MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
377 
A. 7*575 grs. of pure resin, gave C = 20-28 grs., and II = 6-245 grs. 
B. 7-475 grs. of pure resin, heated at 200° Fahr. for a longer period, gave 
C = 19-76 grs., and H = 6-09 grs. 
C. 7*166 grs. of pure resin still longer heated, gave C = 18-30, and H = 5-705 grs. 
D. 7"325 grs. of pure resin, heated twenty-four hours longer than C., gave C = 19 - 02, 
and H = 6-073 grs., or per cent., 
A (19). 
Carbon 74"03 
B (20). 
73-09 
C (21). 
70-61 
D (22). 
71-80 
Hydrogen 9" 16 
9-05 
8-84 
9-21 
Oxygen 16-81 
17*86 
20-55 
18-99 
100 
100 
100 
100 
Though longer heated, the portion D. had not been so much changed as the portion 
C. There is no question of comparative purity in this instance, since all the portions 
were obtained from the same solution. The differences, if not errors of analysis, are 
due to the action of heat alone, and the discordant results serve to show how very 
much a resin may be changed by prolonged heating, at a temperature far below that 
at which it melts, which in the present case was never approached. 
If we compare the result A. with the constitution of the small quantity of the 
second resin obtained by the action of quicklime (p. 375, analysis 14.), we find them 
to be nearly identical ; and as the resin of analysis A. (19.) had been long heated at 
200° Fahr., I am inclined to think that first portion to have been most nearly in the 
normal state of the resin, and that the differences observed in the constitution of the 
other portions are due to the evolution in greater or less quantity of that volatile oily 
product, which I have already described as given off when the resin of analysis 14 
was heated to a temperature approaching that at which it began to cohere. 
From this imperfect examination of the action of caustic potash on the crude 
benzoin, I conclude that, under the circumstances above-detailed, it was separated 
into benzoic acid and two resins, of which the one is represented by C 40 H 22 0 9 (ana- 
lyses 17 and 18), and the other by C 40 H 30 0 7 (analysis 19). 
This second resin, by prolonged heating, gives off a volatile fluid, by which its 
constitution is gradually altered, becoming successively C 40 II 30 0 8 , and C 40 H 30 0 9 . 
The conformity of the analytical results with these formulae is shown by the follow- 
ing tabular comparison : — 
c 40 H 30 °7 g^es 
Found analysis (19). 
C 4 o H 30 °s gives 
Found analysis (22). 
C 40 H 30 0 9 gives 
Found analysis (21). 
Carbon 73*99 
74*03 
72-25 
71-80 
70-58 
70-61 
Hydrogen 9*07 
9-16 
8-84 
9-21 
8-64 
8-84 
Oxygen 16‘94 
16-81 
18-91 
18-99 
20-78 
20-55 
100 
100 
100 
100 
100 
100 
To produce this change of constitution, it is only necessary that a carbo-hydrogen, 
mdcccxl. 3 c 
