Some new algorithms applicable to potentiometric titration in acid-base systems.
The paper describes some regression equations adaptable for determination of parameters such as concentrations, equilibrium constants and hydrogen-ion activity coefficients in systems comprising hydrolysable salts of type MeB(u) and monoprotic and polyprotic acids or their salts. These equations are based on the charge and mass balances. Two unconventional types of regression equations are applied: (i) Padé functions W = G(1)(h)/G(2)(h) relating the sum (W) of V(0) ml of titrand and V ml of titrant, W = V(0) + V, to polynomial functions G(1)(h) and G(2)(h) of the hydrogen-ion activity, h, and (ii) functions of the type 1/W = phi(h), based on the Simms titration constants involved. The latter functions are notable for determination of acids and/or their salts in mixtures. The regression equations are developed for systems at constant ionic strength. The parameters of the system can be calculated by means of the computer program MINUITS. Other possibilities of the method, e.g., application to mixed complexes and extraction systems, are also presented.
Michałowski
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Department of Analytical Chemistry, Faculty of Chemistry, Jagiellonian University, 30-060 Kraków, Poland.