252 Mr. Davy’s Experiments and Observations 
III. EXPERIMENTS AND OBSERVATIONS ON CATECHU OR TERRA 
JAPONICA. 
The extract called catechu is said to be obtained from the 
wood of a species of the Mimosa,* which is found abundantly 
in India, by decoction and subsequent evaporation. 
There are two kinds of this extract ; one is sent from Bom- 
bay, the other from Bengal ; and they differ from each other 
more in their external appearance than in their chemical com- 
position. The extract from Bombay is of an uniform texture, 
and of a red-brown tint, its specific gravity being generally 
about 1.39. The extract from Bengal is more friable, and less 
consistent ; its colour is like that of chocolate externally, but, 
when broken, its fracture presents streaks of chocolate and of 
red-brown. Its specific gravity is about 1.28. Their tastes are 
precisely similar, being astringent, but leaving in the mouth a 
sensation of sweetness. They do not deliquesce, or apparently 
change, by exposure to the air. 
The discovery of the tanning powers of catechu, is owing to 
the President of the Royal Society, who, concluding from its 
sensible properties that it contained tannin, furnished me, in 
December, 1801, with a quantity for chemical examination. 
In my first experiments, I found that the solutions of catechu 
copiously precipitated gelatine, and speedily tanned skin ; and, 
in consequence, I began a particular investigation of their 
properties. 
The strongest infusions and decoctions of the two different 
kinds of catechu, do not sensibly differ in their nature, or in 
their composition. Their colour is deep red-brown, and they 
* SeeKERR. Medical Observations, Vol. V. page 155. 
