356 CHEMICAL TESTS AND ANALYSES 



according to the Gunning method, see "Milk," and multiply the re- 

 sults 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 Determination of Lactose." 



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 immediately 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 float- 

 ing 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 and 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." 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 



o 



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 

 condensed milk into a Rohrig tube (Zeit. Unters. Nahr. u. Ge- 

 nussm., 1905, 9:531) or some similar apparatus and dilute with 

 water in the tube to about 10.5 c.c. or, if preferred, weigh into 



