114 OILY FATTY ACIDS. 



contains 1 atom more of oxygen and 1 atom less of hydrogen 

 than the pure oleic acid, being represented by the formula 

 C 36 H 32 O 4 .HO. This acid yields no sebacic acid on dry distillation. 

 Hence it is that oleic acid, when not perfectly pure, that is to say, 

 when changed by the access of oxygen, often yields only very little 

 sebacic acid, while the quantities of capric and caprylic acids which 

 are developed, remain constant. 



If, however, oleic acid be exposed at a higher temperature to 

 the action of oxygen, it rapidly assumes a rancid odour, becomes 

 yellowish and more easily fusible, does not solidify so perfectly 

 when exposed to cold, and its composition is represented by the 

 formula C 34 H 33 O 5 ; hence it may be regarded as a higher stage of 

 oxidation of the radical of margaric acid than that obtained by 

 Bromeis, and noticed in page 107- 



Elaidic acid is, according to Gottlieb, perfectly isomeric with 

 pure oleic acid, and is therefore represented by the formula 

 C 36 H 33 O 3 .HO. It is produced, as we have already mentioned, from 

 oleic acid by the action of nitrous acid, without any development 

 of gas ; it crystallises from an alcoholic solution, not in needles like 

 oleic acid, but in large plates ; it fuses at 45, may be partially 

 distilled undecomposed, dissolves readily in ether and alcohol, and 

 strongly reddens litmus. On dry distillation elaidic acid yields no 

 caprylic and capric acids, in which respect it differs essentially 

 from oleic acid. In the fluid state this acid abstracts oxygen from 

 the air, although less rapidly than oleic acid, and becomes con- 

 verted, according to Gottlieb, into a higher stage of oxidation of 

 the same radical, which we may assume to exist in oleic and elaidic 

 acids, namely into (C 36 H 33 )O 8 . How the metamorphosis of oleic 

 into elaidic acid exactly takes place, or on what it depends, are 

 points on which as yet we have no certain knowledge. 



Preparation. This acid also is obtained by the saponincation 

 of vegetable and animal fats ; the oleate of potash is extracted from 

 the soap with cold absolute alcohol ; the aqueous solution of oleate 

 of potash is then precipitated with acetate of lead, and the oleate 

 of lead (free from the margarate) is taken up from the dried preci- 

 pitate by boiling ether. If the lead-salt, after the removal of the 

 ether, be decomposed with carbonate of soda, and if the resulting 

 soda-salt be decomposed with sulphuric acid, we obtain a somewhat 

 brownish oleic acid mixed with products of oxidation. In order to 

 obtain the acid in a state of perfect purity, we must, according to 

 the directions of Gottlieb, treat it with an excess of ammonia, and 

 precipitate it with chloride of barium : the baryta-salt is then to be 



