640 TESTING BUTTER 



Apparatus Required. "A Babcock centrifuge. A special sep- 

 aratory funnel. A balance which is sensitive to 0.01 gram. (A tor- 

 sion balance such as is used in the moisture test will answer if it is 

 in good condition.) An accurate set of metric weights. A 10- 

 cubic centimeter graduated glass cylinder. A 100-cubic centimeter 

 glass beaker. 



Special Separatory Funnel. -"This is essentially a separatory 

 funnel with a capillary stem. The capacity of the funnel should be 

 about 75 cubic centimeters and its weight when empty should not 

 exceed 70 grams. The stopper may be dispensed with if desired. 

 It is a convenience in the final weighing, but not a necessity. 



Special Socket. "This is a double socket for holding the above 

 funnel while centrifuging, and is made of heavy sheet copper with 

 hangers of steel. Each socket will hold two funnels. The cut 

 shows the construction and dimensions. It differs in no material 

 way from the socket ordinarily used on the Babcock centrifuge, 

 except for the opening in the side. If the dimensions given fail to 

 fit the centrifuge at hand, they may be changed to suit so long as the 

 dimensions of the barrels are not altered. Care must be taken that 

 the capillary stem of the funnel does not project far enough through 

 the hole in the socket to strike against the side of the centrifuge 

 when being whirled. It is best to fit a disk of rubber gasketing to 

 the bottom of the socket. 



Sampling the Butter. <See previous directions. 



Determining the Fat. "It will be found more economical in 

 some cases if 4 or multiples of 4 determinations are made at once. 

 In this case the 2 double sockets containing the funnels will balance 

 when placed opposite in the centrifuge. If but 1 or 2 determina- 

 tions are to be made it will be necessary to balance the centrifuge 

 by putting weights in the opposite socket. First of all the weight of 

 the clean and dry separatory funnel must be ascertained, and this 

 as well as the other weighings involved must be done with care. 

 This weight once found will suffice for all determinations made 

 with that particular funnel unless by accident some of the glass 

 should be chipped off. A slight scratch made with a file can serve 

 to identify the funnels. A paper label can not be used. 



I. Weighing the Charge. "Counterpoise the small beaker on 

 the balance and carefully weigh out 20 grams of the sample mixed as 

 directed. 



