Isopiestic determination of osmotic coefficients and evaluation of vapor pressures for solutions of KI, NH 4SCN and KSCN in methanol at 25 °C

Abstract

The osmotic coefficients of potassium iodide, ammonium thiocyanate and potassium thiocyanate in methanol have been measured by the isopiestic method at 25 °C. Sodium iodide utilized as an isopiestic standard for the calculation of osmotic coefficients. The molality ranges covered in this study correspond to approximately 0.1–1 mol kg −1 for KI, 0.2–4.4 mol kg −1 for NH 4SCN and 0.12–2.69 mol kg −1 for KSCN. Experimental osmotic coefficient data are reliably represented by the Clegg–Pitzer and Pitzer–Mayorga models. The parameters from the fit were used to calculate the vapor pressures. The osmotic coefficient data are successfully correlated with this model, and the model demonstrates a reliable predication of vapor pressures.