Ionic strength acid transition

Although these effects are often collectively referred to as salt effects, lUPAC regards that term as too restrictive. If the effect observed is due solely to the influence of ionic strength on the activity coefficients of reactants and transition states, then the effect is referred to as a primary kinetic electrolyte effect or a primary salt effect. If the observed effect arises from the influence of ionic strength on pre-equilibrium concentrations of ionic species prior to any rate-determining step, then the effect is termed a secondary kinetic electrolyte effect or a secondary salt effect. An example of such a phenomenon would be the influence of ionic strength on the dissociation of weak acids and bases. See Ionic Strength... 

It is possible to control the pressures at which the phase transitions occur by fine tuning the strength of intermolecular interactions between the amphiphilic molecules. The interactions between the hydrophobic tails depend on temperature [37], while the interactions between the hydrophilic heads depend on the chemical composition of the subphase, namely its pH and ionic strength [4], For example, the fatty acid molecules in films prepared on subphase with high pH and high concentration of divalent salt, such as CaCl2 or CdCl2, are normal to the surface, i.e. are in solid state, even at low pressures. Pressure-area isotherms of such films are featureless compressed films are stable and easy to transfer [38]. 

A whole range of cations and anions in different combinations have been explored. The results are surprising. Measurements of coalescence rates for a range of typical electrolytes as a function of electrolyte concentration are shown in Fig. (3.5). There is a correlation between valency of the salt and transition concentration, defined as 50% bubble coalescence, with more highly charged salt effective at lower concentration. The effect is independent of gas flow rate. All the results scale with Debye length (ionic strength). Some salts and acids have no effect at all on bubble coalescence, a situation summarised in Table 3.1. 

A kinetic electrolyte effect ascribable solely to the influence of the ionic strength on activity coefficients of ionic reactants and transition states is called a primary kinetic electrolyte effect. A kinetic electrolyte effect arising from the influence of the ionic strength of the solution upon the pre-equilibrium concentration of an ionic species that is involved in a subsequent rate-limiting step of a reaction is called a secondary kinetic electrolyte effect. A common case encountered in practice is the effect on the concentration of a hydrogen ion (acting as catalyst) produced from the ionization of a weak acid in a buffer solution. 

Water-soluble poly(acrylic acid)-based nanocapsules with reversible pH- and ionic strength-dependent swelling transition were prepared by Meier et al. [224], During this transition gated pores in the spherical polymer shells are opened (closed), which enables free molecular exchange between the interior of the hollow sphere and the bulk medium. This pH-switchable control of permeability can trigger release of encapsulated cargo from the polyelectrolyte spheres. 

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