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Selected Articles. 
loid can be separated from this precipitate by means of alco- 
hol ; but it often happens that this alkaloid is in very minute 
quantities, and moreover is slightly soluble in water, or be- 
comes so under the influence of the precipitating agent : final- 
ly, as it is necessary to concentrate the solution to obtain the 
desired product, there may also be a loss from the reactions, 
caused by heat, or the formation of mucilaginous matters, 
which render the solution so viscid, as to greatly retard the 
complete separation of the precipitates. These obstacles are 
constantly met with, and are the frequent cause of want of 
success in these operations. The property of tannin of pro- 
ducing salts with vegetable alkalies, almost insoluble in cold 
water, may remedy these inconveniences, by permitting all 
the alkaloid to be concentrated in the precipitate. 
Method. — The powdered vegetable, (roots, leaves or fruit,) 
its extract, or what I prefer, the juice of the fresh plant, is to 
be treated with warm water, slightly acidulated by means of 
sulphuric acid. The clear liquid obtained after expression is 
to be permitted to cool, and then almost neutralized by potash, 
soda or ammonia ; and, finally, a concentrated infusion of nut 
galls, or of oak bark added as long as any precipitate takes 
place. The precipitate is to be collected on a linen cloth, 
washed with cold water, drained and pressed till it becomes 
of a pasty consistence. In this state the precipitate is to be 
mixed as exactly as possible with a slight excess of pulver- 
ized slacked lime. A green or bluish colour is produced, which 
soon changes to a reddish brown, then the magma is to be 
dried on a water bath, till it becomes pulverulent. In this state 
it is to be treated with hot alcohol, or sulphuric ether, which 
have no action on the calcareous tannate, and after distillation 
of the filtered liquor, a product is obtained containing the al- 
kaloid. By exposing this to the air, it generally crystallizes in 
a few days, but it is often advantageous to saturate it as ex- 
actly as possible with phosphoric or sulphuric acid before it 
is left to crystallize. If crystals or a granular gelatinous 
mass is obtained, they are to be collected on a linen cloth, 
and after being slightly expressed, are to be purified by an- 
other crystallization. The alkaloid is now to be isolated in the 
