QUANTITATIVE MICROSCOPIC DETERMINATIONS 161 



approximately of the magnifying power, the results would be inac- 

 curate. In order that the work of different analysts may be unified, 

 it is necessary to adopt standard methods. The surface area of the 

 field of view of each microscope used must be accurately determined 

 by means of the stage micrometer. The Bureau of Chemistry method 

 for the examination of tomato products directs that the field of view 

 be unified by means of the draw tube, so that each field shall equal 

 1.50 sq. mm. (diameter of field of view equals 1.382 mm., therefore, 

 area of field equals 1.50 sq. mm.). This method is faulty because 

 no allowance is made for the differences in magnification of the micro- 

 scopes used. Proper adjustment of this kind should be made by means 

 of the ocular diaphragm, after having reduced the microscopes to the 

 same magnification by means of the draw tube. Accurate compara- 

 tive results may be obtained by any number of analysts provided a 

 counting chamber of definite area be used. The special counting 

 chamber recommended has a depth of 0.2 mm., the total contents of 

 the entire area being 0.2 cc. 



6. Making the Comparisons. In the identical manner as above set 

 forth (1 to 5 inclusive) prepare and examine the article to be compared 

 and of which the quality or purity is to be determined. From a com- 

 parison of the two averages of counts thus obtained, it is possible to 

 determine the approximate percentage of admixture and adulteration. 

 Let us suppose that the article in question was Cassia cinnamon and 

 the average counts were as follows. 



The standard The compared 

 cinnamon cinnamon 



Bast cells 2.5 ' 0.8 



Sclerenchyma cells 12.1 14.0 



Starch granules 50.0 13.0 



The most diagnostic tissue of cinnamon is the bast and if we use this 

 count alone (2.5 : 0.8 :: 100 per cent. : x per cent.) the conclusion 

 would be drawn that the article in question was 32 per cent, adulter- 

 ated or 32 per cent, below a good or standard quality of cassia 

 cinnamon. The other counts (sclerenchyma and starch) are corrobo- 

 rative. The bark parenchyma count is not given because the 

 microscopic appearance of this tissue is non-characteristic, the cells 

 being much broken up making counting difficult if not impossible. 

 The odor of the compared article was musty and the taste quite 

 feeble. The conclusion based upon the organolectic tests alone is that 

 the article in question is of very inferior quality made from old bark 

 and that adulteration amounts to over 30 per cent. 

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