Useful Rules and Tests. 233 
(2) S= Spat, s= 2 2 (4.2) 
32 + 4 = 8, .2 (4.2) = .84, 8 + .84 = 8.84 = solids not fat. 
8.84 + 4.2 = 13.04 = total solids. 
5 1D: 
ye Do OE ae pe BP ig 
q 5 a 5 
42 8.6 X 42 HAs bo 5d. 
8 45.04 + 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 adted no change in color 
is produced. 
In alkaline solutions, if phenolphthalein is added the liquid turns 
pink. 
To DETERMINE THE PERCENTAGE OF Lactic AcID IN MILK BY THE 
Use or DECINORMAL ALKALI, OR FARRINGTON'S ALKALINE TABLETS. 
Hach ¢c. ¢. decinormal alkali neutralizes .009 grams lactic acid. 
Therefore, multiply the number of c. ce. decinormal alkali used by 
009 and divide the product by the number of grams of milk taken. 
(Grams = ¢. ve. X 1.082); ¢. g.; 20 c. c. of milk require 9 c. c. deci- 
normal alkali to neutralize the acid. The per cent of acid is— 
.009 < 9 = .081 grams lactic acid. 
-081 + 20.64 = .0039, or .89 %. 
Each alkaline tablet = 3.8 c. c. decinormal alkali. Each tablet 
is dissolved in 10 cv. c. water. Each c. c. tablet solution = .38 
¢. ¢. decinormal alkali. Therefore, each ¢. c. tablet solution will 
neutralize .009 x .38 = .0034 grams lactic acid. Therefore, mul- 
tiply the number of c. ¢. of tablet solution used by .0034 and 
divide by the number of grams of milk taken (grams = c. ¢. x 
1.082); e. g.. 
20 ¢. c. 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%. 
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