36 CREAMERY BUTTER MAKING 



specific gravity of 1.032. This means that a tank that 

 holds just 1,000 pounds of water would hold 1,032 pounds 

 of milk. On the lactometer scale the i.o is omitted. A 

 reading of 32, expressed in terms of specific gravity, 

 would therefore read 1.032. 



Precautions in Making a Lactometer Test. i. A 

 lactometer test should not be made until three or four 

 hours after the milk leaves the udder of the cow. The 

 reason for this is that milk, immediately after it is drawn, 

 holds mechanically mixed with it air and probably other 

 gases, which tends to give too low a reading. 



2. The sample must be thoroughly mixed. If a layer 

 of cream is allowed to form at the surface, the conse- 

 quence is that the hollow oblong bulb will float in partially 

 skimmed milk and give too high a reading. 



3. A dirty lactometer is certain to give a false reading. 

 A lactometer should be washed in luke warm (not hot) 

 water to which a little soda or other alkali has been added, 

 and then rinsed ofif with clean water and wiped. 



II. MILK SOLIDS. 



The solids of milk include everything but the water. 

 If a sample of milk be kept at the boiling temperature 

 until all the water is evaporated, the dry, solid residue 

 that remains constitutes the solids of milk. It is con- 

 venient to divide the solids into two classes, one inclu- 

 ding all the fat, the other all the solids which are not fat. 

 In referring, therefore, to the dififerent solids of milk, we 

 speak of the "fat" and the ''solids not fat" which, to- 

 gether, constitute the "total solids." The amount of each 

 of these different solids present in milk is easily seen from 

 the composition of milk. Thus, besides water, milk con- 

 tains : 



