Determination of Lactic Acid 205 
for the same purpose, known as Farrington’s alkaline 
tablets. Hach tablet contains an amount of alkali 
equal to 38.8 cubic centimeters of decinormal alkali, 
and a sufficient amount of phenolphthalein indicator. 
The cream to be tested is measured, and to it is 
added a solution of the tablets (one tablet in ten 
cubic centimeters of water) until the cream retains a 
pinkish tinge. The tablet solution should always 
be fresh, not more than ten hours old. The tab- 
lets themselves will keep indefinitely. The proper 
degree of acidity is indictated when 30-35 ec. c. of 
Farrington tablet solution, or 11-18 e¢.c. of deci- 
normal alkali, are required to neutralize the acid in 
20 cubic centimeters of cream. 
Determination of lactic acid in milk or cream.—Far- 
rington’s alkaline tablets may also be conveniently 
used to determine the percentage of lactic acid in any 
given sample of milk or cream. In order to do this, 
‘it is only necessary to understand that equal volumes 
of normal or decinormal acids and alkalies neutral- 
ize each other; and further, that a normal solu- 
tion of lactic acid contains 90 grams of acid in each 
liter, or 1,000 c. e. <A decinormal solution would 
contain 1-10 as much, or 9 grams in each liter, 
and a cubic centimeter would contain t000 as much 
as a liter, or .009 grams of lactic acid. Hach 
tablet of the Farrington alkali is equal in strength 
to 3.8 ec. ¢. of decinormal alkali, and if the tablet 
solution is made by dissolving 10 tablets in 100 ¢. e. 
of water, each cubic centimeter of the solution will 
be equal to .88 c¢. c. of decinormal alkali, and will 
