TESTING SKIM-MILK, WHEY, CHEESE, ETC. 95 



beaker. The beaker is then placed on a steam-bath 

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

 hol and gasoline are completely evaporated. The re- 

 maining liquid is then poured into a milk-testing bot- 

 tle, 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 a few minutes to evaporate 

 the ether. After cooling the contents of the test-bot- 

 tle to about 70 F., one adds 17.5 cc. of sulphuric acid 

 and completes 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 will be desira- 

 ble to make the original solution more concentrated 

 by having 20 or more grams in 100 cc. of solution. 

 The following precautions must be observed in using 

 this method: 



(1) The milk-powder solution must be made uni- 

 form before sampling. 



(2) The shaking of the mixture must be vigorous 

 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 contains dark ma- 

 terial, which makes the results uncertain. 



This method is applicable to skim-milk, whey and 

 buttermilk, which do not usually give high enough re- 

 sults by the Babcock method. 



