CHAPTER Jil 
MICROSCOPIC MEASUREMENTS 
In making critical examinations of powdered drugs, it is 
frequently necessary to measure the elements under observation, 
particularly in the case of starches and crystals. 
OCULAR MICROMETER 
Microscopic measurements are made by the ocular microm- 
eter (Fig. 21). This consists of a circular piece of transparent 
glass on the centre of which is etched a one- or two-millimeter 
scale divided into one hundred or two hundred divisions re- 
Fic. 21.—Ocular Micrometer Fic. 22.—Stage Micrometer 
spectively. The value of each line is determined by standard- 
izing with a stage micrometer. 
STAGE MICROMETER 
The stage micrometer (Fig. 22) consists of a glass slide upon 
which is etched a millimeter scale divided into one hundred 
equal parts or lines: each line has a value of one hundredth of 
a millimeter. 
STANDARDIZATION OF OCULAR MICROMETER WITH LOW-POWER 
OBJECTIVE 
Having placed the ocular micrometer in the eye-piece and 
the stage micrometer on the centre of the stage, focus until 
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