CREAM RIPENING 79 



and slowly run this from the burette into the cream, 

 shaking the beaker after each addition of alkali. With 

 the first few additions of alkali the pinkish color pro- 

 duced quickly disappears. But when the point of neu- 

 trality approaches, the color disappears very slowly and 

 the neutralizer must be added drop by drop only. The 

 moment the cream remains pink indicates that the acid 

 has all been neutralized. The number of cubic centimeters 

 of alkali added to the cream is then noted, and from this 

 the percentage of acid is calculated according to the 

 following formula : 



No. c.c. alkali X .009 

 Percent acid = No. c.c. cream >< ^^^- 



Example : What is the percentage of acidity when 

 30 c.c. of alkali are required to neutralize 50 c.c. of cream ? 



30 X .009 



5Q ■ X 100 = M%. 



From the formula it is evident that any amount of 

 cream may be used for a test. But more accurate results 

 are obtained by using 50 c.c. than less. Where this 

 amount of cream is always used the formula may be con- 

 siderably simplified. 



Thus, by dividing the numerator and denominator by 50, the 

 . / No. c.c. alkali X .009 \ 



expression I fa X 100 I becomes (No. c.c. 



alkali X .009 X 2) or (No. C.c. alkali X .018). The acidity in 

 the problem above would therefore equal 30 X .018 = M%. 



FARRINGTON S ALKALINE TABLET TEST. 



In the Farrington test the same alkali is used as in 

 Manns', but in a dry tablet form in which it is more 



