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Upgrading of coal derived liquid can be accomplished by super-critical solvent separation. An experimental method and an X-ray measuring technique were developed to observe the separation of coal liquid contacted with supercritical solvent. The cell is operated at constant volume and varying temperature with meaurements of pressure and X-ray photographs of the cell contents. The pressure - temperature conditions are dependent upon the total initial charge at different solvent to coal liquid ratios. The coal liquids are the bottoms of the vacuum still at the Wilsonville Solvent Refined Coal plant. Three supercritical solvents (heptane, toluene and pyridine) have been contacted with the coal liquids. The systems toluene - asphaltene and toluene - preasphaltene have also been studied. The asphaltene and preasphaltene were isolated from the W. SRC material by soxhlet extraction. An X-ray measuring technique permitted recording of the contents of the cell at each temperature - pressure condition. A laser densitometer was used to measure the optical density of the X-ray fukns. The technique for X-ray film interpretation was developed with pure toluene experiments. A calculational procedure was developed to calculate the density of the phases at different temperature - pressure conditions. Qualitative observation of the X-ray pictures indicated that toluene had intermediate solvency abilities whereas heptane and pyridine experiments confirmed the extremes in solvency power on the W. SRC material. The toluene-coal liquid experiments at ratios of 4, 3 and 2 parts of toluene per part of coal liquid yielded much information. Maximum solubility and rejection phenomena were observed in the toluene experiments. The temperatures at the maximum solubility of coal liquid in toluene were found to decrease from 300(DEGREES)C to 280(DEGREES)C as the ratio decreased from 4 to 2. Rejection of dissolved coal liquid from the solvent was also observed and interpreted with respect to the variables, pressure, temperature and ratio. The formation of a second phase was observed at 360(DEGREES)C and pressures less than 6000 kPa. The maximum solubility was found to be pressure insensitive at a ratio of 3 parts of toluene per part of coal liquid. At a ratio of 4 the maximum solubility was more pressure sensitive. The very weak influence of the pressure on the maximum solubility of asphaltene in toluene confirmed the coal liquid - toluene experiments at a ratio of 2. Supercritical toluene did not dissolve any preasphaltene.