118 Researches o« the Constitution of the Fatty Substances^ by 



Redtenbacher has, however, established the interesting fact, 

 that in this distillation it is only the oleic acid which pro- 

 duces, by its decomposition, the sebacic acid. Neither gly- 

 cerine, nor the stearin, nor the margaric acids yield any trace 

 of sebacic acid when distilled. Its origin must therefore de- 

 pend upon the constitution of the oleic acid. 



Oleic acid. — This acid, one of the most important of the 

 series of fatty bodies, is still but imperfectly known. Since 

 its original discovery by Chevreul it has been examined only 

 by Laurent ; but he distilled the acid he employed, and 

 as in this process it is almost totally decomposed, the re- 

 sults at which he arrived were very incorrect. 



The chemical history of oleic acid has been re-examined by 

 Varrentrapp. He has found the purest source of it to be oil 

 of sweet almonds, which contains no stearic acid, and but a 

 trace of mai'garic acid. The almond oil is to be saponified 

 by means of a solution of caustic potash, and this decom- 

 posed by dilute sulphuric acid. The impure oleic acid thus 

 obtained is to be digested at 212° for many hours with oxide 

 of lead, and then the mass produced macerated in the cold 

 with Eether. The oleate of lead dissolves readily in ajther, 

 but the margarate is insoluble therein, and by this means the 

 former is obtained completely pure. The filtered liquor is to 

 be then mixed with its own volume of water, and as much di- 

 lute muriatic acid to be added as converts the oleate into 

 chloride of lead. This deposits itself completely in the 

 water below, and the oleic acid remains dissolved in the tether. 

 When this is distilled off the oleic acid remains with the pro- 

 perties described by Chevreul. 



In the same manner the oleic acid of tallow or lard may be 

 obtained pure. 



A series of ten analyses, which agreed very well with one 

 another, gave for the oleic acid the following composition : 



44. atoms of Carbon 3363-1 77-10 



40 Hydrogen ... 499*2 11-44 



5 Oxygen 500-0 11-46 



4362-3 100-00 



The composition of oleate ofbarytes was found to be 

 44 atoms of Carbon = 3363-1 64-59 



39 Hydrogen = 486-7 9-35 



4 Oxygen = 400-0 7-68 



1 Barytes = 9569 18-38 



5206-7 100-00 



