Ionic characterization factor

Dankwerts and McNeil ( 3) have employed the method of Van Krevelen et al. to predict the partial pressure of carbon dioxide over carbonated alkanolamine solutions. The central feature of this model is the use of pseudo-equilibrium constants and their dependence on ionic strength. The ratio of the pseudo-equilibrium constant at a certain ionic strength to that at zero ionic strength has been termed the "ionic characterization factor". However, ionic strength alone is insufficient to determine the ionic characterization factors. As well the ionic characterization factors are sometimes not a simple linear function of ionic strength. 

Kent and Eisenberg (5) also correlated solubility data in the system S+CC +alkanoleimines+ O using pseudo-equilibrium constants based on molarity. Instead of using ionic characterization factors, they accepted published values of all but two pseudoequilibrium constants and found these by fitting data for MEA and DEA solutions. They were able to obtain excellent fits by this approach and also discovered that the fitted pseudo-equilibrium constants showed an Arrhenius dependence on temperature. 

Calculations for Rp as a function of the relevant experimental parameters (eluant ionic species concentration-including surfactant, packing diameter, eluant flow rate) and particle physical and electrochemical properties (Hamaker constant and surface potential) show good agreement with published data (l8,19) Of particiilar interest is the calculation which shows that at very low ionic concentration the separation factor becomes independent of the particle Hamaker constant. This result indicates the feasibility of xmiversal calibration based on well characterized latices such as the monodisperse polystyrenes. In the following section we present some recent results obtained with our HDC system using several, monodisperse standards and various surfactant conditions. 

Influence on Electrolyte Conductivity In porous separators the ionic current passes through the liquid electrolyte present in the separator pores. Therefore, the electrolyte s resistance in the pores has to be calculated for known values of porosity of the separator and of conductivity, o, of the free liquid electrolyte. Such a calculation is highly complex in the general case. Consider the very simple model where a separator of thickness d has cylindrical pores of radius r which are parallel and completely electrolyte-filled (Fig. 18.2). Let / be the pore length and N the number of pores (all calculations refer to the unit surface area of the separator). The ratio p = Ud (where P = cos a > 1) characterizes the tilt of the pores and is called the tortuosity factor of the pores. The total pore volume is given by NnrH, the porosity by... 

The solution structure of a thioredoxin from B. acidocaldarius (Topt = 60 °C) has been studied by NMR and compared with that of E. coli determined by X-ray analysis. It was found that the higher thermostability of the former is due to cumulative effects, the main factor being an increased number of ionic interactions cross-linking different secondary structural elements. Multidimensional heteronuclear NMR spectroscopy was also employed to characterize thioredoxin homologues found in the hyperthermophilic... 

A more detailed characterization of the interactions is obtained by calculating the equilibrium constants according to Eq. (2). By fitting (parameters KP and v, CMC = const.) Eq. (2) to the experimentally obtained values (measured ionic mobility of drug -> kP (capacity factor)/concentration gra-... 

It is notable that the structure factors, proportional to the scattered intensity, for gels could be very different between gels composed of non-ionic neutral polymers and of ionized polymers. In the case of the non-ionic gels, the structure factor is characterized by the screening length of the polymer chains, which is the so-called correlation length, On the other hand, an additional screening... 

Mixtures of equisized charged spheres were also treated by the MSA. Such a system is then uniquely characterized by the ratio of the critical temperatures of the pure components. Harvey [235] found that a continuous critical curve from the dipolar solvent to the molten salt is maintained until the critical temperature of the ionic component exceeds that of the dipolar component by a factor of about 3.6. This ratio is much higher than theoretically predicted for nonionic model fluids. We recall that for NaCl the critical line is still continuous at a critical temperature ratio of about 5. Thus, the MSA of the charged-hard-sphere-dipolar-hard-sphere system captures, at least in part, some unusual features of real salt-water systems with regard to their critical curves. 

The development of the first transdermal patches in the 1980s generated considerable interest in this route of drug administration. Soon afterwards, iontophoresis was rediscovered and its potential to contribute to the new field of transdermal drug delivery was examined. This work provided the basic principles for modern iontophoretic devices [13,18-21]. Furthermore, and importantly, they demonstrated the existence of a (primarily) electroosmotic, convective solvent flux during transdermal iontophoresis [10,11,22-24], and it was shown that the permselective properties of the skin (a) could be exploited to enhance the transport of neutral, polar species and (b) have a clear impact on ionic transport. Subsequent research has better characterized skin permselectivity and the factors which determine the magnitude of electroosmosis [25-27],... 

---