Babcock Test for other Milk Products. 91 



98. The reason why the Babcock test fails to show all 

 the fat present in skim milk must be sought in one or 

 two causes : a trace of fat may be dissolved by the sul- 

 furic acid, or owing to the minuteness of the fat glob- 

 ules of such milk they are not brought together in 

 the neck of the bottles at the speed used with the Bab- 

 cock test. The latter cause is the more likely explana- 

 tion. If a drop of the dark liquid obtained in a Bab- 

 cock bottle from a test of whole milk be placed on a 

 slide under the microscope, it will be seen that a fair 

 number of very minute fat globules are found in the 

 liquid. These globules are not brought into the column 

 of fat in the neck of the bottle by the centrifugal force 

 exerted in the Babcock test, even if the bottles are 

 whirled in a turbine tester in which they are heated 

 to 200 F. or higher (see 71) ; the loss of the fat con- 

 tained in these fine globules is compensated for, in the 

 testing of whole milk, by a liberal reading of the fat 

 column, the reading being taken from the bottom of 

 the fat to the top of the upper meniscus (see p. 35) ; 

 in some separator skim milk, on the other hand, not 

 enough fat remains to completely fill the neck, and the 

 reading must therefore be increased by at least five- 

 hundredths of one per cent. 



It follows from what has been said that tests of skim 

 milk showing no fat in the neck of the test bottles on 

 completion of the test, generally indicate inefficient 

 work of the centrifugal tester or of the operator, or of 



well as the Babcock test, give too low results with dairy by-products 

 low in fat, like skim milk, butter-milk, etc. The Gottlieb method for 

 this reason has been adopted by European chemists as a standard for 

 analysis of these products. (See 254). 



