344 
MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
in repeated portions of hot water, by which so much was taken up as to give a yellow 
solution. The water being poured off, the resin was dissolved in alcohol, and a por- 
tion of the filtered alcoholic solution evaporated in a thin film, and heated for sixteen 
hours at 250° Fahr. As before, it had become perfectly dry and brittle, but did not 
fuse. This resin, however, after evaporation, remains tough for a long time, and does 
not become friable till after being heated for several hours. 
12-36 grs. gave C = 25*625, and II = 9'283, or per cent., 
Carbon 57*34 
Hydrogen 8*33 
Oxygen 34-34 
100 
This result agrees so closely with those previously obtained, that we may consider 
the presence of thirty-four equivalents of hydrogen in the formula for this resin to 
be as certainly determined, as we can expect it to be, by the analysis of the uncom- 
bined resin, according to our present methods. 
XI. Resin of Labdanum. 
The resin of labdanum is said to be obtained from the Cystus Creticus, a native of 
Syria and of the Grecian Archipelago. It occurs in commerce in the form of black 
masses, more or less soft and tenacious. Alcohol rarely dissolves more than one- 
fourth of the whole mass ; the solution has a dark-brown colour, a bitter taste, and 
gives on evaporation a dark-brown transparent resin. This resin has a peculiar, not 
very unpleasant odour; having, when the resin is hot and melted, a slight resemblance 
to that of colophony*. 
1. A portion of the solution in cold alcohol (0'83) was evaporated at a gentle heat 
in a thin film, and afterwards heated for six hours to 212° Fahr. When cold the resin 
was brittle, but the fragments readily cohered when the mass was broken up. 
6*635 grs. gave C = 17*1? and H = 5*83 grs. 
2. A second portion was evaporated and kept at a temperature of 150° Fahr. for 
thirty-six hours, and afterwards for four hours at 212° Fahr. 
8-115 grs. gave C = 2T01, and H =7*185 grs. 
These results give per cent., 
l. 2. 
Carbon 71*26 71*58 
Hydrogen 9*76 9’82 
Oxygen 18'98 18*60 
100 100 
* The odour of colophony is that which is generally understood by the term resinous. 
