102 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 on the 

 market at present are generally standardized at 60 F., 

 and to show the correct specific gravity the milk to be 

 tested should first be warmed (or cooled, as the case 

 may be) to exactly 60 F. As this is a somewhat slow 

 process, tables have been constructed for correcting the 

 results for errors due to differences in temperature (see 

 Appendix, Table V). 



112. 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 differ- 

 ing greatly from that of the milk serum, the table can- 



