158 PURIFICATION OF PETROLEAN OILS. 



speedily took first an olive and then a red colour ; in fact, the result was 

 the same as in the case of the kernel itself. As I perceived that the 

 absence of sugar was the cause of the etherised extract not developing 

 the red colour on the application of sulphuric acid, I conceived the idea 

 of replacing the natural saccharine matter of the seed by common sugar. 

 Experiment encouraged that idea, for the result in all cases was the same 

 phenomenon of red colour, and therefore the presence of sugar is abso- 

 lutely necessary to produce it. After I had ascertained in what parts of 

 the kernel that red colour could by the aid of sulphuric acid be pro- 

 duced, I was desirous of assuring myself whether exterior agents had 

 any influence on the production of this phenomenon. I first tried the 

 effect of light, and for that purpose exposed one portion of the mixture 

 of the nut and acid to the rays of the sun, and kept another portion in 

 darkness. In both cases the red colour made its appearance after a short 

 time, with nearly the same degree of intensity. The nest agent experi- 

 mented upon was the atmosphere, and two quantities of the solution 

 were kept, the one in the open air, the other in an hermetically sealed 

 vase. The result was that in the latter no colour made its appearance, 

 while in the former it was very vivid. At one time I fancied that the 

 colour was attributable to the admixture of a small quantity of water, 

 but further experiments proved that water was of no service, that oxygen 

 alone of all atmospheric agents had any influence. The path of a cur- 

 rent of air passed over the mixture of oil, sulphuric acid, and saccharine, 

 could be traced by the appearance of the bright red crimson on the parts 

 of the surface exposed to its influence. The pulp divested of oil by the 

 aid of ether, contains albumen, more or less coagulated ; an albuminous 

 matter that is not coagulated by ether, although it is by alcohol and 

 heat ; tannin, precipitated by salts of iron, or carbonate of potash ; an 

 azotic matter, combined with an organic acid ; a saccharine matter, which 

 is the principal agent in producing the red colour of the oil, by the 

 addition of sulphuric acid. To dye stuffs, it is only necessary to boil 

 them in an infusion of the kernels of the seed of owala, or of the cake. 

 They are then exposed to the air, and the result is a rich brown colour, 

 and this colour can be varied by the different mordants, or of etain ; if 

 put into an iron bath, they become very black. 



The seed of owala may be considered one of those substances which 

 are richest in oil principle. Oil obtained from it can be employed for 

 domestic purposes, in mechanical industry, and in soap making. The 

 residuum, or tourtean, which remains after the extraction of the oil, is a 

 powerful dye, especially to produce black, and the remains of this tour- 

 tean used for that purpose will serve for " engrais." Lastly, we have 

 seen that there exists in the kernel a curious principle, at least in a 

 scientific point of view — viz., that of taking a crimson hue when acted 

 upon by a saccharine matter and concentrated sulphuric acid. 



