THE MICROSCOPE AS DETECTIVE 



teristic blue colour; to hide the blue shade various 

 dyes, anetto, turmeric or carrot juice are added or 

 one of the aniline dyes, products of coal tar. This 

 form of deception became so common that now the 

 public demand yellow milk and butter. Jams made 

 from inferior or over-ripe fruit are frequently 

 coloured with coal tar dyes, so also are cheap sweets. 

 Oxide of iron is added to potted meats, sauces, etc., 

 to improve their apperance. Bottled peas, which 

 if untreated would be of a yellowish-green colour, 

 are made to appear bright green by the addition 

 of the poisonous blue vitriol ; fortunately this chemi- 

 cal unites with the chlorophyll of the peas to form 

 a compound which is insoluble in the human body 

 and so no great harm is done. We may compare 

 the chlorophyll in a healthy, undoctored green pea 

 with that in a pea which has been treated with blue 

 vitriol; under the microscope we shall notice the 

 striking difference between the two. 



When we admire the beautiful crystals which go 

 to the making of a piece of lump sugar we little 

 dream that, if those crystals were pure they would 

 be yellow. The housewife, however, demands her 

 lump sugar white so ultramarine is added to mask 

 the yellow colour and give the sugar its white 

 appearance. 



Most of these impurities are difficult or impossible 

 of detection under the microscope; they are added 

 to give the food a more pleasing appearance in the 

 first place, for there are undoubtedly certain people 

 who prefer to consume food which appeals to the 



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