290 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



for tlie old method of separation, it should be increased by .13 in or- 

 der to reprosont the actual quantity present. 



I think it safe to conclude, from the data which have been obtained, 

 first, that the method of iSoxhlet cannot be applied to the determina- 

 tion of fat in American milks, especially if they be from individual 

 animals. It works somewhat better on mixed milks from a large 

 dairy, but even in this case it is a rare thing to secure a prompt sep- 

 aration, and in most cases the method would be very difficult of aj)- 

 plication. 



Second. That_ by the use of the centrifugal machine described a 

 prompt separation or the ether-fat solution can be obtained in all 

 cases, even in those in which after 48 hours no separation whatever 

 takes place by the usual method. 



Third. That the estimation of the fat in milk by Soxhlet's areometer 

 can only be accurately secured when standard volumes of aqueous 

 ether and caustic potash are employed, when the volume of the ether- 

 fat solution separated is sensibly constant, and the time employed in 

 separation sensibly the same. These conditions can only be secured 

 by the use of the centrifugal machine described. 



I propose to use a centrifugal apparatus also for assisting in the 

 separation of the ether-fat solution in the lactobutyrometer; and it 

 has already proved its usefulness in separating precipitates which sub- 

 side very slowly. 



I am of the opinion that such a machine would prove of great value 

 in every chemical laboratory aside from its utility in determining the 

 fats in milk. 



The process just mentioned was first used in May, 1885, at the De- 

 partment of Agriculture, and a full description of it was given at 

 Buffalo in August, 1886, before the chemical section of the Associa- 

 tion for the Advancement of Science. 



A machine resembling this has lately been patented in Germany by 

 Laval under the name of Lactokrit. The disk of this machine is so 

 arranged as to be capable of a high rate of revolution, viz, 6,000 per 

 minute. 



The milk in which the fat is to be estimated is first treated with an 

 equal volume of a mixture of 20 parts concentrated citric acid and 1 

 part of sulphurous acid. After shaking, the test-tube containing the 

 milk mixture is warmed to 30° C, or above, and the tubes which fit 

 into the revolving disk are filled with the mixture and put in posi- 

 tion. The temperature of the tubes is kept at 50"* C by means of a 

 bath of hot water. 



In 5 minutes the fat is separated, and the percentage thereof read 

 off by the graduations on the tubes containing it. (Chem. Central- 

 hlatt, No. 42, October, 1880, pp. 797 et seq.) 



ADAMS METHOD FOR THE GRAVIMETRIC ESTIMATION OF FAT IN MILK. 



This method was first described in The Analyst, Volume 10, i:>p. 46 

 and following. Five cubic centimeters of the milk are placed on a 

 strip of blotting or filtering paper, previously exhausted witli ether, 

 and rapidly <lrio(l. The paper may be cut into strips 2 inclies wide 

 and 20 inches long. After the drying is complete the strip (^f paper 

 is rolled into a coil and extracted in a Soxhlet apparatus with ether. 

 This method has been proved by careful experiment to be very exact, 

 and ^ives a slightly higher percentage of fat than any other gravi- 

 metric method heretofore i^roposed. 



