Stability of the calcium sulphate ion pair at the ionic strength of seawater by potentiometry |
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Authors: | Bengt Elgquist Margareta Wedborg |
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Affiliation: | Department of Analytical Chemistry, University of Göteborg, Göteborg Sweden |
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Abstract: | The stability of the ion pair CaSO4 was determined from measurement of the change in calcium ion activity with medium composition at constant ionic strength. A calcium selective PVC-matrix liquid membrane electrode was used to monitor the calcium ion activity. All measurements were performed at 1 atm, 25 ± 0.1°C and 0.7 M formal ionic strength. The evaluation of the stability constant depends on the degree of complexation between calcium and chloride and between sodium and sulphate. The dependence of KCaSO4, on KNaSO4 and KCaCl can be described by the following relations:KCaSO4=17.7 KCaCl+16.5 (KNaSO4=1.8)KCaSO4=18.8 KCaCl+17.3 (KNaSO4=2) for KCaCl=0–1A value of KCaSO4=25.4 is suggested. |
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Keywords: | To whom correspondence should be addressed. |
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