An isopiestic method for measurement of electrolyte activity coefficients

Journal Article · Sun Nov 01 04:00:00 EST 1987 · A.I.Ch.E. J.; (United States)

DOI:https://doi.org/10.1002/aic.690331124· OSTI ID:5525867

Thiessen, D B; Wilson, A J

The need for greater efficiency and better water quality control in industrial plants has led to the development of process simulators for industrial water systems in recent years. The simulation of chemical equilibria in aqueous electrolyte systems was made possible by the work of others who have developed semi-empirical equations to predict activity coefficients in these solutions. These equations use single-component data along with interaction parameters to predict the behavior of mixtures. The development of accurate predictive equations for mixtures has been hindered by the lack of data on multicomponent solutions and single-component solutions at temperatures other than 25/sup 0/C. To obtain a desired accuracy in activity coefficient data from vapor pressure data, vapor pressure measurements must be obtained at a much higher degree of precision, as errors in vapor pressure measurement are amplified when converted to activity coefficients. One method capable of such accuracy for nonvolatile electrolytes is the isopiestic method. A modified isopiestic apparatus described herein allows visual determination of steady state and reduces the possibility of temperature gradients between solutions. Potassium chloride solutions were studied using NaCl as the reference solution. Vapor pressures determined with this apparatus were compared to the data of Robinson and Stokes (1965), giving an average absolute error of 0.008%. Pitzer's equation was fitted to the osmotic coefficient data, giving an average absolute error of 0.21% and standard deviation of 0.0009. The activity coefficients that were calculated from the experimental data compare favorably with those reported by others. The accuracy of the results obtained using the apparatus described demonstrates the temperature uniformity possible with a water bath.

• Research Organization: Dept. of Chemical Engineering, Univ. of Tulsa, Tulsa, OK 74104
• OSTI ID: 5525867
• Journal Information: A.I.Ch.E. J.; (United States), Journal Name: A.I.Ch.E. J.; (United States) Vol. 33:11; ISSN AICEA
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
320303* -- Energy Conservation
Consumption
& Utilization-- Industrial & Agricultural Processes-- Equipment & Processes
520200 -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
ACCURACY
ALKALI METAL COMPOUNDS
AQUEOUS SOLUTIONS
CHEMICAL REACTION KINETICS
CHLORIDES
CHLORINE COMPOUNDS
DISPERSIONS
ELECTROLYSIS
ELECTROLYTES
ENVIRONMENTAL QUALITY
HALIDES
HALOGEN COMPOUNDS
INDUSTRIAL PLANTS
KINETICS
LYSIS
MATHEMATICAL MODELS
MIXTURES
PHYSICAL PROPERTIES
POTASSIUM CHLORIDES
POTASSIUM COMPOUNDS
REACTION KINETICS
SODIUM CHLORIDES
SODIUM COMPOUNDS
SOLUTIONS
TEMPERATURE DISTRIBUTION
THERMODYNAMIC ACTIVITY
THERMODYNAMIC PROPERTIES
VAPOR PRESSURE
WATER QUALITY
WATER TREATMENT
WATER TREATMENT PLANTS