If tannin exist in the first solution made by cold 
water, its separation is easily effected by the pro- 
cess described page 84. The solution of isin- 
glass must be gradually added, to prevent the ex- 
istence of an excess of animal jelly in the solution, 
which might be mistaken for mucilage. 
When the vegetable substance, the subject of 
experiment, will afford no more principles to cold 
water, it must be exposed to boiling water. This 
will unite to starch, if there be any, and may like- 
wise take up more sugar, extract, and tannin, pro- 
vided they be intimately combined with the other 
principles of the compound. 
The mode of separating starch is similar to that 
of separating mucilage. 
If after the action of hot water any thing remain, 
the action of boiling alcohol is then to be tried. 
This will dissolve resinous matter ; the quantity of 
which may be known by evaporating the alcohol. 
The last agent that may be applied is ether, 
which dissolves elastic gum, though the application 
is scarcely ever necessary ; for if this principle be 
present, it may be easily detected by its peculiar 
qualities. 
If any fixed oil or wax exist in the vegetable 
substance, it will separate during the process of 
boiling in water, and may be collected. Any sub- 
stance, not acted upon by water, alcohol, or ether, 
must be regarded as woody fibre. 
If volatile oils exist in any vegetable substances, 
it is evident they may be procured, and their quan- 
tity ascertained by distillation. 
When the quantity of fixed saline, alkaline, me» 
