112 Testing Milk and Its Products. 



c. c. alkali X.009 



Per cent, acidity j x 100 



c. c. sample tested 



If 50 cc. of cream required 32 cc. of alkali solution to 

 produce a permanent pink color, the per cent, of acid in 



32 X 009 



the cream would be ^ X 100 =.58 per cent. Apart 

 50 



of this calculation may be saved by using a factor for 

 multiplying the number of cc. of alkali added in each 

 test. This factor is obtained by dividing .009 (the num- 

 ber of grams of lactic acid neutralized by one cc. of alkali 

 solution) by the number of cc. of sample tested, and mul- 

 tiplying the quotient by 100. If a 50 cc. pipette is used 

 for measuring the sample to be tested, the factor will be 

 (.009-^-50)XlOO = .018; if a 25 cc. pipette is used, the 

 factor will be (.009-5-25) X 100^.036; and if a 20 cc. 

 pipette is used, (.009^-20) Xl00 = . 045 will be the factor 

 to be applied in calculating the per cent, of acidity, the 

 number of cc. of alkali used being in all cases multiplied 

 by the particular factor corresponding to the volume of 

 the sample tested. 



130. If a Babcock milk-test pipette is taken for meas- 

 uring the milk or cream to be tested for acidity, the 

 factor will be (.009-^-17.6) X 100 =.051. This is so 

 nearly .05 that sufficiently accurate results may be 

 obtained by simply dividing the number of cc. used by 

 two; the result will be the per cent, of acid in the sample 

 tested, e. g., if 17.6 cc. of cream required 12 cc. of one- 

 tenth normal alkali to give the pink color, then the per 

 cent, of acid is 12 -=-2 = .6 per cent. 



131. Manns' testing outfit. The apparatus (see Fig. 

 40) and chemicals needed for testing the acidity of milk 



