The Babcock Test. 45 



frame is reversed and placed in the position shown in II. 



One or two rinsings in boiling hot water is usually 

 sufficient to effectually clean the bottles, but when they 

 have been allowed to get greasy they can be dipped into 

 a pail of hot dilute lye; this will saponify the grease 

 and after one or two rinsings in clean hot water the 

 bottles will be bright and clean. 



The black stains that sometimes stick to the inside of 

 test bottles after prolonged use, can be removed with a 

 little muriatic acid, or by means of a small stiff brush. 



48. Pipette. The difference in the weights of various 

 samples of normal milk generally falls within compara- 

 tively narrow limits ; if a given volume of water weighs 

 one pound, the same volume of the usual grades of nor- 

 mal milk will weigh from 1.029 to 1.033 pounds, or on 

 the average, 1.03 Ibs. 18 grams of water measures 18 

 cc. 1 ; 18 grams of milk will therefore take up a smaller 

 volume than 18 cc., \iz., 18 divided by 1.03, which is 

 very nearly 17.5. This is the quantity of milk taken 

 in the Babcock test. A certain amount of 

 milk will adhere to the walls of the pi- 

 pette when it is emptied, and this thin film 

 has been found to weigh about one-tenth 

 of a gram; consequently 17.6 cc. has been 

 adopted as the capacity of the pipette used 

 for delivering 18 grams of milk. 



For convenience in measuring the milk, 



' FIG. 17. Pipette 



the shape of the pipette is of importance. . points 



A, proper con- 



The mark on the stem should be two inches 



or more from the upper end of the pip- construction. 



1< Cubic centimeterr (abbreviated : cc.) are the standard used for 

 measuring volume in the metric system, similar to the quart or pint 



