COMPOSITION OF BUTTEK. 7 



fat. They are distinguished from the first three, namely — 

 palmitic, stearic, and oleic acid, hy being more or less 

 soluble in water, and volatile without decomposition. We 

 may therefore comprise them under the term " soluble " 

 or "volatile" acids, while the others may be called the 

 " insoluble " fatty acids. 



The latter amount to about 8 7 "5 per cent, the former to 

 from 6 to 7 per cent, of the butter-fat, butyric acid being the 

 by far predominating representative of the soluble acids. 



As far as we are aware, but one analysis of butter-fat has 

 been published, which one, moreover, is very unsatisfactory, 

 and has been proved to be positively erroneous. It is by 

 Bromeis, and quoted by Fremy and Pelouze in their " Traite 

 de Chimie." 



Margarin ... ... ... ... ... 68 



Butyrolein ... ... ... ... ... 30 



Butyrin, caprin, and caproin . . . ... ... 2 



100 



The margaric acid of Bromeis has been proved by later 

 investigators to consist of stearic acid, associated with volatUe 

 acids ; and this circumstance explains why Bromeis so 

 greatly underrated the quantity of volatile acids. At the 

 same time, it has never been proved to satisfaction that there 

 is any difiference between the oleic acid of butter and that of 

 other fats. " It appears from the experiments of GottKeb, 

 that it is really identical with oleic acid, and exhibits 

 the characters observed by Bromeis only after it has been 

 considerably altered by exposure to the air." (Watts' Dic- 

 tionary.) It will be conclusively shown, in a subsequent 

 chapter, that the quantity of volatile acids is much more 

 considerable than the analysis above quoted would lead 

 one to believe. 



