Useful Rules and Tests 351 



(2) S = -4 + .2 f, S = -4- + 2. (4.2) 



32 -r- 4 = 8, .2 (4.2) = .84, 8 + .84 = 8.84 = solids not fat. 

 8.84 + 4.2 = 13.04 = total solids. 



32 -f- 4 = 8, 6 X 4.2 = 25.2 -=- 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 ACID IN MILK BY THE USE 



OF DECINORMAL ALKALI, OR FARRINGTON'S ALKALINE 



TABLETS 



Each c. c. decinormal alkali neutralizes .009 grams lactic acid. 

 Therefore, multiply the number of c. c. 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 c. c. 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. 



.081 -r- 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 c. c. 

 decinormal alkali. Therefore, each c. c. tablet solution will neutralize 

 .009 X .38 = .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. 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 -r- 20.64 = .0058, or .58%. 



