HANDLING SMALL AMOUNTS OF MATERIAL; DISTILLATION 293 
thumb and forefinger, place a cooling drop of water upon the top 
of the slide and heat the watch glass gently over a micro-flame 
(Fig. 152) until vapors begin to con- __ 
dense upon the object slide. Heating 
to violent boiling must be avoided. 
The cooling drop upon the upper sur¬ 
face of the object slide is removed, 
the slide raised from the watch glass 
and turned over with a quick move¬ 
ment. The proper reagents for dis¬ 
closing the presence of the constituent 
being sought are added and the resulting preparation examined 
with the microscope. 
The method just described is applicable only to easily vola¬ 
tilized substances and where prolonged heating is unnecessary, 
but even in expelling ammonia, the fingers become uncomfort¬ 
ably hot. To avoid this discomfort the distilling device shown in 
Figs. 153 and 154 may be employed. It consists of a tiny glass 
Fig. 152. Watch-glass Method 
of Distillation. 
Fig. 153. Apparatus for Microchemical Distillations. (Slightly Enlarged.) 
crucible C, whose upper edge is ground smooth and true, a sup¬ 
porting clamp made of spring brass wire W and an ordinary 
short object slide O. The component parts are shown in Fig. 
154, and the apparatus in use in Fig. 153. Just as in the watch 
glass method fibrous asbestos or glass wool is employed as an 
absorbent, an acidulated or alkaline drop serves to retain the 
volatile constituent and a cooling drop is placed upon the upper 
surface of the condensing slide. A lever L serves to keep the 
