82 ANALYSIS AND ADULTERATIONS OF BUTTER. 



are but a very few fats which are liquid at that temperature, 

 and the gravity of which can therefore be taken at that 

 point. ]STo lower point than 69*7 C., the melting point of 

 stearin, should have been adopted, and 100 C. would have 

 been far more, in accordance with the obvious wants than 

 100 F. As the test is but of very recent origin, we hope 

 that a new point may in future be adopted, for as yet it is 

 not too late to mend. 



The application of the well-known specific gravity bubbles 

 to the measurement of the specific gravity of fats was first 

 proposed by Mr. G. Wigner, F.C.S.,* who urges in favour of 

 its adoption equal accuracy with other methods, and the 

 small quantity needed, even as little as 200 grains being 

 sufficient. 



The following is the mode of procedure adopted : 



" Pour the liquid fat into a test tube of suitable size, put 

 in the bubble, cool the fat until the bubble rises, then 

 transfer the tube to a water bath, and raise the temperature 

 of the water very slowly, until the bubble begins to sink, 

 read the temperature at this time for comparison with genuine 

 butter." 



The following results obtained by Mr. Wigner were given 

 to show the bulbs likely to prove most suitable. 



" Two bubbles were selected (the specific gravity of No. 1 

 was 899-7, of No. 2, 895-7), both taken, of course, at 60 F. 

 In a sample of butter, which at 100 F. had an 'actual 

 density' of 913, No. 1 bubble sank at 131 F. ; No. 2, at 

 144 fe F. In another sample of fat, having an actual density 

 of 911-3, No. 1 bubble sank at 123 F., No. 2, at 135 F." 



Subsequently t Mr. Wigner pointed out an element of 

 error which this process evidently contained, namely, the 



* Note on the Specific Gravity of Fats. Analyst, No. 2, April, 

 1876. 

 t Analyst, No. 8, October, 1876. 



