EEUCIC ACID. 127 



oxygen rapidly from the air, turns yellow, and then 

 emits a rancid odor. Fusing potassa decomposes it 

 into palmitic and acetic acids. 



Of its salts only those of the alkalies (soaps) are 

 soluble in water ; these are, however, separated from 

 their solutions by eas.ily soluble salts. The lead salt, 

 (C 18 H 33 2 ) 2 Pb, forms the principal ingredient of ordi- 

 nary lead-plaster. 



Oleic acid combines directly with bromine, forming 

 a liquid dibromide, C 18 H 34 Br 2 2 , which, when treated 

 with alcoholic potassa, at the ordinary temperature, is 

 converted into crystalline monobromoleic acid C 18 !! 33 

 BrO 2 , difficult to prepare in a pure condition. 



By treatment with nitrous acid, oleic acid is con- 

 verted into elaidic add, which is isomeric with it. 

 This crystallizes in laminae, which fuse at 44-45, and 

 yield a crystalline dibromide with bromine ; fusing 

 point, 27. 



8. Erudc Add. 



C 22 H 42 2 = C 21 H 41 .CO.OH. 



Is contained in mustard-oil and in rape-seed oil in 

 the form of the glycerin ether. Rape-seed oil is de- 

 composed with litharge ; the resulting lead-plaster, 

 after being repeatedly extracted with ether, leaves 

 behind pure lead erucate, which, when decomposed 

 with hydrochloric acid, yields pure erucic acid. Long, 

 thin needles, insoluble in water, easily soluble in alcohol 

 and ether; fusing point, 33-34. 



Unites with bromine to form the dibromide, C 22 !! 42 

 Br 2 2 , which crystallizes in verrucose crystals, fuses 

 at 42-43, and yields monobromerudc add C 22 H 41 BrO 2 

 (fusing point, 33-34), when treated with alcoholic 

 potassa at the ordinary temperature. 



When carefully heated with dilute nitric acid to 60- 

 70, erucic acid is converted into brassidic add, which 

 is isomeric with it. This acid crystallizes in white, 

 lustrous laminae, fusing at 60, and yields a dibromide 

 (fusing point, 54) with bromine. 



