Useful Rules and Tests 351 
(2) s=—l + .2 £s= 22 42, (4.2) 
32+ 4 = 8, .2 (4.2) = .84,8 + .84 = 8.84 = solids not fat, 
8.84 + 4.2 = 13.04 = total solids. 
L 6f.. 2 2 
@T=pt S+ ag rap+ oS 4 
32+4= 8,6 X 4.2 = 252+ 5 = 5.04, 
8 + 5.04 + .14 = 13.18 = total solids. 
Litmus TEst 
A method of determining whether a liquid is acid or alkaline. 
In acid solutions, blue litmus turns red. 
In alkaline solutions, red litmus turns blue. 
PHENOLPHTHALEIN TEST 
A method of determining whether a liquid is acid or alkaline. 
In acid solutions, if phenolphthalein is added no change in color is 
produced. 
In alkaline solutions, if phenolphthalein is added the liquid turns 
pink, 
To DETERMINE THE PERCENTAGE oF Lactic Acip IN MILK BY THE Us5 
or DEcINORMAL ALKALI, OR FARRINGTON’S ALKALINE 
TABLETS 
Each ec. ec. decinormal alkali neutralizes .009 grams lactic acid. 
Therefore, multiply the number of c. v. decinormal alkali used by .009 
and divide the product by the number of grams of milk taken. (Grams 
=c.c. X 1.032); e. g.: 20. ¢: of milk require 9 c. c. decinormal alkali 
to neutralize the acid. The per cent of acid is— 
.009 X 9 = .081 grams lactic acid.” 7 
.081 + 20.64 = .0039, or .39 %. 
Each alkaline tablet = 3.8 c. c. decinormal alkali. Each tablet 
is dissolved in 10 c. c. water. Each c. c. tablet solution = .38 u. « 
decinormal alkali. Therefore, each c. c. tablet solution will neutralize 
.009 X .88 = .0034 grams lactic acid. Therefore, multiply the number 
of c.c. of tablet solution used by .0034 and divide by the number of 
grams of milk taken (grams = c. c X 1.032); e. g.: 
20 c. v. of cream require 35 c. c. of tablet solution to neutralize the 
acid. The per cent of acid is— ; 
.0034 X 35 = .119 grams lactic acid. 
.119 + 20.64 = .0058, or .58%. 
