Liquid-liquid equilibrium data for the PEG 4000 + NaNO 3 + H 2 O system were measured at 298.15 K. The binodal curve was fitted to a three-parameter equation, and the tie line compositions were fitted to both the Othmer-Tobias and Bancroft equations. The refractive indices and densities of several homogeneous ternary solutions used for calibration were also measured in the range 0-40 mass % PEG, 0-18 mass % NaNO 3 .

Liquid−liquid equilibria for the poly(ethylene glycol) (PEG) + NaNO3 + H2O system, with PEG of molecular weights 2000, 6000, and 10 000, have been measured at 298.15 K. The binodal curve was fitted using a three-parameter equation, and the compositions of the tie lines at equilibrium were fitted using the Othmer−Tobias equation. These equations were used to develop a mathematical model for interpretation of the equilibrium data of these aqueous two-phase systems (ATPS's). Data on the densities and refractive indexes are also given for the solutions at equilibrium. It was found that an increase in the molecular weight of the PEG produced a displacement of the binodal curve toward the origin and increased the liquid−liquid biphasic zone. The ATPS's studied may be used in separation of iodine and other compounds.

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Liquid−liquid and solid−liquid equilibrium data are presented for the PEG 4000 + Na2SO4 + water system at 298.15 K. Six equilibrium regions were found. The binodal curve was fitted by means of a three-parameter equation (relative mean deviation 3.95%), and the tie lines compositions were fitted to both the Othmer−Tobias and Bancroft equations. Densities and refractive indices were determined for the solutions in equilibrium. Samples of the solid phase analyzed by X-ray diffraction showed it to consist of anhydrous Na2SO4.