106 MANUAL OF GENERAL AGRICULTURE. 



and the 40 degree mark at the point to which it will sink 

 when placed in a liquid of a specific gravity of 1.040. 

 To mix thoroughly pour the sample to be tested from one 

 receptacle to another then fill a 250 c.c. or larger cylinder 

 about three fourths full. Carefully lower the lactometer 

 into the cylinder until it floats. In about half a minute 

 take the lactometer reading and the temperature read- 

 ing. In reading the lactometer degrees the mark on 

 the scale plainly visible through the upper portion of 

 the meniscus should be noted. When the lactometer de- 

 gree is known, the corresponding specific gravity is found 

 by dividing by 1000 and adding one to the quotent. 



Example: If the lactometer reading is 34.3 and the 

 temperature 60, the specific gravity is 34.3-=-1000=.0343 ; 

 .0343 plus 11.0343. 



Like most liquids milk will expand on being warmed, 

 and the same volume will weigh less when warm than 

 before ; i. e., its specific gravity will be decreased. There- 

 fore the lactometer is standardized to 60. It is incon- 

 venient to always have milk at exactly this temperature. 

 By making a temperature correction milk between 50 

 and 70 may be tested, but outside of a range of 10 on 

 either side of 60 the test will be inaccurate. To make 

 the temperature correction add .1 to the lactometer read- 

 ing for each degree above 60F., and subtract .1 for each 

 degree below 60; e.g., if the reading at 63 is 33.6 it will 

 be 33.6 plus .3=33.9 at 60. The specific gravity would 

 then be 33.9 divided by 1000=.0339. .0339 plus 

 1=1.0339. If the reading is 30 at 54 the corrected 

 reading will be 30 .6=29.4. 



Test the specific gravity of a sample of skim milk 

 and of a sample of milk with a small amount of water 

 added. 



Question: 1. Under what conditions would it be 

 difficult to detect adulteration with water? 



2. When could the presence of water be easily de- 

 tected? 



