THE MICROSCOPE AS DETECTIVE 



eye, though of doubtful purity, rather than un- 

 adulterated though perfectly pure fare. When 

 added solely for the sake of appearance it matters 

 little, but the habit of making these additions is 

 frequently cultivated to hide bad material and 

 imperfections in manufacture. 



Sometimes adulterants find their way by accident 

 into our food. A good many years ago numbers of 

 people were poisoned by drinking beer, in some 

 cases with fatal results. Tests were made and the 

 beer was found to contain arsenic but how it got 

 there remained a mystery. At length the glucose, 

 a kind of sugar used in making beer and added also 

 to a good many of our foods, was found to contain 

 the substance. Now in the making of glucose, sul- 

 phuric acid is used and in this particular case the 

 impure or commercial acid had been taken. This 

 impure acid frequently contains arsenic and, in the 

 case we mention, the results of its use were 

 disastrous. 



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