120 AGRICULTURE OF MAINE. 



ACIDITY. 



(Five out of one hundred points). 



It seems to be a well established fact among authorities that 

 acids other than lactic acid are present in newly drawn milk. 

 Any increase in the total amount of acid over that originally 

 present in milk is due to the formation of lactic acid. Accord- 

 ing to the best authorities the formation of lactic acid in milk 

 is the result of the presence and activity of bacteria. It has 

 been demonstrated that when the total acid amounts to as much 

 as .20% the lactic acid producing bacteria have usually 

 increased sufficiently to have become thoroughly established in 

 the milk, and, in such a case, and under fairly favorable con- 

 ditions, will soon render the milk sour and unmarketable. We 

 can therefore understand the desirability of knowing definitely 

 the amount or degree of acidity in the samples submitted in 

 competition. The acidity of milk or cream is usually deter- 

 mined by titration. A gWen quantity of milk or cream, say 50 

 cubic centimeters, is treated with a few drops of phenolphtelein, 

 a chemical which in an acid solution is colorless like water but 

 which in an alkaline solution is red. To the 50 c. c. of milk 

 containing this chemical is added a sufficient amount of one- 

 tenth normal alkali to neutralize the acid, when the milk or 

 cream will be changed to a light pink color. The amount of 

 alkali required to do this is carefully noted. As one cubic 

 centimeter of one-tenth normal alkali will neutralize .009 gram 

 of acid the per cent of acid is determined by multiplying the 

 number of cubic centimeters of alkali required by .009, dividing 

 the result by 50 or the number of cubic centimeters of milk or 

 cream used and then multiplying the product by 100. Hence 

 we know that one sample of milk may contain .16% acid while 

 another may contain .28%. 



PACKAGE. 



(Ten out of one hundred points). 



Since the practice of dipping milk from open cans on the 

 street is highly objectionable, and the drawing of milk through 

 a faucet from cans in the delivery wagon is an equally bad 

 practice, we find it necessary to make use of some small pack- 



