288 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



has shown, were entirely unsuccessful. Even if the different kinds 

 of milk would permit a prompt separation by varying the quantities 

 of alkali employed, the amount for each sample could only be deter- 

 mined by numerous and todions experiments. 



I therefore turned my attention in anotlier direction. It seemed to 

 me that a centrifugal machine might bo used to secure this sei:)ara- 

 tion, and accordingly I had a cast-away drug-mill, formerly used in 

 the laboratory, modified so as to serve for this purpose. The machine 

 was so arranged as to hold four sei)aratory flasks and impart to them 

 a high speed of rotation. 



At this point ot my investigations this apparatus was finished, and 

 I immediately subjected it to a trial. 



Four samples, Avliich had not separated at all at the end of 3 hours, 

 were placed in the apparatus and whirled for 10 minutes. At the end 

 of this time 3 of them had completely separated and the fourth 

 nearly so. The apparatus was set in motion again for 5 minutes, at 

 the end of which time the separation of the fourth sample was ac- 

 complished. 



The number of revolutions per minute of the machine was about 

 250. 



It will be seen from the above that the very first trial of the ma- 

 chine was completely successful, securing a perfect separation of the 

 ether-fat solution in a few moments in samples which previous trial 

 by the usual method had failed to separate in several hours. 



The next determinations were made on a sample of milk purchased 

 at the Department restaurant. 



Duplicate flasks were treated in the usual way to secure the separa- 

 tion, and only at the end of 2-|- hours was enough clear solution ob- 

 tained to get a reading: No. 1 gave 2.40 per cent, fat; No. 2 gave 2.30 

 per cent. fat. 



The first set of samples of the same milk sepa-rated by the centrif- 

 ugal gave the percentages below : No. 1 gave 2.52 per cent.; No. 2 

 gave 2.32 per cent. fat. 



The separation took place perfectly in 10 minutes with a rate of 

 revolution of about 300 per minute. 



The second set of 4 samples was treated in the same way and 

 separated completely in 8 minutes. The following readings were ob- 

 tained: No. 1 gave 2.36 per cent, fat; No. 2 gave 2.34 per cent, fat; 

 No, 3 gave 2.31 per cent, fat; No. 4 gave 2.30 per cent. fat. 



The third set of samples separated by the centrifugal showed the 

 following x^ercentages : No. 1 gave 2.23 per cent, fat; No. 2 gave 2.30 

 per cent. fat. 



The volume of the clear ether-fat solution in each case was about 

 40 cubic centimeters. 



The next trial was with milk also purchased in the Department 

 restaurant. It proved to be one of the rare cases in which a reason- 

 ably prompt separation was secured by the old method. After 30 

 minutes about 25 cubic centimeters of the ether solution had sepa- 

 rated, which was enough to get a reading. Duplicate determinations 

 were made : No. 1 gave 2.08 per cent, fat; No, 2 gave 2.04 per cent, 

 fat. 



Four separations of the same milk were also made with the cen- 

 trifugal. Separation took place promptly in 8 minutes at a speed 

 of about 300 revolutions per minute, and tlie volume of ether fat in 

 each case was about 40 cubic centimeters : No. 1 gave 2,01 per cent. 

 fat} No. 2 gave 2.01 per cent, fat; No. 3 gave 2. 00 per cent, fat; No. 



