240 THE MICROSCOPE. 



Pure wheat-flour is almost entirely dissolved in a strong 

 solution of potash, containing twelve per cent, of the alkali j 

 but mineral substances used for the purpose of adultera- 

 tion remain undissolved. 



Wheat-flour is frequently adulterated with various sub- 

 stances ; and in the detection of these adulterations, the 

 microscope, together with a slight knowledge of the action 

 of chemical re-agents, lends important assistance. It 

 enables us to judge of the size, shape, and markings on the 

 starch grains, and thereby to distinguish the granules of 



Fig. 146. Wheat-Flour Starch-granules, with a small portion of its cellulose. 

 (Magnified 420 diameters.) 



one meal from that of another. In some cases the micro- 

 scopic examination is aided by an application of a solu- 

 tion of potash. Thus we may readily detect the mixture 

 of wheat-flour with either potato-starch, meal of the 

 pea or bean, by the addition of a little water to a small 

 quantity of the flour, then, by adding a few drops of 

 a solution of potash (made of the strength one part liquid 

 potash to three parts of water), the granules of the potato- 



