352 
MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
the loss of the hydrogen being to that of the oxygen as 5 : 4, while in the resin they 
exist in the proportion of 8*3 to 3. 
This resin is easily fusible, and like the Berengela and assafcetida resins, runs into 
a mass in the bottle in which it is kept. The alcoholic solution gives, with a similar 
solution of acetate of lead, a white precipitate, but I have not as yet analysed any of 
its salts. 
XV. Resin of Opoponax. 
The green resin of opoponax, treated with common alcohol, gives a pale brownish- 
red solution, from which, by evaporation, a transparent brown resin is obtained 
having a peculiar odour, fusing readily at 212° Fahr. ; and after being kept at that 
temperature for a short time, becoming brittle when cold. The residue from the 
natural resin, after being treated with alcohol, gives with boiling water a solution 
which passes milky through the filter. Both solutions have a bitter taste, accom- 
panied by a peculiar flavour. The matter which remains insoluble in alcohol or 
water consists chiefly of woody fragments, and is nearly equal in bulk to the natural 
gum resin originally experimented upon. 
The resin extracted by alcohol is decomposed by a comparatively low temperature, 
and requires therefore to be treated with considerable care, when prepared for the 
purpose of analysis. 
This is shown by the following experiments. 
1 . A small portion of the alcoholic solution was evaporated at a gentle heat, which, 
when the resin was nearly free from alcohol, was raised to 212° Fahr. It was kept 
at this temperature for two hours, but from the inclination of the shallow vessel a 
considerable portion of the resin (the whole not exceeding 10 grs.) had run together 
into a mass. On cooling, this latter portion did not harden. The brittle portion was 
scraped off the dish, and burned with oxide of copper. 
7*5 grs. gave C = 17*14, and H = 4*52 grs. 
2. A second portion of the alcoholic solution was evaporated at 150° Fahr., and the 
resin, in the state of a very* thin film, was kept twelve hours at a temperature not ex- 
ceeding 180° Fahr. Previous to analysis the heat was raised for one hour to 212° 
Fahr. The resin was very brittle, in thin fragments, was of a pale brown colour, and 
preserved the characteristic odour. 
7*995 grs. gave C = 18*55, and H = 4*785 grs. 
3. A third portion being evaporated at a gentle heat was fused for two hours at 
212° Fahr. 
7*62 grs. gave C = 17*64, and H = 4*633 grs. 
4. The resin of a fourth portion, after long exposure to a gentle heat, was fused for 
a few minutes at 250° Fahr. 
7*69 grs. gave C = 18*05, and H = 4*61 grs. 
* A grain of the resin being spread over at least a square inch of surface. 
