Some Aspects on the Problem of Individual Activity Coefficients of Single-ion Species of Aqueous Strong Electrolytes

Abstract

Individual activity coefficients of single-ion species can neither be defined in thermodynamic terms nor determined experimentally. This does not mean that the individual activity of a single-ion species of an aqueous strong electrolyte does not have a real specifically individual effectiveness. Individual ion activity coefficients are required, for instance, for data about the potentials of single electrodes and liquid junction potentials in galvanic cells with transference. A purely mathematical method is written which allows the factorizing the mean activity coefficient into individual parts of the single-ion species. The experimentally accessible concentration curve of the mean activity coefficient is fitted with a quite new mathematical approach. The parameter set of the mathematical approach can be determined univocally and invariantly with the help of the asymptotic theory using corresponding approximations.Keywords: aqueous strong electrolytes, concentration dependence of activity coefficients, factorization of the mean activity coefficients, individual ion activity coefficients IntroducationThe analytical concentration "m" of a component within a real and homogeneous mixed phase has to be modified for the thermodynamic interpretation of equilibriums, according to Eq. (1):The modified concentration "a" is denoted as activity. The multiplicative term "γ" is known as activity coefficient. The activity coefficient considers all deviations from ideal behaviour of the component within the real mixed phase by forming of interaction forces.