The Osmotic Pressure of Concentrated Solutions of Polyethylene Glycol 6000, and its Variation with Temperature

Abstract

The vapour pressures of aqueous solutions of polyethylene glycol 6000 have been measured (by equilibration with sucrose solutions) up to the saturation point at 25 °C (1.45 g g⁻¹ water). The reduced-osmotic-pressure (π/c), when plotted versus concentration (c), rapidly and linearly increased up to a concentration of about 0.8 g g⁻¹ (crossing the similar plot for sucrose). Above this concentration, the reduced-osmotic-pressure rose more slowly, but still more rapidly than sucrose. The maximum osmotic pressure achieved at saturation was nearly 18 MPa. Using the virial equation: π/c= RT/M + RTA₂c, the calculated second virial coefficient (A₂) for the linear part is 4.5 × 10⁻³ mol g⁻¹, a value slightly greater than most literature values at 25 °C. Data are cited showing that A₂ varies linearly from 5–6 × 10^×3 at 0 °C, to zero at 80–90 °C