26 Testing Milk and Its Products. 



milk thereby changed so as to render difficult a proper 

 sampling. The butter fat is not, however, changed in 

 the process of souring; this has been shown by one of us, 

 in a series of tests which were measured from one sample 

 of sweet milk into six test bottles. 



A test of the milk in one of these test bottles was made 

 every month for six months, and approximately the same 

 amount of fat was obtained in the tests throughout the 

 series, as was found originally in the milk when tested 

 in a sweet condition. 1 If the milk is in condition to be 

 sampled, its souring does not therefore interfere with its 

 being tested by the Babcock test or with the accuracy of 

 the results obtained. 



In order to facilitate the sampling of sour or loppered 

 milk, some chemical may be added which will re-dissolve 

 the coagulated casein and produce a uniform mixture that 

 can be readily measured with a pipette. Any alkali 

 (powdered potash or soda, or liquid ammonia) will pro- 

 duce this effect. Only a very small quantity of powdered 

 alkali is necessary for this purpose. The complete action 

 of the alkali on sour milk requires a little time, and the 

 operator should not try to hasten the solution by adding 

 too much alkali. An excess of alkali will often cause 

 such a violent action of the sulfuric acid on the milk to 

 which the acid is added (on account of the heat generated 

 or the presence of carbonates in the alkali) that the mix- 

 ture will be thrown out of the neck of the test bottle when 

 this is shaken in mixing the milk and the acid (37). 

 When powdered alkali is added to the milk, it should be 



1 See Hoard's Dairyman, April 8, 1892. The same holds true for cream, 

 as shown by Winton (U. S. Dept. Agr., Div. of Chemistry, bull. 43, p. 112). 



