Action of Tannin on Organic Salifiable Bases, fyc. 227 
appeared to me, would answer this end, and form a good 
alcaloimeter. 
Some months since I laid the details of this plan before the 
Society of Pharmacy, (sec Journal of Pharmacy, 1834,) and 
which I will briefly recapitulate: it is founded on the almost 
total insolubility of the compounds of tannin and cinchonine 
or quinine in cold water, and consists in adding, by means of 
the graduated test glass of Descroizilles, a solution of known 
strength of perfectly pure tannin, to a neutral solution of the 
cinchona alkaloids, perfectly free from the red colouring mat- 
ter, as well as from magnesia and lime. The number of de- 
grees required to produce complete precipitation, enables the 
operator to judge of the quantity of these organic bases, for 
it has been shown that 100 grammes of quinine or cinchonine, 
are perfectly precipitated by 250, 63 or 268 grammes 18c. of 
pure tannin. 
To return to the subject under consideration. I had re- 
marked that the tannin, in precipitating the vegetable alkalies, 
produced very large, white, caseous compounds, and for the 
most part almost insoluble in cold water; I had, moreover, 
observed, when potash, soda, lime or ammonia are employed 
to isolate them, that they become diminished or altered in a 
marked manner. Tannin, on the contrary, produced abundant 
precipitates from solutions on which the above substances had 
no effect. 
When to an aqueous solution of pure tannin, or of extract 
of nut galls, or of any other liquid containing tannin, a some- 
what acidulated solution of an organic alkali is added, there 
will be an immediate formation of a white, flocculent preci- 
pitate. This phenomenon takes place with the alkaloids in a 
more or less marked degree. 
If the solution of tannin be replaced by one of pure gallic 
acid, previously left in contact with gelatine for twelve hours, 
no distinct precipitation takes place. 
The following table shows the effects produced by solutions 
of pure tannin and gallic acid on the vegetable alkalies. 
