82 



Testing Milk and Its Products. 



water is added to the balance to make the total vol- 

 ume about 18 CO. The usual quantity of acid (17.5 cc.) 

 is then added, and the test completed in the ordi- 

 nary manner. The reading of the amount of fat in 

 the neck of the test bottle will not show the correct 

 per cent, of fat in the cream unless exactly 18 grams are 

 weighed out. If less than this weight was taken the 

 per cent, of fat in the cream tested is obtained by multi- 

 plying the reading by 18, and dividing the product by 

 the Aveight of cream taken. 



Example: Weight of cream tested, 5.2 grams; reading of col- 

 umn of fat ') 9.8, ^) 9.7, average 9.75; per cent, of fat in the cream 



=33.75. 



9.7.5 X]8_ 



5.2 



It is very convenient to weigh out 18 grams of cream 



(or 9 grams) so that the 

 readings may be taken di- 

 rectly from the neck of the 

 bottle. The smaller the quan- 

 tity of cream taken for a 

 sample, the greater is the 

 error introduced by inaccu- 

 rate weighings or readings. 

 The result is rendered more 

 accurate if two or three tests 

 of a sample are made, and 

 the readings averaged. 



91a. The hydrostatic bal- 

 ance is a convenient device 

 for weighing cream and 

 other dairy products to be 

 tested by the Babcock test 

 (see fifr. .'I'la).* This balance 



Fig. HSa. The Wisconsin iiy- 

 drostatic cream balance. 



Wisconsin exp. station, bull. 105. 



