274 CHEMICAL TESTS AND ANALYSES 



PROTEIDS 



Determine nitrogen in 5 c.c. of the 40 per cent solution accord- 

 ing to the Gunning method, see "Milk," page 262, and multiply the 

 results by 6.38. 



LACTOSE 



Dilute five grams of a 40 per cent solution to about 40 c.c. and 

 add .6 c.c. of Fehling's copper solution. Nearly neutralize with 

 sodium hydroxide, make up to 100 c.c., filter through dry filter and 

 determine lactose in an aliquot as directed under "Milk Determina- 

 tion of Lactose," page 266. 



FAT 

 MODIFIED BABCOCK TEST 



Weigh eighteen grams, or measure 16.1 c.c. of the 40 per cent 

 solution into a standard Babcock milk test bottle. Add 4 c.c. of 

 commercial sulphuric acid, specific gravity 1.82 to 1.83. Shake im- 

 mediately until acid is thoroughly mixed with, the milk. Whirl in 

 Babcock tester for six minutes at full speed. The centrifuge must 

 run smoothly. Stop the tester gradually and remove the bottles 

 carefully so as not to break the layer of floating curd. Decant the 

 clear whey by slowly inclining the bottle. Now add two-thirds of 

 a 17.6 c.c. pipette full of water- After thoroughly shaking to 

 emulsify the curd and to wash it free of sucrose, add 4 c.c. sulphuric 

 acid, shake, whirl afid decant as before. Then add one 17.6 c.c. 

 pipette full of water, 17.5 c.c. of sulphuric acid and complete the 

 Babcock test in the usual way as directed under "Milk," page 269. 

 Multiply the reading by 2.5. 



This method yields very satisfactory results with sweetened 

 condensed milk containing not less than 4 to 5 per cent fat. With 

 condensed milk of a lower fat content the decanting of the clear 

 whey is difficult, since the curd in the partly skimmed product is 

 too heavy to float in the form of a firm cheese. 



THE ROESE GOTTLIEB METHOD 



As practiced in the Dairy Laboratory, Bureau of Chemistry, 

 Department of Agriculture 



"Weigh out 4 to 5 grams of the homogeneous sample of con- 

 densed milk into a Rohrig tube (Zeit. Unters Nahr. u. Genussm., 



