302] Milk Analysis 179 



ation generally begins at 15 (S.G.= 1-015), an d ends at 45 



(S.G. = ro45). 



To use this instrument, pour just as much milk as will con- 

 veniently fill the lactometer cylinder into a flask and insert a 

 thermometer. Should the temperature be 6o° F., or 15 C, the 

 S.G. may at once be taken. Should the temperature, how- 

 ever, be different, it must be brought to 6o° F. by immersing 

 the flask in warm or cold water until the thermometer registers 

 the right temperature. 



Pour the milk into the cylinder, and lower the lactometer 

 carefully into the liquid. Note the graduation at the top of 

 the meniscus. 



The specific gravity of pure milk is from 30 to 34 

 of the lactometer (S.G.= 1*030 to 1*034); the addition of 

 10 per cent, of water lowers the reading to 27 to 30 , or about 

 three degrees. 



A difficulty here arises, seeing that the removal of cream 

 increases the density of milk to about 33 to 37 \ hence the lacto- 

 meter cannot be relied upon without some method of finding 

 out whether we are dealing with skim milk or whole milk. 

 This is provided in the creamometer, which usually consists 

 of an ordinary stoppered graduated cylinder of 100 c.c. 

 capacity. 



Fill the cylinder up to the 100-c.c. mark with milk, and 

 allow to stand twenty-four hours. The cream will then have 

 risen to the top, and its volume may be read off. 



Pure whole milk should give at least 10 c.c cream. 



A rough estimate of the amount of water added may be 

 obtained from using the creamometer and lactometer con- 

 jointly. 



Very many conditions, however, affect the specific gravity 

 of milk. When it is freshly drawn from the cow not only is it 

 warm, but as a rule it contains a considerable quantity of air in 



N 2 



