DISPOSING OF MILK AND CREAM 



117 



LABORATORY PROBLEMS 



XX. To Determine the Rate of In- 

 crease of Acidity at Varying 

 Temperatures 



1. Divide a lot of milk into two 

 parts. Allow one sample to sour 

 at a relatively warm temperature 

 (75 to 80 degrees F.). Keep the 

 other sample cool with well water 

 at a temperature of 50 to 55 de- 

 grees. 



2. Determine the acidity of 

 each lot at intervals of about four 

 hours; continue until the samples 

 do not increase in acidity. % 



3. Plot a curve to show the rate 

 of the increase in the acidity of the 



millr 



Fig. 32. Cream scales.* 



Graduated 

 cylinder. Burette. 

 Pig. 33. 

 The essential 

 pieces of apparatus 

 for making acidity 

 tests of milk and 

 cream. 



*In most states the law requires cream samples to be 

 weighed for testing. 



