256 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
If the reaction is alkaline, i.e., if the milk or cream 
becomes permanently pink when the phenolphthalein 
solution is added, or if the pink color appears and remains 
before the addition of the quantity of tenth-normal 
sodium hydroxide solution required for normal milk, then 
the rosolic acid test for alkalies should be applied (see 
page 260). 
Acidity Test With Babcock Pipette—The test for 
acidity may also be made by using a Babcock fat-test 
pipette to measure the milk or cream. 17.6 c.c. of milk 
or cream is placed in the cup or beaker, a few drops of 
the phenolphthalein solution added and the tenth-normal 
solution of sodium hydroxide run in slowly until the pink 
color appears and remains permanently. The per cent. 
of acid may be determined by dividing the number of c.c. 
of tenth-normal sodium hydroxide solution used by two, 
and expressing the quotient in tenths, thus: 
6 + 2 = 3, or 0.3 per cent. acid. 
Farrington’s Alkaline Tablet Test—The special 
feature of this test is the use of tablets of sodium car- 
bonate for making the alkaline solution. Each tablet 
contains sufficient alkali to neutralize 0.034 gramme of 
acid. Five tablets are placed in a 100 c.c. graduated 
cylinder and clean, soft water, preferably distilled, is 
added up to the 97 c.c. mark. The cylinder is then 
closed tightly with a stopper and laid on its side for sev- 
eral hours to give the tablets an opportunity to dissolve. 
Solution is never entirely complete, a slight flocculent 
residue remaining. After thoroughly mixing by shaking, 
17.6 c.c. of the milk or cream to be tested is measured 
into the beaker or cup with a Babcock fat-test pipette. 
The pipette is then filled with water to the 17.6 mark 
