42 ANALYSIS AND ADULTERATIONS OF BUTTER. 



the path, which led us to the above conclusions, though 

 improved methods have now superseded our original one, 

 which was certainly somewhat imperfect. 



To obtain the fat in a state of purity, free from the admix- 

 tures with which it is associated in commercial butter, in the 

 proportion, on an average of 85 parts of fat and 15 parts of 

 water, curd, and salt, it is merely necessary to fuse the butter 

 in a test tube or small beaker in a water-bath, to allow the 

 water and the solid particles to subside for the most part, 

 and then to pour the fat upon a dry filter, care being taken 

 to keep the aqueous solution in the beaker, as it would pass 

 through the filter and contaminate the fat. The paper and 

 the funnel are first to be heated in the water-bath, or better 

 still, a double funnel, one with a warm water-jacket, is used 

 to keep the fat in a state of fusion. It is also quite practi- 

 cable to put both the funnel and the small light beaker, in 

 which the bright yellow oil is collected, into the water oven, 

 whilst filtering. If done in the cold air the fat soon solidifies, 

 and filtration, of course, stops. Thus the fat is obtained in a 

 state of perfect purity and quite free from moisture ; on drying 

 in the water-bath it does not in the least diminish in weight, 

 and on incineration it leaves no trace of mineral matter. It 

 is allowed to cool, and is then in a state fit for analysis. 



All natural fats, as far as is at present known, are mixtures 

 of the tri-glycerides of different acids of the fatty and of the 

 oleic acid series ; they are ethers of the alcohol radicle 

 glyceryl, and, like all ethers, they are broken up by the 

 action of caustic potash into an alcohol, namely, glycerin, 

 and the potash salts of the various acids. Thus stearin 

 yields glycerin and stearate of potash, thus, 



3 C 18 H S5 2 , C 3 H 5 + 3 KHO = 3 C 18 H 35 K0 2 + 3 HO, C 3 H 5 , 

 and butyrin splits up into glycerin and butyrate of potash, 

 3 C 4 H 7 2 , C 3 H 5 + 3 KHO = 3 C 4 H 7 K0 2 + 3 HO, C 3 H 5 . 



