Electrolyte in mixture with a neutral component: effects of counterion charge

Abstract

The equilibrium structure and thermodynamics of a multicomponent primitive model mixture consisting of a single asymmetric electrolyte and a neutral particle are studied as a function of the concentration of the neutral species, and for counterion valencies − 1,− 2 and − 3. The model, relevant for 'crowding reaction' processes in many biological systems is considered within the context of the symmetric Poisson–Boltzmann, the modified Poisson–Boltzmann, and the hypernetted chain theories. An important common prediction of the theories is that, at higher concentrations of the neutral species and for all valencies, there is an attractive force between the macroions. A comparison of the pair distribution functions and thermodynamics reveals the theories to be in semiquantitative or better agreement overall, with the modified Poisson-Boltzmann and the hypernetted chain results being generally closer to each other.