41 



more than 8Y.5 per cent, of water, and which has a lower or higher 

 specific gravity than 1.029 to 1.033, must be considered as inferior 

 or adulterated ; also when it contains less than 3 per cent, of fat, 

 and when it otherwise shows considerable deviations from the 

 figures given above. 



Yet such a milk cannot be directly considered as adulterated, 

 unless the sources of the milk have been examined, and until it 

 has been clearly demonstrated that the milk produced by the cow 

 does not show the same deviations from the average, as the milk 

 offered for sale. 



Sour milk : The sale of sour milk, i. e., such which will curdle 

 on heating, should be prevented. 



It happens frequently, especially during the summer, that milk 

 curdles before the examination could be commenced. Schroeder 

 and Dietzsch have stated that a simple determination of the specific 

 gravity of the whey is sufficient to establish an adulteration by 

 water. The specific gravity of pure whey is 1.026, and a lower 

 specific gravity would indicate addition of water. It would be 

 exceedingly desirable and would greatly aid in the inspection of 

 milk, if this statement could be verified by investigations in other 

 localities. 



The following substances are used as adulterants : 



Starch and flours: Such admixtures thicken the milk; the 

 taste and flavor of flour is easily distinguished. Such milks form, 

 on standing, a pasty sediment. After boiling or curdling, the milk 

 appears thready. The addition of starch is proved either by means 

 of the microscope, or by testing the whey after flltration and con- 

 centration to one-quarter its volume, with tincture of iodine, when 

 a blue color will ensue. 



Dextrine : Milk containing dextrine has a sweetish taste ; the 

 concentrated whey with tincture of iodine, becomes light violet or 

 the color of red wine. 



Gum arable : The presence of gum arabic is determined in 

 milk by coagulation with acetic acid, filtering and concentrating 

 the serum to one-fifth its volume. Absolute alcohol precipitates 

 the gum as a white flocculent mass resembling casein (may con- 

 tain albuminates). Chevalier and Lassaigne state that this precip- 

 itate presents a streaky appearance. 



