130 
ON GAMBOGE. 
i. 
ii. 
Carbon, 
71.87 
72.22 
Hydrogen, 
7.06 
7.41 
Oxygen, 
21.07 
20.37 
100.00 
100.00 
To determine the atomic weight of the acid, the salts of 
silver, lead, and barytes were subjected to analysis. The 
results were as follows: — 
Salt of Silver, Ceo H 35 0i 2 + Ag 0. 
Salt of Lead, 2 Coo H 35 12 + 5 Pb 0. 
Salt of Barytes, 4 C 60 H 35 O i2 + 3 Ba 0. 
Johnston found, in 100 parts of the resin of gamboge in 
the uncombined state: 
Carbon, 71.70 
Hydrogen, 7.0^ 
Oxygen, 21.27 
Whence he calculated the formulae, C40 H 23 9 and C 4 s H 24 
O10, which give, with the metallic oxides, results varying 
but little from those deduced from the above analysis. 
After extracting the resin of gamboge by aether, the resi- 
due was digested in pure alcohol, the result of which was a 
glutinous substance, which on distillation left a glutinous 
brown extract, soluble in water, a property distinguishing 
ii from the fatty acid extracted by aether. It exists but in 
very small proportions. The residue, remaining after the 
treatment of gamboge with aether and alcohol, when boiled 
in water, left only impurities of wood and sand mixed with 
the gamboge of commerce; whilst the solution, on account 
of its mucilaginous properties, would not pass through a 
filter. Diluted with water and drawn off by a syphon, the 
fluid was concentrated by evaporation. The gum thus ob- 
tained was digested and washed with spirit until it was 
