mabery. — constituents of petroleum. 175 



Action of Sulphuric Acid on Petroleum Distillates. 



Since the beginning of the petroleum industry, the sole method of re- 

 fining has depended on agitation with sulphuric acid ; yet, notwithstanding 

 the large quantities of material that sulphuric acid removes, as shown by 

 the immense sludge lieaps iu the vicinity of the refineries, the refiner has 

 not the slightest notion as to what the acid accomplishes beyond his 

 principal object, which is to prepare acceptable products for the market. 

 Neither has any scientific study been made of this problem, at least in 

 American petroleum, so far as revealed by published statements, but that 

 this is an interesting as well as a difficult subject appears fi-om results 

 described in several papers of this series. That ordinary concentrated 

 sulphuric acid has some effect on the density of petroleum distillates is 

 evident from numerous experiments described in this paper. But without 

 independent evidence, it cannot be determined just what constituents are 

 affected by the acid. That some of these constituents, present in small 

 quantity, are unstable and easily acted on by reagents is evident. The 

 refiner must avoid an elevation of temperature during treatment with the 

 acid, otherwise a color appears in the oil that is difficult to remove without 

 redistillation. Evidently an increase in temperature permits of trouble- 

 some chemical changes between the acid and the oil, with the formation 

 of products that remain in solution. The skilful refiner is also careful 

 to remove the acid by washing before adding caustic soda to avoid an ob- 

 jectionable color. 



In studying the action of sulphuric acid on different distillates from the 

 Russian oil, MarkownikofF and Oglobine * attributed the influence of the 

 acid mainly to its action on the unsaturated hydrocarbons and the oxygen 

 compounds. Having separated a series of unsaturated hydrocarbons 

 from Canadian petroleum, (Mabery and Quayle, unpublished results,) and 

 ascertained the presence of the same bodies in Ohio petroleum,! on account 

 of their unstable character and the ease with which they polymerize 

 alone, or more readily when in combination with sulphuric acid, it is 

 evident that one important office of the acid is the removal of these com- 

 pounds. With reference to the oxygen compounds in American petro- 

 leum, they seem to collect for the most part at least in the distillates above 

 225°. In the composition of their unpurified distillates, Markownikoff 

 and Oglobine found a considerable difference between the total percent- 

 ages of carbon and hydrogen and 100 per cent, which they assigned to 

 oxygen. In analysis of unpurified distillates described in this paper, the 



* Ann. Chim. Phys., (6.), II. 404. t Proc. Amer. Acad., XVII. 218. 



