CHAPTER III 
MICROSCOPES FOR USE IN CHEMICAL LABORATORIES. 
The problems which the chemist is called upon to solve where 
the microscope is of great value, if not actually essential, are 
so diverse in their nature and the materials to be examined so 
varied in size, outward form, structure and composition that it 
is safe to say that no single instrument will ever be constructed 
which will meet all requirements and fulfill all conditions. Before 
deciding upon any given style or model of instrument the in¬ 
tending purchaser should, therefore, first carefully consider the 
kind of work his instrument will most frequently be called upon 
to perform. 
A microscope for microchemical analysis and applicable to 
the ordinary problems arising in the chemical laboratory should 
fulfill the following requirements: 
1. The stand should be substantially built so as to be easily 
and safely carried about. It should permit the attachment of 
the usually employed accessories, such as a mechanical stage, 
Abbe condenser, camera lucida, polarizing apparatus, etc. A 
hinged pillar allowing the inclination of the microscope is a 
valuable feature and a great convenience. In a vertical position 
for work the stand should be low enough to permit observations 
being made in comfort, without the necessity of having either 
specially high stools or low tables. It is desirable that the in¬ 
strument be entirely finished in black and have as few bright 
reflecting surfaces as possible. 
2. There should be coarse adjustment by diagonal rack and 
pinion of as great range as possible. When the movement of 
the rack is short the usefulness of the microscope is greatly 
restricted, since low powers cannot then be used with thick ob¬ 
jects. A sensitive fine adjustment is also an essential, and if the 
fine adjustment is provided with micrometer screw and gradu- 
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