146 ELEMENTS OF APPLIED MICROSCOPY. 
3. The Detection of Quinin.—It has been noted that 
one of the earliest and most profitable applications of 
microchemistry has been made in the study of drugs 
and poisons; and the toxicologist depends to a great 
extent upon various specific microchemical tests. Hera- 
path’s method for the detection of quinin, applied par- 
ticularly to the examination of the urine of patients 
under quinin treatment, may be studied as an example. 
It depends on the formation of characteristic crystals 
of the iodosulphate of quinin on the addition of tinc- 
ture of iodin to an alcoholic solution of the drug. In 
practice, the urine to be analyzed is neutralized and shaken 
out with ether. The ethereal solution is evaporated and 
the residue dissolved in a mixture of 12 cc. of glacial 
acetic acid and 4 cc. of 95% alcohol, to which 7 drops 
of dilute sulphuric acid (1 gram of strong sulphuric acid 
with 9 grams of water) have been added. A very minute 
drop of tincture of iodin added to this solution first pro- 
duces, if quinin be present, a cinnamon-yellow spot, 
due to the reaction of the iodin and quinin. Next the 
alcohol separates in little drops, driving the fluid away 
from the center of the preparation. Finally, the acid 
liquid flows back again, and thin, greenish plates of the 
iodosulphate appear, often arranged in beautiful rosette 
forms. The crystals produce strong polarizing effects, 
and turn brownish red when heated. 
3. The Separation of Related Organic Substances.— 
The most important aid which the microscope can offer 
to the chemist lies in the domain of organic analysis. 
Lehmann even goes so far as to say that “ Crystallography 
