The instability constant of a substance shows the tendency of a substance to dissociate into simple ions. The stability of the substance can be related to stabilities of other substances through the instability constant. Schubert gives a method for the determination of the instability constant which involves measurements of the adsorption of a radiotracer cation on a cation exchange resin. Two different types of resin were employed in this research. It was found that with a resin containing carboxylic acid exchange groups the adsorption of the cobaltous ion changed rapidly with pH but with a resin containing nuclear sulfonic acid as the exchange group, the adsorption of the cobaltous ion changed very little with pH. The presence of an exchange resin in an equilibrium presents the problem of activity of the resin. Boyd's approach to the activity of the resin using the law of mass action was applied to the resin and cations used in this research. The data obtained in this research supported Boyd's approach to the activity of resins. The activity coefficients of the ions in solution were calculated using the Debye Huckel theory. Measurements of actual activity coefficients were not taken. Schubert's method was applied to two complex ions of cobalt using cobalt-60 as a tracer. The pK of the instability constants of the cobaltous citrate and cobaltous oxalate complex ions were determined to be 6.39 and 4.61 respectively. Hydrolysis of the complexing anion into an inactive form changed the pK of the instability constant of the oxalate complex ion 1.5 per cent and the citrate complex ion 7.8 per cent. Precautions were taken at all times during this research to avoid the dangers of radiation to personnel and equipment.



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Chemistry and Biochemistry



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