ETHERS. 307 



It is a clear, pale yellowish liquid, of an ethereal, fruity odor, 

 an aromatic taste, and a neutral or slightly acid reaction. 

 Specific gravity 0.872. Boiling-point 96. 



Fats and fat oils. All true fats are compound ethers of the 

 triatomic alcohol glycerine, in which the three replaceable 

 hydrogen atoms of the hydroxyl are replaced by three univalent 

 radicals of the higher members of the fatty acids. For instance : 



/HO 



Glycerine = C 3 H 5 .3(HO) or C 3 H 5 HO 



\HO 



Stearic acid, = C 18 H 35 O.HO or C 18 H 35 O\Q 



Stearine or tristearine = C 3 H 5 .3(C 18 H 35 O).O 3 or C 3 H 5 ( 



\(c; 8 H 3 ;o).o 



Whilst all natural fats are glycerine in which the three hydro- 

 gen atoms are replaced, we may by artificial means introduce 

 but one or two acid radicals, thus forming: 



/(C 18 H 35 0)0 X(C 18 H 35 0)0 



Monostearine = C,H- HO Distearine = C,H, (C ia H,-0)O 



\HO \HO ' 



Fats are often termed glycerides; stearine being, for instance, 

 the glyceride of stearic acid. 



The principal fats consist of mixtures of palmitine, C 3 H 5 . 

 3(C 16 H 31 0).0 3 , stearine, C 3 H 5 3(C 18 H 35 0).0 3 , and oleine, C 3 H 5 . 

 3(C 18 H 33 0).0 3 . Stearine and palmitine are solids, oleine is a 

 liquid at ordinary temperature ; the relative quantity of the 

 three fats mentioned determines its solid or liquid condition. 

 The liquid fats, containing generally oleine as their chief con- 

 stituent, are called fatty oils or fixed oils in contradistinction to 

 volatile or essential oils. 



All fats, when in a pure state, are colorless, odorless, and 

 tasteless substances, which stain paper permanently; they are 

 insoluble in water, diificultly soluble in cold alcohol, easily 

 soluble in ether, bisulphide of carbon, benzene, etc. The taste 

 and color of fats are due to foreign substances, often produced 

 by a slight decomposition which has taken place in some of the 

 fat. All fats are lighter than water, and all solid fats fuse below 

 100; fats can be distilled without change at about 300, but are 



