ON MILK AND MILK-TESTING 63 



beaker. The beaker is then placed on a steam bath 

 or in boiling water, and kept there until the ether, 

 alcohol, and gasoline are completely evaporated. 

 The remaining liquid is then poured into a milk- 

 testing bottle and the beaker is rinsed with a little 

 ether, which is also added to the test bottle. The 

 test bottle is then placed in boiling water for a few 

 minutes to evaporate the ether. After cooling the 

 contents of the test bottle to about 70° F., add 17.5 

 c. c. of sulphuric acid and complete the operation 

 as in the case of milk by the Babcock test. The 

 reading is multiplied by 18. In some cases, as in 

 dried skim milk, it is desirable to make the original 

 solution more concentrated by having 20 or more 

 grams in 100 c. c. of solution. 



" The following precautions must be observed in 

 using this method : 



" I. The milk powder solution must be made 

 uniform before sampling. 



" 2. The shaking of the mixture must be vigor- 

 ous and thorough after the addition of each of the 

 reagents used. 



" 3. The evaporation of the reagents added must 

 be complete, otherwise the final results are apt to 

 be too high. 



"4. The evaporation must not be carried so far 

 as to cause any appearance of solid particles in the 

 liquid. When this happens, the fat column con- 

 tains darkened material, which makes the results 

 uncertain. 



" This method is applicable to skim milk, whey, 

 and buttermilk, which usually do not give high 

 enough results by the Babcock method." 



