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had separated. Solvent clinging to the bomb was determined by adding a small, measured amount of water t o the bomb, tilting the bomb to mix solvent and water, and analyzing the wash water by refractive index measurement. Solvent remaining in the raffinate hydrocarbons (a very small quantity at 25” C.) was determined by a similar wash procedure or estimated fiom other data on the system a t 25’ C. The amount of solvent in the raffinate layers, determined in this way, T V ~ P found to be verv close to the value determined directly during the phase diagram measurements. Phase boundary data and selectivity diagram data are both shown on Figure 8. The ends of the tie lines lir very close to the phase boundary curve, SO that the lour-component system reduces essentially to a three-conipoiimt s\-bteIn Errors A hich may arise in considering a four-component system as a three-component system M cre discussed by Francis (4,6 ) . Selectivity diagrams for the systems containing water are shorvn on Figuic 9. The data are given in Tnblc IX. The mixtures oC diethylene glycol and water were more 4 e c t i v e at a given temperature than anhydrous diethylene glycol. Furthermore, u‘c of water facilitated the complete rrmov;il of l)cn7cne f i om the
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recycle solvent. 9 disadvantage of the addition of water was that a given weight of solvent dis8olved less benzene. LITERATURE CITED
(1) Caldwell, W. F.,IND. EKG.CHEM.,38, 572-5 (1946). ( 2 ) Francis, A. W., I b i d . , 36, 1096-104 (1944). ( 3 ) Francis, A. W., J . Phys. Chtm., 56, 510--13 (1952).
Francis, A. W., “Solvent Extraction of Hydrocarborw,” pp. 250-1, in “Physical Chemistry of the Hydrocarbons,” A. Farkas, ed., New York, Academic Press, 1950. ( 5 ) I~rancis,r\. W., “Ternary Systems Separating into Two Liquid Layers,” pp 1077, 1115, in “Solubilities of Inorganic and Organic Compounds,” Supplement t o 3rd ed., A . Seidell and W. I’. Linke, eds.. New York, D. Van Sostrand Co., 1952. (6) Hillenbrand, E. F., Jr., p. 34s in “Glycols.” CI. 0. Curme, ,Jr., and F. Johnston, eds.. Sew York, Reinhold Publishing Gorp., 1952. ( 7 ) Seidell, A,, “Solubilities of Organic Compounds,” Vol. 11. p. 368, New York, D. Tan Sostrand Co., 1941. (S) Stratford, R. K., and Gurd. G . M7. (to Standard Oil Development Co.), U. s. Patent 2,302,353 (Nov. I T , 1942). (9) TT’nrlrl Petioleurn, 22, N o . 12, 72-7 (1951). (4)
I ~ E C E I Yfor E Irei-iew ) Derciriher 29, 1953,
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