23 



Some operators prefer to destroy the upper meniscus by 

 dropping into the bottle at this point a few drops of a 

 liquid in which the fat is not soluble. Glymol (petrolatum 

 liquidum, IT. S. P.), known commercially as white min- 

 eral oil, gives satisfactory results and may be purchased 

 at almost any drug store. If desired it 

 may be colored with alkanet root. 1 If 

 glymol is used, the fat column included 

 in the reading is from the bottom of the 

 lower meniscus to the line between the 

 fat and the glymol. If the fat column is 

 read with the upper meniscus intact, care 

 must be taken that the eye is on a level 

 with the points on the scale at which the 

 readings are made; otherwise an error 

 will be introduced. 



TESTING SKIM MILK FOR FAT. 



While in general skim milk is tested 

 with the Babcock test in the same manner 

 as whole milk, the test does not apply to 

 it with the same degree of accuracy. The 

 reason for this is perhaps as follows : The 

 fat in milk, as already shown, exists as 

 fat globules of different sizes. In the 

 process of skimming either by the cen- 

 trifugal separator or by gravity the force 

 tending to separate the fat from the other 

 milk constituents acts more strongly upon 

 the larger globules; consequently there is 

 a much larger proportion of small globules 

 in skim milk than in the whole milk. 

 In the Babcock test the fat is driven into 

 the neck of the test bottle by centrifugal force. Here 

 again the force acts more strongly upon the larger glob- 

 ules. * Some of the smaller globules never reach the neck 

 of the test bottle. This is compensated for in testing 

 whole milk by the liberal reading of the fat column that is, 



i Hunziker and Mills, loc. cit. 



FIG. 20. Show- 

 ing method 

 of reading fat 

 column in 

 cream testing. 

 Read from a 

 to c, not a to 6, 

 nor a to d. 



