104 Testing Milk and Its Products. 



The specific gravity is changed to lactometer degrees 

 by multiplying by 1000 and subtracting 1000 from the 

 product. 



Example: Given, the specific gravity of a sample of milk, 

 1.0345; corresponding lactometer degree, 1.0345X1000 — 1000= 

 34.5. 



Conversely, if the lactometer degree is known, the 



corresponding specific gravity is found by dividing by 



1000 and adding 1 to the quotie^t''(34.5-Hl000=.0345; 



.0345+1=1.0345). 



111. Influence of temperature. Like most liquids, 

 milk will expand on being warmed, and the same vol- 

 ume will, therefore, weigh less when warm than before; 

 that is, its specific gravity will be decreased. It follows 

 then that a lactometer is only correct for the tempera- 

 ture at which it is standardized. If a lactometer sinks 

 to the 32-mark in a sample of milk of a temperature of 

 60° F., it will only sink to, say 33, if the temperature 

 of the milk i^ 50° F., and will sink farther down, e. g., 

 to 31, if the temperature is 70° F. Lactometers are 

 generally standardized at 60° F., and to show the cor- 

 rect specific gravity the milk to be tested should first be 

 warmed (or cooled, as the ease may be) to exactly 

 60° F. 



112. Correction tables. Tables have been constructed 

 for correcting errors in lactometer readings due to 

 differences in temperature. As the fat content of a 

 sample of milk has a marked infl.uence on its specific 

 gravity at different temperatures, the co-efficient of 

 expansion of fat differing greatly from that of "the 

 milk serum, the table cannot give absolutely accurate 



