COMPOSITION OF BUTTER. 5 



Siearic acid, C 18 H 36 2 crystallises in laminae or needles. 

 It is quite insoluble in water, but soluble in alcohol and 

 ether, and other solvents. It melts at 69*2 C., or according 

 to some at 75 C. 100 parts of stearin yield 95*73 per cent, 

 of stearic acid. 



Stearin is the chief constituent of the harder animal fats, 

 such as beef and mutton suet, but it has been found in nearly 

 every natural fat examined in which the acid sometimes 

 occurs in the free state. 



Olein, C 57 H 104 6 or C 3 H 5 (C 18 H 33 2 ) 3 . The liquid 

 portion of all hard animal and vegetable fats, and of the 

 non-drying oils, consists of tri-olein. When quite pure it is a 

 colourless liquid, without smell or taste, easily soluble in 

 alcohol and ether, but insoluble in water. Strong nitric acid 

 converts it into an isomeric solid substance, eldidin. 



Olein yields 95*70 per cent, of oleic acid. Oleic acid, 

 C 1S H 34 2 is a neutral oily liquid, without colour, smell, or 

 taste, insoluble in water, very easily dissolved by alcohol, 

 and by all proportions of ether. It crystallises from its 

 alcoholic solution in the form of white needles, which fuse at 

 14 C., and again become solid at 4 C. 



Oleic acid is a good solvent for stearic, palmitic, and other 

 acids, the mixtures having a lower melting point than that 

 calculated ; the same may be said of mixtures of the corre- 

 sponding tri-glycerides. 



Oleic acid, when heated with solid caustic alkalies, is 

 converted into palmitate and acetate with evolution of 

 hydrogen. 



Butyrin, C 15 H 26 6 or C 3 H 5 (C 4 H 7 2 ) 3 is an oily liquid 

 possessing a rancid odour and an acrid taste. It is heavier 

 than water, and insoluble in that liquid, but easily soluble 

 in alcohol or ether. 



Butyric acid, C 4 H 8 2 the most interesting constituent 



