REPORT OP THE CHEMIST. 289 



No. 4 gave 3.04 per cent, fat ; wliicli is an agreement as close as any 

 one could expect. 



Having tJius shov/n tliat tlie centrifugal metliod was capable of 

 malcing the areometric metliod applicable to almost every sample of 

 millc, 1 undertook a new series oi experiments. In all 155 samx^les 

 were subjected to treatment. 



Of the 155 samples examined only 57 gave a good separation by 

 the Soxhlet metlicxl in 30 minutes. Of the remaining U8 about half 

 did not separate at all so as to permit a reading, and the other half 

 only after several hours. Compare this with tlie centrifugal method, 

 in which only G samples out of the whole lot required over 15 min- 

 utes for separation and only 1 was abandoned as entirely inseparable, 

 and the more general application of the process is at once apparent. 



Of the 6 samj^les mentioned above 3 were from the same cow, a 

 grade short-horn, 4 years old, weight about 800 pounds, in milk since 

 July, 1885. She gave t) quarts of milk a day; was milked at 5 a. m. 

 and 5 p. m. The samples of milk sent were taken at 5 p. m. on April 

 13, 17, 23, 1886, respectively. The food received by this cow was the 

 same as for all the others (3(3) from which samples were taken for analy- 

 sis. They received at 5 a. m, 3 pounds of wheat bran and the same of 

 hominy chops, and then as much corn (maize) fodder as they could 

 eat. The bran and chops were fed dry. In pleasant weather the 

 cows were out until 3 p. m. They were then fed 10 pounds each of 

 unthrashed oats. At 5 p, m, they got a half peck of chopped tur- 

 nips and a repetition of the morning's feed of bran and chops. 



The hominy chops used showed on analysis the following compo- 

 sition : 



Per cent. 



Water , 7. 13 



Ash 2. 53 



Ether extract or fat 9. 03 



Carbohydrates 69. 33 



Crude fiber 2. 36 



Albuminoids , i 9. 63 



Two of the other samples were received April 27 and 30 from a thor- 

 oughbred Jersey, 4 years old, weight about 600 pounds, in milk since 

 July 1, 1885, giving at the time about 5 quarts daily. On the 29th 

 of April samples of milk were also treated from the same cow, but 

 after dilution the centrifugal sepa.ration, although more than usually 

 difficult, did not require so long a time as on the occasion mentioned. 



There is nothing shown by the analysis, by the breed of cow, nor by 

 the food which gives any definite idea of the cause of the peculiarity 

 in tliesp milks which does not permit a speedy separation. It cer- 

 tainly is not the quantity of fat present, for other milks having the 

 same, more or less, amounts of fat separated without difficulty. 



In all, 90 samples were compared by the usual method of separa- 

 tion and by the centrifugal. By the former method the mean per- 

 centage of fat obtained was 4.01, and by the latter 3,88. It thus ap^ 

 pears that the numbers obtained by the centrifugal method must be 

 increased by .13 in order to correspond to those of the old method. 

 This discrepancy is readily explained when it is remembered that by 

 the centrifugal motion the x^ercentage of ether left in the emulsion 

 would naturally be less than with the former process of separation. 

 The ether-fat solution thus becomes more dilute, and consequently 

 has a low-er specific gravity. When, therefore, the percentage of fat 

 in a milk determined areometrically is calculated by the tables given 



^ 19 AG— '86 



