42 Mr. Brande’s observations on an astringent 
according to the process recommended by Sir H. Davy, and 
the gallate of barytes was subsequently decomposed by dilute 
sulphuric acid ; I found it, however, impossible to obtain the 
gallic acid in a free state, on account of the facility with which 
it was decomposed on attempting to evaporate the solution. 
When lime water is added to the aqueous infusion of the 
galls, a copious insoluble precipitate is formed, consisting of 
tannin and lime, and a gallate of lime remains in solution, 
which is decomposed by oxalic acid. In this way I succeeded 
in procuring the gallic acid nearly pure. 
I boiled some pure caustic lime in a strong infusion of the 
galls, and when cold, filtered the mixture : oxalic acid was 
added as long as it produced a precipitate in the filtered 
liquor, heat was applied, and after separating the oxalate of 
lime, a solution of nearly pure gallic acid was obtained. 
I have failed in all these experiments in obtaining the gallic 
acid perfectly pure, but the Chinese galls appear to me to 
offer a most promising source of that acid in its pure state, 
and the gallates obtained by the processes above described, 
seem to be entirely free from extractive matter and to 
approach nearer to pure salts, than those which are procured 
from infusions of the common galls. 
When the Chinese galls are exposed in a glass retort to the 
heat of an Argand lamp', a considerable quantity of gallic acid 
tainted by empyreumatic oil, rises into the neck of the ves- 
sel, and if the heat be continued, the water which is produced 
dissolves it, and carries it over into the receiver : during 
destructive distillation, therefore, a considerable portion of 
liquid gallic acid may be thus obtained. 
One hundred grains of the galls in powder, were submitted 
