42 
Selected Articles. 
ART. XIII.— APPLICATION OF TANNIN AS AN ALKALOIMETER. 
By O. Henry. 
By Alkaloimetry is meant, processes calculated to show in 
an exact manner, the quantities of alkaloids contained in cer- 
tain vegetables. This, which in general has only been ac- 
complished by long and complicated processes, which are at- 
tended with many inconveniences, from the tediousness of the 
operation, and the repeated decompositions and evaporations 
they require, hence always exposing the operator, particularly 
when experimenting on a small scale, to a loss of a certain* 
quantity of the product. Having been several times called 
upon to determine the richness of different parcels of cinchona 
in alkaloids, I have been forcibly impressed with the difficul- 
ties above alluded to, and have made many experiments to 
ascertain a more expeditious method of obtaining the desired 
ends. Thus, wishing to proceed as in alkalimetry, I thought 
of precipitating the quinine and cinchonine by a liquid of 
known strength, and the quantity of which would be appre- 
ciable by the divisions of a graduated measure. Taking ad- 
vantage, with this view, of the property pointed out by Serul- 
las, possessed by iodic acid of forming insoluble precipitates 
with almost all the alkaloids dissolved in alcohol, I thought I 
should obtain my end, by adopting a solution of pure iodic 
acid, supposing that an alcoholic solution of quinine &c. would 
require certain proportion of this test to produce its entire 
precipitation ; but this method did not succeed, because on 
the one hand, if the alkaloid solution was made with alcohol 
at 32°, a part of the iodic acid was itself precipitated in an 
uncombined state, and if made with that fluid at 22°, «a por- 
tion of the organic acid iodate remained in solution. 
Since the discovery of the vegetable alkalies and the happy 
application of many of them in medical practice, their extrac- 
tion has become a branch of commercial industry. This, 
which is of French creation, and for a long time peculiar to 
our laboratories, is now of sufficient importance to require 
some means by which the value of the raw materials em- 
