Cation transference number

CATION TRANSFERENCE NUMBERS AND EQUIVALENT CONDUCTIVITIES (fi cm2 equiv.-1) IN AQUEOUS SOLUTIONS AT 25° C... 

Mauritz and Gray analyzed the IR continuous absorption of hydrated Na OH - and K OH -imbibed Nafion sulfonate membranes for the purpose of correlating this phenomenon to the current efficiency (cation transference number) of chlor-alkali electrochemical cells.In this case, the similar issue of OH ( defect proton ) conductivity is important. A distinct continuous absorption appeared in the spec-... 

Equation (8.14) demonstrates once more that the cation flux caused by the oxygen potential gradient consists of two terms 1) the well known diffusional term, and 2) a drift term which is induced by the vacancy flux and weighted by the cation transference number. We note the equivalence of the formulations which led to Eqns. (8.2) and (8.14). Since vb = jv - Vm, we may express the drift term by the shift velocity vb of the crystal. Let us finally point out that this segregation and demixing effect is purely kinetic. Its magnitude depends on ft = bB/bA, the cation mobility ratio. It is in no way related to the thermodynamic stability (AC 0, AG go) of the component oxides AO and BO. This will become even clearer in the next section when we discuss the kinetic decomposition of stoichiometric compounds. 

Table 12. Cation transference numbers of aqueous solutions of EuClt in various concentration ranges at 25° C...

Electrical conductance, cation transference number and activity coefficient of the halide systems are discussed on page 37. 

The formula (VI-29) is valid for any uni-univalent electrolyte. It is evident from this formula that the sign of the liquid junction potential and also the orientation of the diffusion double layer, in respect to the double layer at the electrodes, depends on the relative magnitude of the anion and cation transference numbers. Should the anion transference number exceed that of cation... 

Figure 5.5 Temperature dependences of apparent cationic transference numbers for EMIBF4, EMITFSI, BPBF4, and BPTFSI.

Self-diffusivity, cooperatively with ionic conductivity, provides a coherent account of ionicity of ionic liquids. The PGSE-NMR method has been found to be a convenient means to independently measure the self-diffusion coefficients of the anions and the cations in the ionic liquids. Temperature dependencies of the self-diffusion coefficient, viscosity and ionic conductivity for the ionic liquids, cannot be explained simply by Arrhenius equation rather, they follow the VFT equation. There is a simple correlation of the summation of the cationic and the anionic diffusion coefficients for each ionic liquid with the inverse of the viscosity. The apparent cationic transference number in ionic liquids has also been found to have dependence on the... 

INFLUENCE OF TEMPERATURE ON CATION TRANSFERENCE NUMBERS IN 0.01 N SOLUTIONS... 

TABLE XXXIII. CATION TRANSFERENCE NUMBERS IN CADMIUM IODIDE AT 18 ... 

The equivalent conductances and cation transference numbers of ammonium chloride at several concentrations at 25 are as follows fLongsworth, J. Am, Chem, Soc, 57, 1185 (1935)] ... 

The results are given in Table III. It will be seen that using a silver anode the uncorrected cation transference number is about two per cent higher, for the more concentrated solution, than that found with a cadmium anode, whereas the corrected values differ by less than 0.1 per cent. It thus seems entirely probable, from these two lines of evidence, that this manner of making corrections for solvent displacement leads to correct results. 

Table IV. Cation Transference Numbers at 25° for Aqueous Solutions of Electrolytes Determined by the Moving Boundary Method...

Table VII. Cation Transference Numbers of Cadmium Iodide Solutions at 18° C.1...

Table VIII. "True and Hittorf Cation Transference Numbers and Transference of Water for a Series of Chlorides, at 1.3 Normal...

An illustrative computation from Des Coudres results is as follows. He found 0.510 x 10 volt for the ratio E/h for 2.71 molal potassium chloride. Multiplying the product EF/h by 101 to reduce it to absolute units, and dividing by the value 980.7, also in absolute units, for g, the acceleration due to gravity, yields 5.02 grams. The values of the other terms in equation (8a) are Voi, = 18.36 cc., t aci - 31.3 cc. and p = 1.111. From these figures and the molecular weights equation (8a) gives the value 0.50 for the cation transference number of potassium chloride. If the same values of the transference number are obtained as are found by other methods it is evident that a correct analysis of the mechanism of the process has been made. Such a comparison is made in Table I. The values of the... 

Solution Molality of solution m Emf, volts per centimeter height, X10 ——Cation Transference Number. Gravity Hittorf method method Reference... 

The variation of the cation transference number with the concentration for electrolytes of higher valence type is given by the equation15... 

Sulphuric Acid and Related Compounds. The vibrational spectra of H2SO4 and D2SO4 in the crystalline state have been measured at various temperatures. The cation-transference numbers of Li, Na, K, NH3, Ag, and Ba hydrogen sulphates, and of solutions of water and acetic acid, have been measured in 100% H2SO4 at 25 °C. The numbers obtained were of the order of 0.005, much smaller than was previously believed. The behaviour of hafnium dioxide and copper(ii) oxide in sulphuric acid has been studied and various compounds have been isolated. 

Electrolyte Solutions. IV. Determination of Cationic Transference Numbers in Methanol, Ethanol, Propanol, and Acetonitrile at Various Temperatures., Ber. Bunsenges. Phys. Chem., 1982, 86, 636. 

TABLE 2.3.1 Cation Transference Numbers for Aqueous Solutions at 25°C"... 

The ionic conductivity is due to both cation and anion species. The cationic transference number = (o / o. ). The anionic transference number x = 1 - x. Different ionic and electronic contributions to the total conductivity can be measured by an electrolysis experiment with the use of selective blocking electrodes which is for blocking all the conducting ion species but the desired one [16, 22].This is a direct current (d.c.) experiment. 

Fig. 5. Temperature- and concentration-dependence of cationic transference numbers of methanol solutions of M64NSCN (o) and KSCN (O) The full lines are computer plots according to the set of Eqs. (37)...

The nature of the mobile ionic species was questionable for a long period of time. For passive Al, Verwey [47] assumed in 1935 that exclusive transport of Al-cations occurs in a fixed oxygen matrix. The idea of mobile cations dominated the oxide formation theories for the next 30 years. It seemed to be reasonable, as the volumes of cations are much smaller than -anions (e.g. by a factor of 20 for AP+), even if the experimental results indicated a combined transport. Marker experiments in the sixties proved cation-transference numbers in the range from 0.3 to 0.7 for many systems (Al, Be, Nb, Ta, Ti, V, W) coming closer to 0.5 with increasing current density, that is, cations and anions move in fact simultaneously (Table 1). This indicates that effects of charge distribution become more important than individual ion properties like size or polarizability [25]. Exceptions are the crystalline oxides on Hf and Zr, which are pure oxygen conductors. 

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