Studies on the second virial coefficient of sodium alginate solution

Based on the measurement of the concentration dependence of the osmotic pressure of sodium alginate aqueous solution in different concentrations of potassium nitrate, the contribution of polyion charges to the second virial coefficient was predicted. According to this analysis, an equation A2=A2, O+A2, Dwas obtained, and a method was introduced to determine the θ‐point of polyelectrolyte solution from A2determined by membrane osmometry. This is important in the investigation field of polymer solution theory and was proved to be correct if each polyelectrolyte molecule was ionized completely. The θ‐solvent of sodium alginate aqueous solution was measured to be the concentration in 1.41 molar potassium nitrate per litre at 30°C, and this experimental result indicated that Manning's polyelectrolyte solution theory model is fairly successful in explaining the colligative properties of polyelectrolyte solution. © 1997 John Wiley & Sons, Ltd.