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. 132. 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2 Chamot and Albrech, Unpublished paper presented to the Cornell Section, 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. 



