92 



The colloidal asphaltic matter in crude oil and the yellow colouring 

 matter in benzine, kerosene, and other distillates which is largely 

 caused by " tar-fog " mechanically carried over, may be removed 

 by coagulation (and solution) brought about by agitation with strong 

 sulphuric acid. Direct adsorption on specific surfaces however, is 

 equally effective. The writer has shown that floridin, Fuller's earth, 

 and bauxite which, when freshly ignited, possess powerful adsorptive 



action, follow the weU-known exponential adsorption rule : — 



1 



Y/m = ac". For example, using a 0-25 per cent, solution of a crude 

 asphaltic base oil in benzine as a test liquid, constant values of n were 

 obtained and the Y/m — c curves were of the usual parabolic type. 



The aj)plication of the adsorptive action of these substances in 

 the refining of various distUlates is well known and much of the 

 theoretical side has been admirably expounded by Day and his 

 co-workers (Proc. Amer. Phil. Soc, 1897, 36, No. 154; Trans. Petr. 

 Congress, Paris, 365 ; GUpin and Cram, U.S. Oeol. Survey Bull., 365 ; 

 Washington, 1908; and Gilpin and Bransky, U.S. Oeol. Survey Bull., 

 475, Washington, 1911. See also Richardson and McKenzie, Amer. 

 Jour. Sci., May 1910; Richardson and Wallace, Jour. Soc. Chem. Ind., 

 March 1912; Porter, Bull. 315 U.S. Geol. Survey, 1907). 



In brief, the following conclusions were arrived at : — 



(1) Fuller's earth tends to retain the unsaturated hydro- 

 carbons and sulphur compounds in petroleum, thus exercising 

 a selective action on the oil. 



(2) When crude petroleum diffuses upwards through a 

 column of Fuller's earth a fractionation of the oil occurs. The 

 oil displaced by water from the earth at the top of the tube 

 is lower in density than that from the bottom of the tube. 



(3) The aromatic hydrocarbon in a mixture of a paraffin 

 oil and benzene tends to collect in the lower end of the diffusion 

 column. 



Gilpin and Schnerberger {Amer. Chem. Jour., 1913, 50, 59) consider 

 that the Fuller's earth behaves as a dialysing septum which allows 

 paraffins and saturated hydrocarbons to pass freely but adsorbs 

 bitumen, aromatic hydrocarbons, sulphur, and nitrogen compounds. 

 The determining factor is surface. Similar views are propounded 

 by Gurwitsch {Petr., 1912, 8, 65) who ascribes Day's results not to 

 capillarity but to specific surface adsorption. This author shows 

 that floridin will adsorb solid paraffin from solution in petroleum 

 spirit and benzol, but not from lubricating oU. An interesting 

 observation was made by Herr {Petr., 1909, 4, 1284), who filtered 

 Baku oil through fuller's earth and discovered that all the formolite 

 forming compounds were removed, i.e., the unsaturated compounds 

 which react with formoUn were adsorbed on the mineral gel. 



It by no means follows that the compounds which are adsorbed 

 can be recovered unchanged. Being possessed almost invariably 

 of residual afl&nity the close contact afforded in the adsorbed layer . 

 promotes condensation and polymerisation, and thus Gurwitsch 



