62 QUESTIONS AND ANSWERS 



clear and colorless liquid. Fill the flask with hot 

 water, thus raising the fat into the graduated tube. 

 The percentage of fat can now be read. The sam- 

 ple is then whirled in a centrifugal machine and 

 another reading made. Multiply the reading by- 

 four." 



Why is it impossible to test sweetened condensed 

 milk by the Babcock method in the ordinary 

 way? 



Because the acid chars the cane sugar and does 

 not dissolve all of it. The blackened and undis- 

 solved sugar rises with the fat and makes it impos- 

 sible to secure a clear reading. 



How may the fat content of dried milk or milk 

 powder be determined? 



Van Slyke has had quite satisfactory results by 

 combining the Gottlieb and Babcock methods as 

 follows : 



" Dissolve lo grams of milk powder in lOO c. c. 

 of water. Take lo c. c. of this solution in a loo 

 c. c. glass cylinder. Add i c. c. of strong ammonia 

 and shake until thoroughly mixed with the solution. 

 Then add the following reagents, one after the 

 other, shaking vigorously after each addition be- 

 fore adding the next material : lo c. c. of 92 per cent 

 alcohol, 25 c. c. of washed ether, and 25 c. c. of 

 gasoline or, better, petroleum ether (boiling point 

 below 80° C). The cylinder is closed with a 

 tightly fitting, moistened cork stopper. The con- 

 tents of the cylinder, after thorough shaking, are 

 poured into a 200 c. c. beaker, the cylinder being 

 rinsed with a little gasoline, and this added to the 



