162 



MILK 



follows : Water is filled into the bottle exactly to the mark. To 

 this is added from a reliable buret 1, 5 c.c., etc., of water, or the 

 amount of water may be added from accurate pipets. The mark 

 on the neck of the bottle should correspond to the amount of 

 water added. The same precautions as to the removal of moist- 

 ure in the neck and the regulation of the temperature should be 

 taken. 



In both these methods accuracy is more easily attained if the 

 fluid is colored with some dye, as this facilitates reading. 



A third method consists in measuring exactly 2 c.c. of mercury 

 or in weighing out accurately 27.18 grams into a test bottle and 



Fig. 54. Fig. 55. 



Figs. 54, 55. Styles of centrifuges for the Babcock test. (A. H. Barber 

 Creamery Supply Co.) 



closing the mouth with a cork that has been cut so as to have a 

 square end. The cork is pushed down to the 10 per cent, mark and 

 the bottle inverted. The column of mercury should exactly reach 

 the mark. 



The pipets used in the Babcock test can be tested by running 

 17.6 c.c. of water into them from an accurate buret. 



After the sulphuric acid has been thoroughly mixed with the 

 milk and the mixture has assumed a dark brown color, the bottles 

 should be weighed (Figs. 50-53), as it is important to properly bal- 

 ance the centrifuge (Figs. 54-56). The number of revolutions 

 required to give the best results depends upon the diameter of 



