MILK AND MILK PRODUCTS 



15 



Werner-Schmid Method. — This is suitable for sour milk and 

 for sweetened condensed milk. 10 c.c. of the milk are meas- 

 ured into a long test-tube of 50 c.c. capacity, and 10 c.c. of 

 strong hydrochloric acid added, or the milk may be weighed 

 in a small beaker and washed into the tube with the acid. 

 After mixing, the liquid is boiled i^ minutes, or the tube may 

 be corked and heated in the water-bath from 5 to 10 minutes, 

 until the liquid turns dark brown. It must not be allowed to 

 turn black. The tube and contents are 

 cooled in water, 30 c.c. of well-washed 

 ether added, shaken, and allowed to 

 stand until the line of acid and ether 

 is distinct. The cork is taken out, and 

 a double-tube arrangement, like that of 

 the ordinary wash-bottle, inserted. The 

 stopper of this should be of cork and 

 not of rubber, since it is difficult to slide 

 the glass tube in rubber, and there is a 

 possibility, also, of the ether acting on 

 the rubber and dissolving it. The lower 

 end of the exit-tube is adjusted so as to 

 rest immediately above the junction of 

 the two liquids. The ethereal solution 

 of the fat is then blown out and received 

 in a weighed flask. Two more portions 

 of ether, 10 c.c. each, are shaken with the acid liquid, blown 

 out, and added to the first. The ether is then distilled off and 

 the fat dried and weighed as above. 



Centrifugal Methods. — Among the processes for the rapid 

 determination of fat, those employing centrifugal action have 

 been found most convenient. The following method, devised 

 by Leffmann & Beam in i88g, has proved satisfactory on 

 the score of accuracy, simplicity, and ease of manipulation. 

 This process, which antedates in its successful operation 



Fig. li 



