120 



DIRECTIONS FOR OPERATING. 



"Measure five cubic centimeters of milk to be tested 

 with milk pipette and allow to flow into bulb of bottle. In- 

 troduce an equal measure of sulphuric acid, Sp. Gr. 1.82-1.83, 

 or that commonly supplied for Babcock test. Rotate with 

 slight up and down motion to thoroughly mix acid and milk. 

 Without delay place in machine, properly balanced and whirl 

 at about 1,500 revolutions per minute (60 turns of handle) for 

 three minutes. Introduce reading tube and fill to within 

 a fraction of an inch of top with very hot water. Whirl for 

 one to two minutes. 



"The top of the column of fat should be at or a few tenths 

 below O mark on scale. In reading deduct the amount below 

 zero, if any, from the observed reading on the bottom of the 

 column of fat, which gives the percentage of fat to one-tenth 

 of one per cent. 



"The reading tube may be inserted before first whirling; 

 read "over all" as in Babcock. 



"When a number of bottles are to be tested introduce 

 milk in all; then acid, and finally mix and whirl. 



"Keep bottles and tube clean, the latter by washing in 

 alkali or soap solution after forcing water through or by swab- 

 bing with cotton. A stiff iron or copper wire makes a good 

 ram rod!" 



THE ACIDITY OF MILK. 



Again the reader is reminded of the fact that the near'er 

 we bring pasteurization (or cooling) to the time of milking 

 the better it is, and if a certain amount of acidity has devel- 

 oped the work is useless. Prof. Farrington places the limit 

 of acidity in milk to be pasteurized at 0.2 per cent (or 11 with 

 the Mann's Test). Milk will seldom taste or smell sour before 

 There is 0.3 or 0.35per cent acid. "Milk Testing," by Profs. 

 Farrington and Woll. 



It is therefore essential to use some test for the acidity, 

 but I shall only illustrate the Mann's Acid Test in Fig. 122. 



