on the constituent Parts of astringent Vegetables. 257 
soluble in water than the tanning principle ; and, when a small 
quantity of water is used to a large quantity of catechu, the 
quantity of tannin taken up, as appears from the nature of the 
strongest infusion, is very much greater than that of the extrac- 
tive matter. 
The extractive matter is much more soluble in warm water 
than in cold water; and, when saturated solutions of catechu 
are made in boiling water, a considerable quantity of extrac- 
tive matter, in its pure state, falls down, as the liquor becomes 
cool. 
The peculiar extractive matter of the catechu may be like- 
wise obtained, by repeatedly lixiviating the catechu, when in 
fine powder, till the fluids obtained cease to precipitate gelatine ; 
the residual solid will then be found to be the substance in 
question. 
The pure extractive matter, whether procured from the 
Bombay or Bengal catechu, is pale, with a faint tinge of red- 
brown. It has no perceptible smell ; its taste is slightly astrin- 
gent; but it leaves in the mouth, for some time, a sensation of 
sweetness, stronger than that given by the catechu itself. 
Its solution in water is at first yellow-brown ; but it gains a 
tint of red by exposure to the air. Its solution- in alcohol does 
not materially change colour in the atmosphere ; and it is of an 
uniform dull brown. 
The extractive matter, whether solid or in solution, was not 
found to produce any change of colour upon vegetable blues. 
It became of a brighter colour by the action of the alkalis ; but 
it was not precipitated from its solution in water by these bodies, 
nor by the alkaline earths. 
MDCCClil. L 1 
