Concentration cation effect

PE permeability was enhanced by CaCl2 at lower concentrations than effective for NaCl. Pi8o in O.IM CaCL was approximately 0.33, and similar to the permeability in 0.4M NaCl at pH 3.8. There seems to be a unique cation effect rather than ionic strength effect. At equivalent ionic strength (0.3M NaCl and O.IM CaCl2, pH 3.8), Pjso of PE with CaCl2, was approximately four fold higher. 

Campion, R. J. Deck, C. F. King, P., Jr. Wahl, A. C. Inorg. Chem. 1967, 6, 672]. The cation effect was tremendous—spanning two or three orders of magnitude—and occurred at low concentration levels. 

However, if the valences of the exchanging cations are equal, the selectivity coefficient or pseudo-equilibrium constant is not affected by concentration. As already mentioned, one isotherm corresponds to a specific temperature in the case of adsorption or ion exchange of equal valence ions, whereas additionally, the same normality is required for the existence of only one isotherm in the case of ion exchange of different valence ions, due to the concentration-valence effect (Helfferich, 1962). The determination of the true equilibrium constant should be based on the thermodynamic activities (activity coefficients) of the species rather than concentrations. It is clear that the difficulties in the determination of activity coefficients also complicate the determination of the true equilibrium constant (Culfaz and Yagiz, 2004). 

Tan, Z., and Chen, S. (2006). Nucleic acid helix stability Effects of salt concentration, cation valence and size, and chain length. Biophys.J. 90(4), 1175-1190. 

The limiting current density is determined by concentration-polarization effects at the membrane surface in the diluate containing compartment that in turn is determined by the diluate concentration, the compartment design, and the feed-flow velocity. Concentration polarization in electrodialysis is also the result of differences in the transport number of ions in the solution and in the membrane. The transport number of a counterion in an ion-exchange membrane is generally close to 1 and that of the co ion close to 0, while in the solution the transport numbers of anion and cations are not very different. 

Nonetheless, sensitization by dyes held within the cores of microemulsions can be easily accomplished [69]. Such sensitization is an important component of photogalvanic effects, the magnitude of which are significantly enhanced in the non-homogeneous environment of a microemulsion [70], The hydrophilic core of an water-in-oil microemulsion can concentrate cation radicals formed via interfacial electron transfer and hence increase the yield of subsequent dimerization the dimethylnaphthalene cation radical exhibits a dimerization equilibrium constant of nearly 500 in a microemulsion [71]. For similar reasons, hexylviologen acts as a much more efficient relay than methyl viologen in a CTAB/hexanol microemulsion [72]. 

Electrolytes affect dispersed polysaccharides through water inactivation, specific ion binding, and polyanion neutralization. Each effect is valence-dependent, but is less on neutral polysaccharides than on ionic polysaccharides. Di- and polyvalent cations gel or precipitate a constant amount of polysacchride at much lower concentrations than do monovalent cations. The precipitation reaction is used to advantage in isolating pectin with alkaline Al3+, because this cation and polymeric forms of Al(OH)3 readily precipitate and entrain pectinic acid from apple tissue homogenates. Other di- and polyvalent cation effects are crosslinking (Prud homme et al., 1989) and an increased rate of (3 elimination over monovalent cations (Sajjaanan-... 

A completely different situation occurs for mica surfaces, for which both charges and dipoles are present on the surface. For these surfaces, strong specific cation effects have been observed experimentally at relatively low electrolyte concentrations [17]. These specific ion effects cannot be explained by the additional interactions between ions (such as excluded volume effects) or ions and surfaces (such as ion-dispersion [9] or ion-hydration [10] forces), because these interactions are in general negligible for electrolyte concentrations smaller than about 0.05 M. 

Yawalata, D. and Paszner, L., Cationic effect in high concentration alcohol organosolv pulping The next generation biorefinery. Holzforschung 2004, 58 (1), 7-13. 

Excellent antistat for all fibers--effective at low use concentrations--cationic. 

Shimizu and Oku (1957) studied the effects of salts on the solubility of wool in 0.1 M KOH. At low salt concentrations the effects of various ions followed the Hofmeister series. Similarly, McPhee (1958b, 1959) has shown that whereas 56 % of wool was dissolved by 1.286 N NaOH at 25°C in 2 hr, only 2 % dissolved when the solution was first saturated with NaCl. There was a corresponding decrease in formation of primary amino groups and in loss of cystine. Not all salts were equally effective in protecting wool against alkali damage. The effectiveness of 2 M solutions of the sodium salts decreased in the order 8203 > SO3 > citrate > COs" > SO 4 > acetate > Cl > Br > NOs" > I > CNS . Cations followed the order Li+, Na+ > K+. Similar rates of alkali uptake were obtained with all salts at a concentration oi 2 M. 

The area of cyclopropylvinyl cation chemistry has been recently reviewed in detail by Stang and coworkers " and thus will only be summarized here. The majority of the studies subsequent to the initial report have concentrated on effects of the nature and of the stereochemistry of substituents on the double bond or on the cyclopropane ring on the rates of solvolysis and product ratios °. A typical example of the product forming-behavior from a cyclopropylvinyl system is given below. ... 

Since oxygen is one of the products of electrolysis, if the electrolytic cell is undivided, reoxidation of U " ion takes place which hampers the production of uranyl with higher concentration. Cation-selective membrane spacers are effective in improving the production of uranyl nitrate solution. 

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. 

---