280 
ELEMENTARY CHEMICAL MICROSCOPY 
the latter down at a suitable point. As soon as the proper 
volume of liquid has been drawn off, still holding the slide 
inclined, a piece of filter or folded lens paper is drawn through the 
channel, between the two drops at C, Fig. 146, and the prepara¬ 
tion immediately heated gently over the micro-flame at this 
same point. The result of this heating is the separation of the 
two drops by a dry space; thus there is no danger of the decanted 
liquid flowing back when the slide is again placed in a horizontal 
position. 
Fig. 146. Decanting a Drop of Liquid from a Precipitate. 
When the clear decanted liquid is not wanted for analysis and 
only the sediment, or precipitate, in the original drop is to be 
utilized, the decanted portion and connecting stream are both 
wiped off the slide with filter paper while the slide is inclined and 
the preparation heated gently below the wiped-off drop to pre¬ 
vent any farther spreading. 
In cases where the sediment in the drop persists in flowing with 
the liquid being drawn off, and where heating is not objection¬ 
able, the slide is tipped so as to cause all the liquid to again flow 
back into the original source and the drop is evaporated to dry¬ 
ness at a low temperature, exceptional care being taken to pre¬ 
vent heating the residue after evaporation. This step will 
usually cause the sediment to cling to the glass and to aggluti¬ 
nate. A drop of water or the proper liquid is then carefully 
added, the preparation allowed to stand a few seconds to permit 
the soluble compounds to pass into solution and the solution 
then decanted as above described. Usually a clear liquid may 
now be obtained without difficulty. 
