WESTPHAL BALANCE. 69 



ence of the two weights gives the weight of the water contained 

 in it. The tube is then filled with milk and immersed in water 

 at 15-55 C. (60 F.), and the milk similarly adjusted to the line ; 

 the weight of milk divided by the weight of water gives the 



15-55 

 specific gravity of the milk at TK~FFO. 



A specific gravity bottle is used in a similar manner ; the liquid, 

 after inserting the stopper and immersing the bottle in water at 

 15*55, is adjusted to the line by drawing out the excess with a 

 very fine tube. 



A Sprengel tube of 10 to 20 c.c. capacity is the most suitable 



Fig. 3, Westphal Balance. 



size ; it is a disadvantage to use a larger one, as the time taken 

 for the milk to assume the temperature of the surrounding water 

 is so much increased that there is danger of a portion of the 

 cream separating. 



The advantages of a Sprengel tube over a specific gravity 

 bottle are : 



(1) Greater surface for a given volume ; and therefore the 

 temperature is adjusted quicker. 



(2) There is no stopper to fit ; consequently, no error can be 

 due to difference of position owing to inaccuracy of fit. 



The Westphal balance (Fig. 3) consists of a balance of the 



