CHAPTER XII. 
METHODS FOR THE HANDLING OF SMALL AMOUNTS OF 
MATERIAL. 
Microchemical Methods. — By microchemical methods we 
generally mean the application of chemical operations to the 
examination and study of very small quantities of material. The 
chief chemical operations with which we have to deal are: i. 
Solution; 2. Decantation; 3. Filtration; 4. Subhmation; 5. 
Distillation; 6. Precipitation; 7. Ignition, Fusion, and Mis¬ 
cellaneous Treatments. 
Since success in chemical microscopy requires skill in the 
technique of these operations each one will be discussed at 
length. 
I. Solution. Testing for Solubility. — At the corner of a 
perfectly clean object slide of glass, quartz, or celluloid, place a 
small drop of water (or other solvent); the drop should be 3 to 4 
millimeters in diameter and about i millimeter deep. Place 
close to this drop a tiny fragment of the material whose solu¬ 
bility is to be tested. Transfer the glass slip to the stage of the 
microscope and focus with a low power objective upon the edge 
of the drop nearest the fragment. See that the illumination, 
using an Abbe condenser, is carefully adjusted, and that the iris 
diaphragm is at least two-thirds closed. By means of a glass 
rod drawn out fine, a platinum wire or a stiff hair, slowly push 
the fragment into the drop, at the same time looking into the 
instrument so as to be able to note the phenomena which may 
take place the instant the material enters the solvent; for ex¬ 
ample, the substance may merely “melt” away, or it may de¬ 
crepitate, or give off bubbles of gas, or it may dissolve with 
decomposition (hydrolise), etc. A little practice is often neces¬ 
sary to enable the beginner to push substances into drops of 
solvent while looking into the instrument. It is of course 
276 
