MICROCHEMISTRY. 149 



and may suggest how the microscope serves to test the 

 identity and the purity of organic bodies. 



5. The Methods of Systematic Microchemical Analy- 

 sis. — ^We have seen that microchemistry is a much 

 wider term than crystallography, and covers the study 

 of change, of state and of chemical reactions as well as 

 crystalline form. In this broad sense, specific micro- 

 chemical tests have been suggested by Behrens and 

 others for the detection of the elements and the various 

 acid radicles. Recently Hinrichs has prepared a com- 

 plete outline for qualitative analysis under the microscope. 

 Whether such a scheme will ever come into general use is 

 doubtful, although it promises results with a minimum 

 of time and material; but the study of two typical basic 

 and acid groups may prove suggestive to the student. 



A microburner yielding a flame not more than a quarter 

 of an inch in height must be provided for melting the 

 substances examined, and it is convenient to have the 

 lamp so small that it may be placed under the stage of 

 the microscope if desired. For ordinary work micro- 

 scopic slides are used, a drop of the substance to be tested 

 being placed thereon with a fine glass stirring-rod. The 

 reagent is added in minute quantity and is made to mix 

 with the first by means of a dry stirring-rod. For sub- 

 limation tests, two I -inch watch-glasses are used, one 

 inverted over the other, with the substance to be ex- 

 amined in the lower, and the appropriate test reagent 

 borne on the concave surface of the upper, glass. 



6. The Determination of the Metallic Elements. — ^Ac- 

 cording to the scheme prepared by Hinrichs, solutions of 



