32 CREAMERY BUTTER MAKING 



It has been learned that the volume of the graduated 

 part of the neck is 2 c.c. Each section of the tester is 

 made to displace i c.c. when immersed in the liquid, 

 hence the two sections will just fill the scale if the latter 

 is correct. 



Calculating Speed of Tester. The speed at which 

 a tester must be run is dependent upon the diameter of the 

 wheel carrying the bottles. The larger this wheel the 

 fewer the revolutions it must make per minute to effect 

 a complete separation of the fat. 



In the following table by Farrington and Woll the 

 necessary speed per given diameter is calculated : 



Diameter of No. of revolutions 



wheel of zvheel 



in inches. per minute. 



10 1,074 



12 , ... 980 



14..... 909 



16 '... 848 



18 800 



20 ; 759 



22 . 724 



24 693 



General Pointers. Black fat is caused by 



1. Too strong acid. 



2. Too much acid. 



3. Too high a temperature of the acid or the milk. 



4. Not mixing soon enough. 



5. Dropping the acid through the milk. 



Foam on top of fat is caused by hard water, and can be 

 prevented by adding a few drops .of sulphuric acid to the 

 water. 



