The new method of Pseudo-Static Ebuiliometer for deterdring osmotic co-efficients of nonaqueous electrolyte sohitions was developed at constan temperature. Aset of eaperimental apparatus was constructed. This apparatus was ctherited with NaCl,NaBr in methanol solvent. The results are consistat with the literature values, showingthat the apparatus is reliable and the accuracy is high also. The osmotic coefficients ofsolutions of Nal, Me4NCl, Bu4NBr in methanol solvent were measured at 298.15K. Theresults are fitted by Pitzer equation. The activity coefficients of salts in methanol are cal-ctilated using Pitzer’s interaction paramters obtained. The method is rapid, convenientand accurate, compared with the traditional static and isopiestic methods. It gives a pow-erful tool for measuxement of the osmotic coefficients of nonaqueous electrolyte solutions.
