DAIRY PRODUCTS. 41 



fluid and can then be reduced to 40 0., without danger of solidifica- 

 tion. The difference between the specific gravities expressed at 37 C. 

 and 40 0. is not of very great magnitude, 



Blyth 1 recommends the use of a picnometer of 50 to 100 grams ca- 

 pacit} 7 , with a thermometer stopper. This is filled with water at 35 C. 

 and placed in a beaker of water at 43 0. W hen the water has reached 

 a temperature of 37.7 0. the flask is removed and weighed. 



The fat whose density is to be determ ined is treated in the same 

 manner and weighed at the same temperature. 



Wigner 2 places the butter-fat in a wide tube where a bubble of the 

 specific gravity of .896 is kept below the surface by the bulb of the 

 thermometer. At a certain temperature the bubbles will slowly sink to 

 the bottom. In butters of .911 density, above which a sample may be 

 passed as pure, these beads will sink as follows : 



Specific gravity of beads 883 .8896 



Temperature 62. 7 C. 55. 5 C. 



If the beads sink at any temperature lower than these the butter 

 will need further examination. 



Estcourt 3 describes a method of taking specific gravity of fats as 

 follows : 



The bulb of a Westphal balance is suspended in a test-tube contain- 

 ing the fat, the test-tube being immersed in paraffin, in a water bath. 

 The adjustment of the weights takes place at a temperature of 92.2 0. 

 This process has been modified by Konig. 4 



In Konig's process there are several water baths which are closed 

 with the exception of a tube for carrying off the steam. In the cover 

 of each bath are four openings for the reception of four test-tubes 1 

 inches in diameter and 8 to 9 inches long. These are fastened air-tight 

 into the openings mentioned. Each tube stands one-half inch above 

 the cover of the water bath. Each piece of apparatus when in use 

 contains in one of the tubes a sample of pure butter and in the others the 

 samples under examination. 



The specific gravity is determined by small areometers G inches long 

 and with a scale marked from .845 to .870. The numbers obtained at 

 100 C. were as follows : Pure butter, .807 ; artificial butter, .859; beef 

 fat, .860 ; mutton fat, .860 ; lard, .861 ; horse fat, .861. Mixture of pure 

 butter with other fats gave numbers between .859 and .865. 



The process of Konig has been tested by the Board of Health at Berlin 

 and found relatively useful. 5 The method has also been approved by 

 Eisner; by Arnbuhl and Dietzsch; 7 and Meyer. 



1 Foods, p. 295. 



2 Ely th, op. ciL, p. 295. 

 3 Cliem. News, vol. 34, p. 254. 



4 Industriebl Jitter, 1879, p. 455. 



'"'Sell, op. cit., p. 505. 



6 Die Praxis des Nahrungsmittolcheinikers, 2d ed., p. 50. 



7 Rep. d. Ver. Anal. Chem., 1884, p. 359. 



8 Zeit. Anal. Chem., 1881, p. 376. 



