4.85 



Oxygen, 0.8663 29.28 



2.9600 100. 

 and agrees with the following calculation : — 



Calculation. Expt. 



Carbon, . . .75 X 9 = 6.75 65.85 65.87 



Hydrogen, . .125x4= .5 4.87 4.85 



Oxygen, . . 1. x3 = 3.0 29.28 29.28 



10.25 100. 100. 



