146 ELEMENTS OF APPLIED MICROSCOPY. 



3. The Detection of Qtiinin. — 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 (i 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 qumin. 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 appe3.r, 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 



