94-0 



Journal of Agricultural Research 



Vol. VI, No. 24 



Each tube containing the butter fat under investigation in the gas 

 analysis held about 250 gm. of material, corresponding to about 200 gm. 

 of pure fat. 1 The decrease in the quantity of iodin absorbed by a tube 

 would be 1.44 gm., indicating that the fat had absorbed 0.091 gm., or 

 63.7 c. c. of oxygen. The total quantity of gas incorporated into the 

 sample for the third month, for instance, was only 27.1 c. c, containing 

 approximately but 5.28 c. c. of oxygen in all, and this is obtained from 

 the tube in undiminished quantity in the gas analysis. After one year's 

 storage the material had absorbed only 1.54 c. c. of oxygen, and even 

 after two years' storage the presence of unabsorbed oxygen could still be 

 determined. From the foregoing it will be seen that it is very improbable 

 that any oxidation of pure butter fat occurs during storage at a tempera- 

 ture of o° F. when* the fat is stored for a reasonable length of time. It 

 was decided, however, to make an additional experiment in order to be 

 more certain on this point. 



BUTTER FAT EXPOSED TO A LARGE SURFACE OF AIR 



A sample of butter fat was prepared in the same manner as was the 

 preceding material — by melting, filtering, and washing. In addition, it 

 was given a thorough agitation on the shaking machine with four succes- 

 sive changes of warm water containing 0.5 per cent of hydrochloric acid. 

 The warm butter fat so prepared was allowed to flow through the side 

 tube of the special butter tube filled with pumice fragments until it over- 

 flowed through the glass stopcock at the top. The tube was then inverted 

 and the butter fat in the tube permitted to run out. In this manner a 

 small quantity of fat, clinging to the pumice fragments, was exposed to 

 the action of a large quantity of air, a condition just the reverse of that 

 in the previous case. The tubes were then stored at 32 F., a temperature 

 considerably higher than that used in the previous cases. The results 

 are given in Table VII. 



Table VII. — Oxidation of pure butter fat exposed to the action of a large surface of air 



at 32 F. 



[Calculated to o° C and 760 mm.] 



Days, 



30 



61 



IOO 



Total gas. 



C.c. 



98.60 

 90.30 

 89. 40 



Total carbon dioxid. 



C.c. 



Per cent. 



Total oxygen. 



C.c. 



19.50 

 16.32 

 1^.08 



Per cent. 

 19.78 

 18.07 

 17.87 



Calculated 

 oxygen. 2 



C.c. 



19. 72 

 18.06 

 17.88 



1 Eight tubes of butter fat were put up for this investigation. The average weight of material in each 

 tube was 249.5 gm. The butter-fat content of each tube was approximated as follows: This butter fat was 

 prepared to represent normal butter minus the nonfatty constituents (protein, lactose, etc.). The effort 

 was made to incorporate the average quantity of water into it, and salt also was added. With 1 per cent 

 of salt and 16 per cent of water (the maximum) in the butter fat, 250 gm. of the material in the tube would 

 consist of 2.5 gm. of salt, 40 gm.of water, and 207.5 of fat ("about 200 gm."). Taking any smaller percentage 

 of water than 16 would increase the percentage of fat, which would, of course, call for a greater absorption of 

 iodin than 1 .44 gm. , expressing the taking up of a greater quantity of oxygen than 63 . 7 c. c. This would have 

 the effect of making still more pronounced the point here brought out. 



2 After deducting the figure for carbon dioxid from the total quantity of gas extracted from the tube and 

 assuming that the residual gas is pure air — that is, approximately one- fifth oxygen. 



