20 DAIRY LABORATORY GUIDE 



for obtaining correct readings at varying tempera- 

 tures. Find solids not fat, and per cent of water as 

 follows : i of fat found in the milk plus } of lactometer 

 reading equals solids not fat. Total solids are ob- 

 tained by adding the solids not fat to the fat. For 

 example: Where lactometer reading is 32 and fat is 



3.5 per cent ('^ + ^) = (8.0 + .7) = 8.7; 8.7 + 



3.5 = 12.3 = total solids. For finding per cent of 

 water in milk : solids not fat of normal milk minus 

 solids not fat in watered milk, multiplied by 100 

 and divided by solids not fat of normal milk, equals 

 per cent of adulteration. For example: 



S. N. F. Normal Milk - S. N. F. Adulterated Milk 

 S. N. F. Normal Milk 



X 100 = per cent adulteration. 



EXERCISE VI 

 Testing Acidity of Milk 



The acidity of normal milk is caused by the breaking 

 down of milk sugar by bacteria and converting it 

 into lactic acid. The change is supposed to occur 

 in the following manner : 



Milk-sugar. Water. Lactic acid. 

 C12H22O11 -]- H2O = 4C3H6O3 



There are several tests for the acidity of milk. 

 Those most commonly used are as follows: 

 Mann's Acid Test. 

 Farrington's AlkaUne Test. 



