An isopiestic method for measurement of electrolyte activity coefficients
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), Vol. 33:11
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
54 ENVIRONMENTAL SCIENCES
ELECTROLYTES
CHEMICAL REACTION KINETICS
THERMODYNAMIC ACTIVITY
INDUSTRIAL PLANTS
WATER QUALITY
POTASSIUM CHLORIDES
VAPOR PRESSURE
WATER TREATMENT PLANTS
ACCURACY
AQUEOUS SOLUTIONS
ELECTROLYSIS
MATHEMATICAL MODELS
SODIUM CHLORIDES
TEMPERATURE DISTRIBUTION
WATER TREATMENT
ALKALI METAL COMPOUNDS
CHLORIDES
CHLORINE COMPOUNDS
DISPERSIONS
ENVIRONMENTAL QUALITY
HALIDES
HALOGEN COMPOUNDS
KINETICS
LYSIS
MIXTURES
PHYSICAL PROPERTIES
POTASSIUM COMPOUNDS
REACTION KINETICS
SODIUM COMPOUNDS
SOLUTIONS
THERMODYNAMIC PROPERTIES
320303* - Energy Conservation
Consumption
& Utilization- Industrial & Agricultural Processes- Equipment & Processes
520200 - Environment
Aquatic- Chemicals Monitoring & Transport- (-1989)