966" OILY ACIDS. 



Sebacic acid, HO + C 10 H 8 O 3 . Oleic acid from both the dry- 

 ing and non -drying oils, from tallow and every other source, 

 affords among the products of its dry distillation a matter which 

 becomes concrete on cooling and is sebacic acid, easily recog- 

 nised by its solubility in water and its property of giving a 

 white precipitate with a salt of lead. This acid is prepared by 

 washing with boiling water the solid and liquid products of the 

 distillation of oleic acid or any of the fats which contain oleic 

 acid, so long as the solution gives crystals on cooling. These 

 crystals are washed with cold water, and crystallized repeatedly 

 from boiling water till they are colourless and free from empyreu- 

 matic odour. 



Sebacic acid greatly resembles benzoic acid in appearance, and 

 crystallizes in white very light plates or needles of a pearly 

 lustre ; it reddens litmus and has an acid taste, loses nothing 

 at 212, fuses at 260.6, and sublimes at a higher temperature 

 without alteration. It is but sparingly soluble in cold water, 

 but dissolves easily in boiling water and also in alcohol and 

 ether. 



Sebates. The solution of sebacic acid throws down white 

 precipitates from salts of silver and lead. The sebates of the 

 alkaline bases are very soluble. Sebacic ether has been formed 

 in the usual way, by transmitting a stream of hydrochloric acid 

 gas through an alcoholic solution of sebacic acid. 



Elaidic acid, C 72 H 66 O 5 . When a non-drying oil is mixed 

 with nitrate of suboxide of mercury or with peroxide of nitro- 

 gen, it gradually becomes solid. This change is due to the 

 transformation of the oleic acid of the oil into elaidic acid, 

 which remains in combination with oxide of glyceryl, forming 

 elaidine or the ela'idate of glyceryl, which is solid and crystalline 

 at the usual temperature. When nitrate of mercury is used in 

 this experiment a portion of the mercury is reduced. To pre- 

 pare elaidic acid, peroxide of nitrogen produced by the action 

 of nitric acid on starch is carried through oleic acid free from 

 margaric acid, in a vessel surrounded by cold water. The oleic 

 acid after a time concretes into a mass composed of considerable 

 leaflets, which is washed with boiling water, then dissolved in 

 an equal bulk of alcohol and left to crystallize. Pearly crystals 

 in tables are obtained, which are expressed between folds of 

 blotting paper and crystallized several times from alcohol 

 (Meyer). Elai'dic acid forms thin leaflets of a silvery lustre, 



