METHODS OF EXAMINING MILK 



237 



moved from the centrifuge, the bottle is placed in water 

 at a temperature of 135 to 140 F. (57 to 60 C.) 

 and submerged to a point above the fat column for 15 

 minutes, after which the per cent, of fat is read off from 

 the scale. The reading is taken from the bottom of the 

 lower meniscus to the bottom of the upper one. It is 

 recommended that the upper meniscus be destroyed by 

 dropping a few drops of glymol 

 (liquid petrolatum, white min- 

 eral oil) into the test bottle and 

 the reading taken from the bot- 

 tom of the lower meniscus to 

 the line between the glymol and 

 the fat. 



Gerber Test. (Fig. 36.) 

 This test is used almost exclu- 

 sively in Europe and to some ex- 

 tent in this country. The prin- 

 ciple is the same as in the Bab- 

 cock test, except that the fat is 

 not only liberated from its emul- 

 sion by sulphuric acid but is 

 also dissolved in amyl alcohol. 

 The apparatus required con- 



x A Fio. 36. Bottle and pipettes used in 



sists of a special type of bottle Gerber test. 



(G) known as an acido-butyrometer, which has a long 

 neck containing a scale graduated in tenths, each division 

 representing 0.1 per cent, of fat, and an opening in the 

 bottom which may be closed with a rubber stopper ; also 

 three pipettes: 1 of 11 c.c. capacity to measure the milk 

 (K), an acid pipette holding 10 c.c. (H), and a 1 c.c. 

 pipette for the amyl alcohol (I). The chemicals used 

 are commercial sulphuric acid of a specific gravity of 



