High Pressure Supercritical PVT-Data of Water-Sodium Hydroxide Mixtures and of Liquid Sodium Hydroxide to 673 K and 400 MPa

摘要

The density of homogeneous fluid mixtures of water and sodium hydroxide has been measured from 293 to 673 K and at pressures from 10 to 400 MPa. Measurements were performed at eight compositions between 10 and 90 weight percent NaOH and with pure molten NaOH. At sufficiently high pressure complete miscibility of NaOH and H_2O exists above the melting temperature of NaOH at 595 K. A differential autoclave with internal heating within a space filled with high pressure argon and with an internal nickel bellows cell for the H_2O-NaOH mixtures is described. Immediate results are given as specific mixture volumes and molar volumes. Molar volumes in dependence of composition have distinct minima near 30 mole percent NaOH. All excess volumes are negative. A semiempirical equation is proposed on the basis of a hydration model to describe molar and excess volumes. Partial molar volumes and estimated activity coefficients are given for 673 K and pressures at 100 and 400 MPa.