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 quotient (34.5-r-1000=.0345; 

 .0345+1=1.0345). 



in. 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 is 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 case 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 influence 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 



