258 Mr. Davy’s Experiments and Observations 
The aqueous solution of it, when mixed with solutions of 
nitrate of alumine and of muriate of tin, became slightly turbid. 
To nitrate of lead, it gave a dense light brown precipitate. 
It was not perceptibly acted upon by solution of gelatine; 
but, when solution of sulphate of alumine was added to the 
mixture of the two fluids, a considerable quantity of solid matter, 
of a light brown colour, was immediately deposited. 
To the solution of oxygenated sulphate of iron, it communi- 
cated a fine grass-green tint; and a green precipitate was de- 
posited, which became black by exposure to the air. 
It was not precipitated by the mineral acids. 
Linen, by being boiled in the strongest solution of the ex- 
tractive matter, acquired a light red- brown tint. The liquor 
became almost colourless ; and, after this, produced very little 
change in the solution of oxygenated sulphate of iron. 
Raw skin, prepared for tanning by being immersed in the 
strong solution, soon acquired the same kind of tint as the linen. 
It united itself to a part of the extractive matter; but it was not 
rendered by it insoluble in boiling water. 
The solid extractive matter, when exposed to heat, softened, 
and became darker in its colour, but did not enter into fusion. 
At a temperature below that of ignition, it was decompounded. 
The volatile products of its decomposition were, carbonic acid, 
hydrocarbonate,, and water holding in solution acetous acid and 
a little unaltered extractive matter. There remained a light and 
very porous charcoal. 
In considering the manner in which the catechu is prepared, 
it would be reasonable to conclude, that different specimens of 
that substance must differ in some measure in their composition, 
