92 PROFITABLE DAIRYING 



LABORATORY PROBLEMS 

 XV. To Deteeminb the Acidity of Milk 



Prepare a standard tablet solution by dissolving 5 

 Farrington alkali tablets in 97 c.c. of clean, soft water. 

 The water may be condensed steam or pure rain water. 

 The tablets can be purchased in boxes containing 1,000 

 each from any dairy supply house. If kept dry and 

 away from the air, they will not lose strength. The 

 solution as prepared above is so standardized that one 

 cubic centimeter will neutralize one one-hundredths 

 per cent acidity if a 17.6 c.c. of milk is used as a sample. 

 The solution should be prepared several hours in 

 advance to allow the tablets to dissolve. The small 

 residue which does not dissolve is inert matter and 

 does not interfere with the test. After the tablets 

 have been dissolved the solution will not lose its 

 strength for several weeks. It is well, however, not to 

 mix up too much at a time and to keep the bottle well 

 corked. No indicator is necessary, because an indi- 

 cator has been incorporated in the tablets. For prac- 

 tical purposes a 100 c.c. graduated cylinder, a 17.6 c.c. 

 pipette and a white china cup comprise the apparatus 

 necessary to determine the acidity of milk and cream. 



Determine the acidity of milk, cream, etc., by the 

 following method : 



1. Using a 17.6 c.c. pipette, transfer a pipetteful of 

 the sample to be tested for acidity to a white china cup. 



2. From a graduated cylinder add sufficient tablet 

 solution to color the mixture a faintly permanent pink. 

 It is well to give the cup a rotary motion while adding 

 the solution. Some prefer to use a glass stirring rod 

 to mix the solution with the sample. 



