TESTING BY THE LACTOMETER 179 



ity and the scale of the Quevenne lactometer is shown 

 as follows: 



SPECIFIC Reading of 



GRAVITY Quevenne lactometer 



1.015 15 



1.020 20 



1.025 25 



1.030 30 



1.035, etc 35, etc 



Corrections for temperature. The Quevenne lac- 

 tometer is graduated to give correct results at 60 F. 

 When it is used in milk, the milk should be at 60 F., 

 or, if at some temperature above or below 60 F., a 

 correction of the lactometer reading must be made. 

 This correction can be closely made by adding to the 

 lactometer reading .1 for each degree above 60 F., 

 or by subtracting .1 for each degree below 60 F. 

 For more exact corrections, consult table on the fol- 

 lowing page. 



The Quevenne lactometer should carry a thermom- 

 eter, the scale of which is placed for convenience above 

 the lactometer scale. 



Process of using Quevenne lactometer. The sam- 

 ple of milk to be tested for specific gravity is brought 

 to a temperature between 50 and 70 F. For con- 

 venience the milk is placed in a cylinder (Fig. 49), 

 which is nearly filled. The lactometer is carefully 

 lowered into the milk until it floats and is allowed to 

 remain half a minute or more. Then one reads and 

 records (i) the point at which the lactometer scale 

 comes in contact with the upper surface of the milk; 

 and (2) the temperature. The lactometer reading is 



