THE BABCOCK TEST 



35 



176 c.c 



\/ 



per cent. Why do these divisions represent 

 exact percentages by weight of fat in milk, 

 when no weighing is done in testing milk? 

 We use, in testing, 17.5 cc. of milk, which 

 is known to weigh almost exactly 18 grams. 

 The graduated portion of the neck of the 

 test-bottle is made to hold exactly 2 cc. be- 

 tween the o and 10 marks. Since i cc. of 

 pure milk-fat is known to weigh .9 gram, 

 2 cc. of milk- fat, the amount required to 

 fill the neck between the o and 10 marks, 

 weighs 1.8 (.9x2) grams, which amount is 

 just 10 per cent, of the 18 grams of milk 

 sample used in testing. 



The divisions on the neck of the test-bot- 

 tle should be accurate and uniform ; the lines 

 should run straight across the neck and not 

 obliquely. When the marks and numbers 

 become indistinct from use, they can be 

 rendered clear by rubbing the scale over 

 with the lead of a pencil or with a cloth 

 having on it a little printer's ink or black 

 paint. When in use, each bottle should be 

 numbered or labeled in a distinctive way. 



FIG. 8 



PIPETTE 



MILK-MEASURING PIPETTE 



The form of pipette in common use is 

 shown in Fig. 8. Other forms are shown 

 in Figs. 9 and 10. The pipette should hold 

 17.6 cc. when filled to the mark. Since 

 about .1 cc. of milk will adhere to the in- 



