46 
Selected Articles, 
QUINOMETRY. 
Test liquor. This is prepared by dissolving ten grammes 
of very pure powdered tannin in 190 grammes of cold dis- 
tilled water, and filtering the solution. There ought to be 
scarcely any residue. This solution contains one-twentieth 
of pure tannin ; it is colourless, or of a very light greenish 
brown. It should be kept in a well closed bottle, and be pre- 
pared but a short time before it is used. 
Each division of Decroizville's alkalimeter contains 0.47 
grains of the solution, and consequently 0.0235 grains of tan- 
nin, which corresponds to 0.0095 of quinine. Hence we 
have have only to multiply the number of divisions employed 
by this number, to ascertain the quantity of the alkaloid pre- 
sent. Suppose, for instance, that for a quantity n of cinchona, 
it requires 100 measures of the test liquor to produce a com- 
plete precipitation^ it is merely requisite to multiply 100 by 
0.0095 grains to have the quantity of quinine contained in the 
cinchona, or 100 + 0.0095 of quinine in n of bark. 
TRIAL OF CINCHONA BY THE TEST LIQUOR. 
About ten pounds of the bark to be tried, is to be taken as 
a sample, which is to be reduced to a fine powder. One 
pound of this is to be separated and treated three times with 
boiling alcohol at 32°, acidulated each time with eight 
grammes of sulphuric acid ; the tincture is to be carefully 
pressed out, and an excess of hydrate of lead added to it, till 
it becomes colourless. It is then to be filtered, and a small 
quantity of oxalate of soda or ammonia added to it, to pre- 
cipitate any lime or lead in solution in the alcohol ; the alka- 
line liquid is then to be saturated with sulphuric acid, added 
drop by drop, and the whole evaporated. The residue, 
•slightly acidulated, is to be dissolved in pure water and fil- 
tered, to separate the chlorophylline or greenish resin, and 
weighed. A tenth of it then to be treated by the test liquor, 
as above described, operating with great caution, and care- 
fully filtering towards the close of the operation, adding the 
solution of tannin as long as there is any precipitate, then ex- 
amining how many divisions of the alkalimeter are occupied. 
