Data are presented on the refractive index, density, and viscosity of unsaturated solutions of sodium nitrate + poly(ethylene glycol) + water at six temperatures between (15 and 40) degreesC. The range of concentration of the solutions was from (3 to 24) mass % of NaNO3 and from (3 to 24) mass % of poly(ethylene glycol) (PEG) with an average molecular weight of 4000. The Othmer rule was used to obtain correlations between experimental data and the three parameters studied. Data are also presented on the excess molar volumes (V-E) of this system for different compositions and working temperatures.