204 ILLINOIS STATE DAIRYMEN'S ASSOCIATION. 



Commercial sulphuric acid or oil of vitriol, sp. gr. 

 1.82, is the only chemical used in this process; such 

 acid can be bought for If cents per pound in carboy 

 lots, and one pound will make about 14 tests. After 

 the milk to be tested is thoroughly mixed, the glass 

 pipette is rilled with milk up to the mark. This 

 measure of milk, about a tablespoonful, is run into 

 the glass test bottle, and the graduate full of sulphuric 

 acid is next poured into the test bottle with the milk. 



By shaking the test bottle so that the two liquids 

 (milk and acid) mix, chemical action of the acid on 

 the milk begins at once, the mixture turns dark to 

 black color and becomes very warm. The milk is 

 decomposed and the butter fat separated from the other 

 constituents. 



Centrifugal motion is then used to make this sepa- 

 ration complete and to bring the butter fat into the 

 neck of the test bottle where the quantity of it can 

 be measured by the figured scale. 



The capacity of the pipette to be usei for measuring 

 out the milk has such a relation to the graduated part 

 of the test bottle, that the scale on its neck indicates 

 per cents of butter fat; so that a milk which contains 

 butter fat that fills the tube of the test bottle from 

 to 3.4 has 3.4 per cent, butter fat. A great many differ- 

 ent mechanical devices have been proposed for hold- 

 ing the test bottles and whirling them at a speed of 

 about 800 to 1000 revolutions per minute. The object 

 of all these different machines is to make complete 

 separation of the butter fat in the test bottle from the 

 hot mixture of milk and acid. 



When the bottles are in the machines, they occupy 

 a position similar to the spokes of a horizontal wheel, 

 the necks of the test bottles pointing towards the hub. 



