The densities and viscosities of binary and ternary solutions of the aqueous two-phase systems created by the polyethylene glycol 6000 + triammonium citrate + water system were measured at different temperatures (25, 30, 35, 40, and 45) °C and correlated with empirical equations. The density data were compared with those available in the literature. The density data show a linear variation with the mass fraction of the polymer for all temperatures. The density and viscosity of the top and bottom phases were also measured and reported. © 2009 American Chemical Society.