350 
MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
With this formula, the results of the first four analyses are accordant within the 
limits of the errors of manipulation. In the fifth analysis there is a large excess of 
carbon, obviously due to decomposition caused by the prolonged fusion. 
The analyses previously published gave the following results : 
After prolonged heating at 212° Fahr. 
Carbon 7686 
Hydrogen 875 
Oxygen 14'39 
After fusion at 300° Fahr. 
77-41 
8-51 
14-08 
100 
100 
In both of these the carbon is in excess, though in neither is the excess so great as 
in the fifth analysis above given. It is, however, to be ascribed to the same cause, 
namely, to partial decomposition, though not carried so far. 
From the above experiments, therefore, it appears, 
1 . That this resin, like many others we have examined, may be perfectly dried by 
heating at 200° Fahr. in the state of a thin film without being melted. 
2. That when thus dried it may be represented by C 40 H 27 0 6 ; and 
3. That when fused it rapidly decomposes, the per centage of carbon increasing, 
while that of hydrogen remains nearly stationary. The analysis E. gave 
C 40 H 27 0 5 gives 
Carbon 78"08 7 8’51 
Hydrogen 870 8’65 
Oxygen 13-22 12-84 
100 100 
So that by prolonged heating at the melting point the formula C 40 H 27 0 6 gradually 
approximates to C 40 H 27 0 5 , which, as will appear in a subsequent part of this paper, 
is identical with the change which heat produces on some other resins, as the resin of 
assafcetida. 
4. Salts of this resin . — In the paper to which I have already referred I have shown 
that an alcoholic solution of this resin precipitates similar solutions of nitrate of silver 
and of acetate of lead. The salt of silver appears to be represented by 2 A g O + 
(C 40 H 27 o 6 ). 
XIV. Ammoniac Resin. 
I. When the ammoniac resin of the shops is digested in cold alcohol, it undergoes 
little alteration in bulk, but a pale yellow solution is obtained, which on evaporation 
in a thin film at 150° Fahr. gives a transparent nearly colourless resin, having the 
characteristic odour of the natural product. Heated to 212° Fahr. for some time, 
the resin assumes a yellow colour, which gradually deepens, while at the same time 
the peculiar odour becomes less intense. After heating for forty-eight hours at 180° 
Fahr., and afterwards for several hours at 212° in a thin film. 
