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Experimental results are reported for the fluid phase equilibria of the ternary system H2O—C2H6—NaCl, H2O—n‐hexane—NaCl and CH3OH—CH4—NaBr. Measurements were extended to 800 K and 250 MPa and to 450 K and 200 MPa with the methanol system. A “synthetic” method, described earlier, was used with a high pressure autoclave with improved sapphire window arrangement. Pressure‐temperature curves on the three‐dimensional pTx‐phase boundary surfaces at constant compositions, x, were obtained (“isopleths”). Temperatures, pressures and molar densities along 14, 5 and 7 isopleths for the systems with ethane, n‐hexane and methanol‐methane, respectively, are reported. Salt concentrations between 0.1 and 8 weight percent, relative to water or methanol, are applied. The addition of salt shifts the fluid‐fluid two‐phase region to higher temperatures and pressures in all three systems. The isobaric and isothermal shifts in certain regions can reach 100 K and more and 500 bar and more with 8 weight percent of salt. Even with only 0.1 weight percent 15 K shifts are observed near the respective critical curves. For the H2O—C2H6—NaCl and the H2O‐hexane‐NaCl systems computational descriptions of the isopleths, based on a “quasi‐binary” approach and a recently derived rational equation of state are given.

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The relative static dielectric constant or permittivity E and density e of t-butyl chloride was measured between 25 "C and 200°C and from 100 to 2000 bar. The high pressure cell, simultaneously applicable to determine E and e, is described. Sample densities range from 0.694 to 0.949 g.cm-'. At 25°C and from 100 to 600 bar E increases from 9.86 to 10.59. At 100°C between 100 and 2000 bar E ranges from 6.75 to 8.57. At 200°C from 200 to 2000 bar E grows from 4.12 to 5.69. Functions for E and e in dependence of pressure with fitted parameters are given. Calculated Kirkwood correlation factors g are presented, which exceed unity only moderately (from 1.03 to 1.22).A comparison is made with &-values of high pressure HCl and CH3Cl. IntroductionLiquids with polar molecules are good solvents, and the relative dielectric permittivity or dielectric constant is an important characteristic of such liquids. Knowledge of this property also contributes to the understanding of molecular interaction. The study of the dielectric constant over a wider range of temperature and pressure offers additional insight and may also open up new aspects for application. A comprehensive, satisfactory theoretical treatment of the dielectric behaviour of polar fluids which covers wide variations of molecular sizes, dipole moments, temperature, density and mixture conditions is not yet available. The classic state of the knowledge is reviewed and discussed by Bottcher [l].The dielectric constant of a number of fluids with small polar molecules has been studied experimentally in recent years in the supercritical range at high pressures. Among these fluids are NH3 [5], HCl [ 6 ] , CH3F [7], CHF3 [7], CH3Cl [S], CH30H [9], CHCIFz [lo], and CH2Cl2 [ll]. It was the aim of the present work to supplement the measurements with HCl [6] and CH3C1 [S] with the investigation of a fluid with molecules of similar structure but of larger size, namely tertiary butyl chloride, (CH3)3CCl. The dielectric constant values were to be combined with experimental density data. The region of temperatures and pressures should extend from 25 "C to 200°C and to 2000 bar. Earlier dielectric measurements with t-butyl chloride have been reported by Harris, Haycock and Alder [I23 and by Wilmers, Briese and Wurflinger [13]. The results of Harris et al. cover the range from 14°C to 50°C and pressures up to 200 bar. The work of Wilmers et al. was mainly concerned with the analysis of dielectric behaviour of the four different solid phases and the phase equilibria at temperatures below 40°C and at pressures up to 3000 bar. In the narrow range of overlap the agreement between the present results and those of Harris et al. and Wilmers et al. could be examined.