Determination of SrSO04 ion pair formation using conductimetric and ion exchange techniques |
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| Authors: | EJ Reardon |
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| Institution: | Department of Earth Sciences, University of Waterloo, Waterloo, Ontario, N2L3G1 Canada |
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| Abstract: | The dissociation constant for SrSO04 ion pair was determined at 25°C using conductance and ion-exchange techniques. Both approaches yield values for pK of SrSO04 at zero ionic strength in the range 2.28–2.31. Previously reported values range from 2.1 to 3.0. The refinement in the dissociation constant should allow more reliable appraisals of the extent of strontium mineral solubility controls on strontium concentrations in natural water systems.The Lee and Wheaton conductance model was used to interpret the results of the conductivity measurements in strontium sulphate solutions at 25°C. Because of the limitations imposed by the solubility of celestite, a sufficiently-wide concentration range to enable determination of all three of the parameters—dissociation constant, Λ0, and the distance parameter could not be made. Instead, values are reported for the dissociation constant and Λ0 using reasonable limiting values for the distance parameter.Dowex-50 was used in the ion-exchange technique to determine the dissociation constant for SrSO04. This method was used to determine values at other temperatures as well. Although there is considerable scatter in the temperature data, a standard enthalpy for the dissociation reaction: SrSO04→ Sr2+ + SO2?4 is computed to be 8.7 ± 2 kJmole?1 at 25°C. |
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