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The distribution of nitrogen, sulphur, metals, saturates, and aromatics, among the various molecules and particles in petroleum, is of importance in geochemical speculations on the origin of crude oil. Investigations with the ultracentrifuge are believed to give a truer picture of this distribution, while previous studies have used distillation and precipitation that alter the property being studied. Centrifugation of whole crude oil in a preparative ultracentrifuge at about 80,000 times gravity for 2-5 days gives a gradient in concentration of some constituents in the liquid and a relatively small amount of solid sediment. Examination of the solid by x-ray diffraction permitted identification of kaolinite and sodium chloride among the inorganic constituents and high-mole ular-weight waxes among the organic. Most of the asphaltenes remain in the liquid phase and are concentrated in the lower portions of the tube along with nitrogen, sulphur, nickel, and vanadium. Layer analysis of the centrifuged samples leads to a particle diameter distribution curve with a maximum at about 60 Angstroms. Viscosity is considerably affected by asphaltene content and can be used as a measure of separation.
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