The Lactometer and Its Application. 105 



corrections for all kinds of milk, whether rich or poor. 

 But the error introduced by the use of one table for all 

 kinds of whole milk within a comparatively small 

 range of temperature, like ten degrees above or below 

 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 taking the spe- 

 cific gravity of a sample of milk by means of a lacto- 

 meter, 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 corrections 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 32.5 

 it will be about 32.5+.4=32.9 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 aiove the lactometer scale so that the tern- 



