282 REPORT OP THE COMMISSIONER OF AGRICULTURE. 



a sphere. Tlie rate of the rise of temperature during the last degree 

 should not be greater than two or three tenths of a degree a minute. 



By this method agreeing duplicate or triplicate determinations can 

 be made and the melting point of fats be determined with far greater 

 accuracy than by any method heretofore proposed. 



Pure butter fat is found by this method to have a melting point of 

 about 3o°.oC. 



CHEMICAL ANALYSIS. 



Of the chemical methods employed there are only three which have 

 been found reliable by long experience. The tir.st of these consists 

 in the separation and determination of the insoluble acids of the but- 

 ter or fat under examination. It is generally known as the method 

 of Hehner and Angell, but has undergone many modifications in the 

 hands of different analysts. 



The following is a description of this method as practiced in this 

 laboratory: 



HEHNER AND ANGELL'S METHOD^ MODIFIED. 



About 4 to 5 grams of filtered fat are weighed into a patent rubber 

 stoppered bottle, by means of a pipette and weighing bottle, and 50 

 cubic centimeters of an approximately semi-normal alcoholic potash 

 solution added. Duplicate blanks, t". e., alcoholic potash withouc any 

 fat, are also measured out and all placed in the water-bath. When 

 saponification is complete they are taken off, cooled down, and the con- 

 tents run into large Erlenmeyer flasks of 300 to 400 cubic centimeters 

 capacity, the liquid adhering to tne bottle being rinsed into the flask 

 with small successive portions of boiling water. The flasks are placed 

 on the steam-bath and the alcohol evaporated. Then the amount of 

 semi-normal acid required to set free tlie fatty acids is ascertained by 

 titrating the blanks. Afterwards about 1 cubic centimeter more 

 than this amount of acid is run into the flask containing the sample, 

 which is fitted with a cork furnished with a glass tube about 1 meter 

 long. It is then heated on the bath until the fatty acids form a clear 

 stratum on the surface of the liquid, when it is removed, cooled with 

 ice water as rapidly as is consistent with the safety of the flask, the 

 tube rinsed out, and the contents carefully poured off from the cake 

 of solidified acid through a dry filter into a liter flask. After being 

 rinsed with a little cold water, about 20 cubic centimeters of boiling 

 water is poured in on the cake, the cork and tube replaced, the con- 

 tents thoroughly agitated with a circular movement, so as not to get 

 any of the contents on the cork, and the flask again placed on the 

 bath. When heated to the full temperature of the bath it is taken 

 off again, shaken well, and cooled and filtered as before. This wash- 

 ing is repeated three times, using in all about GOO to 700 cubic centi- 

 meters of water, when the filtrate is made up to 1 liter, an aliquot 

 part taken and titrated with deci-normal soda. The excess of semi- 

 normal acid used in separating the fatty acids is deducted, and the 

 remainder calculated as butyric acid. 



The flask containing the insoluble acids is carefully inverted on a 

 stand, and allowed to dry for twenty -four hours in the air, together 

 with the filter paper, the funnel-shaped neck of the Erlenmeyer flask 

 preventing the cake of acid from dropping out. The paper and flask 

 being quite dry, so that the acid does not stick to them, the cake in 



