208 BUTTER-MAKING. 
divided by the 50, and multiplied by 100, would give the per- 
centage of the acid present. 
Farrington Test—The same principle is involved in the 
Farrington test. The alkali is put up in small tablets, already 
containing the indicator. These tablets contain a definite 
amount of alkali, and are represented as retaining their strength. 
However, they lose their strength if they are exposed to the 
atmosphere. The amount of alkali embodied in each tablet is 
such that when five of them are taken into a graduated cylin- 
der, the cylinder filled up with distilled water to the 97-c.c. 
Fic. 132.—Apparatus for the Farrington acid test. 
mark, and the tablets thoroughly dissolved in water, a solution 
is obtained, each cubic centimeter of which represents .01 of 
1%, of acid, providing 17.6 c.c. of cream is taken. The tablets 
can be made up of different strengths for the use of different- 
sized pipettes, but as the 17.6-c.c. pipette is the one which is 
used in the ordinary Babcock test, directions are given for the 
use of that pipette only. For a more detailed description of 
the acid tests see ‘‘ Milk Testing,” by Farrington and Woll. 
Amount of Acid to Develop.—The amount of acid to develop 
in cream depends upon the amount of fat present in the cream, 
and to some extent upon the market on which the butter is 
