86 Testing Milk and Its Products. 



such milk they may not be brought together in the neck 

 of the bottles at the speed used with the Babcock test. 

 The latter cause is the more likely explanation. If a drop 

 of the dark liquid obtained in a Babcock bottle from a 

 test of whole .milk, be placed on a slide under the micro- 

 scope, 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 bot- 

 tle by the centrifugal force exerted in the Babcock test, 

 unless 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 contained in these fine globules is compensated 

 for, in the testing of whole milk, by a liberal reading of 

 the column of fat separated out, the reading being taken 

 from the lower meniscus of the fat to the top of the upper 

 one (see p. 35) ; in some separator skim milk, on the other 

 hand, not enough fat remains to completely fill the neck, 

 and the apparent result of the reading must therefore be 

 increased by from five-hundredths to one-tenth of one 

 per cent, or the sample tested in a double-necked skim 

 milk bottle. 



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 both. 

 The test should be repeated in such cases, using more 

 acid and whirling for full four minutes. 



In order to bring as much fat as possible into the neck 

 of the bottles in testing skim milk, it is advisable to add 

 somewhat more acid than when whole milk is tested, viz., 

 about 20 cc., and to whirl the bottles at full speed for four 



