The Bdbcock Test. 53 



removed before the position of the meniscus of the water 

 is noted; if a metal standard measure is used, it must be 

 kept free from rust or tarnish. 



60. Intermediate divisions. The space between and 

 10 on the scale of the Babcock test bottle is divided into 

 50 divisions, each five of which, as previously shown, 

 representing 1 per cent. (44). Since these intermediate 

 divisions are generally made with a dividing machine, 

 they are as a rule correct, but it may happen that the 

 divisions have been inaccurately placed, although the 

 space between and 10 is correct. The accuracy of the 

 intermediate divisions can be ascertained by sliding 

 along the scale a strip of paper upon which has been 

 marked the space occupied by one per cent., and com- 

 paring the space with those of each per cent, on the scale. 



61. Calibration of skim milk test bottles. The value of 

 each division on the skim milk bottles is one-twentieth 

 of one per cent. (99) and there are ten of these divisions 

 or .1 cc. in the whole scale which shows .5 per cent, 

 fat. It requires very careful work to calibrate this scale 

 and it is best done by weighing the amount of mercury 

 which will just fill the space between the first and the last 

 divisions (53) ; the correct weight of this mercury is 1.359 

 grams. 



62. Calibrating cream test bottles. The cream bottles 

 may be calibrated by any of the methods given for milk 

 bottles. A cream test bottle neck that measures thirty 

 per cent, fat will hold 6 cc., and 6 grams of water or 

 81.54 grams of mercury. 



The Trowbridge method of calibrating milk test bot- 

 tles may also be found convenient for cream bottles and 



