94 GUIDE TO DAIRYING IN SOUTH AFRICA 



however is not entirely reliable, because some cows' 

 milk throws up the cream better than others accord- 

 ing to the breed. But this instrument can give some 

 idea of what amount of cream one ought to get from 

 100 Ibs. of the same milk put through a separator. 



The Lactometer. 



The Lactometer is an instrument for determining 

 the weight or specific gravity of milk. It consists 

 of a glass stem with a bulb at the bottom which 

 contains either mercury or small shot. This is to 

 enable it to stand upright in a liquid. The stem is 

 graduated, generally ranging from o to 40 ; the 

 point to which the stem sinks in pure water being o, 

 while 40 would be the point to which it sinks in a 

 liquid whose specific gravity is 1040, the standard 

 of water being taken as 1000. Milk is heavier 

 than water, while separated milk is heavier than 

 whole milk and the fat is lighter than water. 



Water specific gravity = 1000 



Milk 1030 



Separator milk = above 1034 



Milk fat = 910 



A low specific gravity according to the lacto- 

 meter indicates either that the milk is very rich in 

 fat or that the milk has been watered. A high 

 specific gravity indicates that the fat has been 

 skimmed off the milk or that separator milk has 

 been added to it. 



When taking the specific gravity of milk by 

 lactometer the temperature of the milk should be 



