18 DAIRY LABORATORY GUIDE 



Testing Strength of Acid 



Test strength of acid by finding its specific gravity, 

 which should be 1.82 to 1.83. This can be done by 

 weighing an exact measured volume of acid and 

 comparing its weight with the same volume of 

 distilled water. Then divide the Weight of the acid 

 by the weight of the same volume of water and the 

 quotient will be the specific gravity of the acid. If 

 the fat column is very light and contains white 

 specks the acid is too weak, not enough used, or 

 milk was too cold. If very dark or if it contains 

 black species the acid is too. strong, too much was 

 used, or milk or acid was too hot. The fat column 

 should be of a light straw color. 



EXERCISE V 



Use of the Lactometer 



The lactometer is used to determine the specific 

 gravity of a liquid; that is, its weight compared with 

 the weight of an equal volume of distilled water. 

 Where a given volume of distilled water weighs one 

 pound, an equal volume of whole milk weighs 1.029 to 

 1.033, depending upon the per cent and kind of solids 

 present. The higher the per cent of fat in milk the less 

 the specific gravity and vice versa. The specific grav- 

 ity of milk serum is 1.036. That of fat is .93. The 

 Quevenne lactometer is generally used. Examine the 

 lactometer carefully and note enclosed thermometer 

 and graduations. Place in graduated beaker of milk 



