222 ELEMENTARY CHEMICAL MICROSCOPY 
Any flat surfaced, stoppered’container may serve as a hot 
stage, as, for example, a small flat bottle. 
For temperatures above 150° C. the only convenient and uni¬ 
versally applicable heating system is by means of an electric 
current, resistance wire and suitable rheostat. The heating 
coil in this case may consist of manganin, nichrome or platinum 
wire. To obtain the best and most reliable results part of the 
heating coil should be above the object being heated and part 
below. 
Fig. 134 shows an electrically heated hot stage which has 
been in use in the author’s laboratory for several years. It 
Eig. 134. Apparatus for the Determination of Melting and Subliming Points. 
consists of a low cylinder of ‘‘Alberene stone” closed at the top 
and bottom by thin glass, or by mica when high temperatures 
are employed. The heating coil H, H consists of fine platinum 
wire wound in fine coils. In the illustration A shows the Alberene 
stone; B, brass guides for the object slide acting as cover; C, 
adjustable wire fingers for supporting cover glasses, tiny crucibles, 
“micro” retorts, etc., D is a removable, thin brass diaphragm 
cutting down the opening of the stage and serving as a radiator; 
T, thermometer; PP, binding posts; M, mica or glass window 
closing the bottom of the hot stage; and S, the object slide cover. 
The method of inserting the hot stage for use in place of the rotat¬ 
ing stage is shown in Fig. 135. By attaching an Abbe camera 
lucida to the microscope tube and properly tipping the mirror, 
the image of the scale of the thermometer may be so reflected 
as to be seen alongside of the material whose melting point is 
