CRBAMISRY BUTTER MAKING 85 



rotating the cup after each addition. As soon as a per- 

 manent pink color appears, the graduate is read and the 

 number of c.c. sohition used will indicate the number 

 of hundredths of one per cent of acid in the cream. Thus, 

 if it required 50 c.c. of the tablet solution to neutralize the 

 cream then the amount of acid would be .50%. From 

 this it will be seen that with the Farrington test no calcu- 

 lation of any kind is necessary. 



TESTING THE ACIDITY OF MILK. 



The acidity of milk may be determined in the same way 

 as that of cream, except that the milk need not be diluted 

 with water before adding the alkali. 



A Rapid Acid Test for Milk. Where milk is pasteur- 

 ized it is often desirable to determine approximately the 

 acidity of each lot as it arrives at the creamery. 

 It has been found that milk that contains more than .2% 

 acid cannot be satisfactorily pasteurized. Farrington and 

 Woll have devised the following rapid method for testing 

 the acidity of milk that is to be pasteurized : 



Prepare a tablet solution by adding two tablets for each 

 ounce of water. When the tablets have dissolved, take 

 the solution into the intake. Xow, as each lot is 

 dumped into the weigh can a sample of milk is taken 

 with a No. 10 brass cartridge shell and emptied into a 

 teacup. With another, or the same. No. 10 shell add a 

 measure of tablet solution to the cup. ]\Iix the alkali and 

 milk by giving the contents of the cup a rotary motion. If 

 the milk remains white it contains more than .2%- acid; 

 if it is colored, there is less than .2% acid present. 



W'here the tablet solution is prepared as above care 

 must be taken to secure equal quantities of milk and 

 solution for the test. 



