LACTOCRITE METHOD. 25 



cup in which a perforated stopper fits tightly. The 

 stopper holds the graduated glass tube. As the fat in 

 the milk after boiling with acid has a great tendency 

 to rise, the test-glass must be well shaken before its 

 contents are poured into the cup, and when this is filled 

 the stopper must be immediately pressed down in it 

 whereby any excess of the mixture will escape through 

 the glass tube, and the test-box is filled completely. 

 After the test-boxes have been charged in this way, they 

 are ready to be placed in the disc which will hold 

 twelve at a time. The disc, which before use must be 

 heated to about 110 F. by being placed in water of 

 this temperature,has twelve cylindrical holes bored from 

 a cavity on the top, radiating and a little sloping, In 

 these the test-boxes are placed (if less than twelve test- 

 boxes are used there should always be an even number 

 placed so as not to disturb the equilibrium) and the 

 cavity is filled with water, which will keep the liquid in 

 the test-boxes from being pressed out by the centrifu- 

 gal force. The disc, which fits any stand of a Laval 

 separator, is now made to revolve for three or four 

 minutes at ordinary speed (6000 revolutions in the 

 minute). When it is again at rest, the test-boxes are 

 drawn out and the column of fat on the graduated tube 

 is read off, the divisions indicating immediately tenths 

 per cent, of butter-fat by weight." 



The results obtained with whole milks are very sat- 

 isfactory, being within one-tenth per cent, and less, of 

 those furnished by the Adams' process. With milks 

 poor in fat, however, the results are low and it fails to 



c 



