Volumetric, isentropic compressibility and electrical conductivity of solutions of tri-sodium phosphate in 1-propanol + water mixed-solvent media over the temperature range of 283.15–303.15 K

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Abstract

Density, sound velocity and electrical conductivity of solutions of tri-sodium phosphate (Na3PO4) in 1-propanol + water mixed-solvent media with alcohol mass fractions of 0.00, 0.05, 0.10, and 0.15 are reported in the 283.15–303.15 K temperature range at 5 K intervals. From the experimental density and sound velocity data, the apparent molar volume and isentropic compressibility values of tri-sodium phosphate are evaluated and fitted to a Redlich + Meyer type equation from which the apparent molar volume and apparent molar isentropic compressibility of the solutions at the infinite dilution are calculated at working temperature. The results show a positive transfer volume of Na3PO4 from an aqueous solution to an aqueous 1-propanol solution. The apparent molar isentropic compressibility of Na3PO4 in aqueous 1-propanol solutions is negative and it increases with increasing concentration of Na3PO4, 1-propanol and temperature. The effects of the electrolyte concentration, temperature and relative permittivity of the medium on the molar conductivity are also investigated. Comparisons between the results obtained in this work are made with those for Na2HPO4 and NaH2PO4 obtained in our previous works.

Introduction

The salt in mixed solvent plays an important role in scientific research and the chemical industry, such as recycling of organic solvent in a mixed-solvent system, design of extractors, separation of mixtures, biological process, etc. Thermodynamic properties of mixed-solvent electrolyte systems are necessary for a fundamental understanding of the phase-forming ability and also for the development of theoretical models for design and simulation of these processes. Studies on the volumetric and conductometric studies of electrolytes in different mixed solvent systems are of great importance to obtain information as to the solvation and association behavior of ions in solutions.

In continuation of our previous works on the volumetric properties of phosphate salts in aqueous 1-propanol solutions [1], [2], here we present our results on density, sound velocity and conductometric measurements of tri-sodium phosphate in 1-propanol + water mixed-solvent media containing 0.00, 0.05, 0.10, and 0.15 mass fractions of 1-propanol at various temperatures. Although there are some very limited reports on the density [3], [4], [5] and electrical conductivity [6], [7], [8] of binary aqueous Na3PO4 solutions, however there are no experimental data on the ultrasonic velocity of aqueous solutions of Na3PO4 at different temperature in the literature. Furthermore, volumetric, isentropic compressibility and conductometric behavior of Na3PO4 in aqueous 1-propanol solutions are scarce.

Section snippets

Materials

1-Propanol was obtained from Merck (GR, min 99.5%). Tri-sodium phosphate (Na3PO4·12H2O) was obtained from Merck (GR, min 99.5%). The alcohol and salt were used without further purification, and double distilled, deionized water was used.

Apparatus and procedures

All the solutions were prepared by mass on a Sartorius CP124S balance precise to within ±0.0001 g. The density and sound velocity of the mixtures were measured at different temperatures with a digital vibrating-tube analyzer (Anton Paar DSA 5000, Austria) with

Results and discussion

Density (d) and sound velocity (u) values for various Na3PO4 solutions determined at T = 283.15, 288.15, 293.15, 298.15 and 303.15 K are given in Table 1. Experimental data of molar conductivity (Λm) for investigated systems at T = 283.15, 288.15, 293.15, 298.15 and 303.15 K are given in Table 2. The following equation has been used for the correlation of experimental density and ultrasonic velocity data:F=P1expP2+P3wsP4wa+P5T+P6where ws and wa are the mass fraction of the salt and alcohol,

Conclusions

Experimental data at T = 283.15–303.15 K of density, sound velocity and electrical conductivity of tri-sodium phosphate in water + 1-propanol mixed-solvent media containing 0.00, 0.05, 0.10, and 0.15 mass fractions of 1-propanol have been reported. The values of apparent molar volumes and isentropic compressibilities of solutions were calculated from the measured data. The results show a positive transfer volume of tri-sodium phosphate from an aqueous solution to an aqueous 1-propanol solution. The

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