220 
ELEMENTARY CHEMICAL MICROSCOPY 
Lehmann^ 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 
* O. Lehmann, Die Krystallanalyse, Leipzig, 1891. 
2 Chamot and Albrech, Unpublished paper presented to the Cornell Section, 
Am. Chem. Soc.; May, 1906. 
