The Lactometer and Its Application. 103 



not give absolutely accurate corrections for all kinds of 

 milk, whether rich or poor. But the error introduced 

 by the use of one table for any kind of whole milk 

 within a comparatively small range of temperature, like 

 ten degrees above or belcw 60, is too small to have any 

 importance outside of exact scientific work, and in such, 

 the specific gravity is always determined by means of a 

 picnometer or a specific-gravity bottle (248), at the exact 

 temperature at which this has been calibrated. In tak- 

 ing the specific gravity of a sample of milk by means 

 of a lactometer, the milk is always warmed or cooled 

 so that its temperature does not vary ten degrees either 

 way from 60 F. 



113. The temperature correction table for whole milk, 

 given in the Appendix shows that if, e. g., the specific 

 gravity of a sample of milk taken at 68 F. was found 

 to be 1.034, its specific gravity would be 1.0352 if the 

 milk was cooled down to 60. If the specific gravity 

 given was found at a temperature of 51, the corrected 

 specific gravity of the milk would be 1.0329. 



In practical work in factories or at the farm, suffi- 

 ciently accurate temperature correcticns may generally 

 be made by adding .1 to the lactometer reading for 

 each degree above 60 F., and subtracting .1 for each 

 degree below 60 ; e. g., if the reading at 64 is 29.5. 

 it will be about 29.5+.4=29.9 at 60 F. ; and 34.0 at 

 52 F. will be about 34.0 .8=33.2 at 60 F. The table 

 in the Appendix gives 33.0 as the corrected figure in 

 both cases. 



The scale of the thermometer in the .lactometer should 

 be placed above the lactometer scale so that the tern- 



