Force ionic strength dependence

Recognizing the ionic strength dependence of the effect of short range forces in binary interactions, Pitzer was able to develop an empirical relation for B,-a(I). The expression for systems containing strong electrolytes with one or both ions univalent is... 

Pitzer (9) recently has developed a system of equations for electrolyte thermodynamics which yields comparable results to the Guggenheim-Scatchard equations for both single and mixed electrolytes. The main feature of the Pitzer equations is that they include an ionic-strength dependence on the short-range forces in binary interactions. 

Table 6 lists association constants between porphyrins and nucleic acids. Equilibrium constants between Hi(TMpyP-4) (52) and Cu(TMpyP-4) (88) with a synthetic polymer poly(dG-dC) were estimated to be 7.7 x lO M and 8.0 x 10 M, respectively, based on McGhee-von Hippel analysis.The equilibrium constants were ionic-strength dependent. It was observed that at 2 M ionic strength, the Free-base poqrhyrin 52 almost completely dissociates from DNA, poly(dA-dT) and poly(dG-dC). Therefore electrostatic interactions are the important driving force. Kinetic studies were carried out for the above system... 

In 1973, Pitzer el al. began presenting a series of papers (PI - P12) reporting their development of a system of equations for electrolyte thermodynamic properties. In expanding the Debye-Htickel method, terms were added to account for the ionic strength dependence of the short-range forces effect in binary interactions. 

However, in subsequent studies [23-25,88-90] it was demonstrated that in reality the particle deposition is not a purely geometric effect, and the maximum surface coverage depends on several parameters, such as transport of particles to the surface, external forces, particle-surface and particle-particle interactions such as repulsive electrostatic forces [25], polydispersity of the particles [89], and ionic strength of the colloidal solution [23,88,90]. Using different kinds of particles and substrates, values of the maximum surface coverage varied by as much as a factor of 10 between the different studies. 

At a finite distance, where the surface does not come into molecular contact, equilibrium is reached between electrodynamic attractive and electrostatic repulsive forces (secondary minimum). At smaller distance there is a net energy barrier. Once overcome, the combination of strong short-range electrostatic repulsive forces and van der Waals attractive forces leads to a deep primary minimum. Both the height of the barrier and secondary minimum depend on the ionic strength and electrostatic charges. The energy barrier is decreased in the presence of electrolytes (monovalent < divalent [Pg.355]

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