112 MODERN METHODS OF TESTING MILK 



easily find what per cent, of acidity is best adapted to 

 the production of the butter suiting his market, and 

 then a table like the above can be made, using .9 or 

 some other factor. 



OUTLINE STATEMENT OF SOME SPECIAL 

 PRECAUTIONS IN TESTING ACIDITY 



1. The material to be tested for acidity must be 

 thoroughly mixed before sampling for a test. 



2. The water used in preparing the alkali solution 

 and in rinsing the pipette should be neither acid nor 

 alkaline and should be soft and clean. Use distilled 

 water if possible. 



3. The alkaline tablets should be kept dry in well- 

 stoppered bottles. 



4. The alkali solution, in whatever form used, must 

 be kept from contact with the air as much as possible 

 to prevent changing strength either through evapora- 

 tion or absorption of carbon dioxide. 



5. When alkaline tablets are used, prepare a fresh 

 solution in order to be sure of its strength, if there is 

 any reason for uncertainty. 



6. The tests should be made in a good light so that 

 one can easily see the appearance of the longer-lasting 

 pink color at the end of the reaction. 



7. The appearance of the pink color at the end of 

 the test can usually be more sharply seen by diluting 

 the material examined with three or four times its vol- 

 ume of distilled water. 



