220 ELEMENTARY CHEMICAL MICROSCOPY 



Lehmann 1 long ago pointed out that this method of " fusion 

 testing" could be made use of in qualitative analysis but the 

 interpretation of the phenomena which may be observed, usu- 

 ally requires a profound knowledge of chemistry and much 

 practice in manipulation. 



In the Appendix will be found a table giving the melting points 

 of compounds which can be employed in making estimations of 

 melting points by the process described above. 



Method B. (Exact.) Melting points below the boiling point 

 of water may be determined with great accuracy by means of 

 a hot stage through which hot water is made to circulate. A 

 convenient form of apparatus is shown in Fig. i32. 2 It consists 



FIG. 132. Apparatus for the Determination of Low Melting Points. 



of a glass box or trough, such as is commonly employed for the 

 spectroscopic examination of liquids, the open end of which is 

 provided with a wedge-shaped piece of rubber, forming a tight 

 stopper. The hot water enters the cell through the glass tube A 

 and escapes at B, the rate of flow being controlled by a stop- 

 cock or screw-clamp. The hot water may conveniently be ob- 

 tained by siphoning it through a small coil of copper pipe D 

 heated by a Bunsen burner E. Or the heating system devised 

 for providing a continuous flow of hot water through a Zeiss 



1 O. Lehmann, Die Krystallanalyse, Leipzig, 1891. 



2 Chamot and Albrech, Unpublished paper presented to the Cornell Section, 

 Am. Chem. Soc.; May, 1906. 



