Mixtures equivalent conductance

In view of Swalin s treatment of diffusion in liquid metals, the latter seems to be a better description. In binary mixtures such as NaCl-KCl the equivalent conductivities are a linear manner, but the KCl-CdCl2 mixture shows a marked negative departure from linear behaviour, probably because of the formation of the complex ion CdCh. ... 

The CE behaviour of inorganic anions in water-methanol mixtures has also been extensively studied. The specific conductivity a of electrolytes was converted into equivalent conductivity by... 

Also, in this case, conductivity data were analyzed by Fuoss-On-sager-Skinner equations and limiting equivalent conductances A<> and association constants KA are collected in Table II together with physical properties of solvent mixtures. Furthermore, Table III shows ethanol and tert-butanol concentration in the mixture [ROH], the relevant dielectric constant c, and the pK of picric acid. 

The critical micelle contraction values were obtained using the conductance method from the usual equivalent conductance vs. the square root of concentration plots. The apparatus has been described before (21). About 20 experimental points were obtained for each cmc determination. No cmc could be detected above 20 wt % of acetone and 30 wt % of n-propanol. Surfactants were studied in water - - acetone mixtures at 298.15 K in water + n-propanol mixtures at 308.15 K for comparison purposes with other systems (12) (see the Discussion section). 

Fig. 4.107. Comparison of the concentration dependence of the equivalent conductivity of tetraisoamylammonium nitrate dissolved in water and in water-dioxane mixtures.

Fig. 4.109. Minimum in the curve for equivalent conductivity vs. concentration in the case of tetraisoamylammonium nitrate in a water-dioxane mixture of dielectric constant e = 2.56.

Fig. 4.120. The equivalent conductivity of HCI in methanol-water mixtures decreases with increasing alcohol content and reaches a minimum at about 80 mol % of alcohol. At this concentration, the abnormal mobility, i.e., the mobility of the HgO ion compared with that of the K ion (which is of similar size), is reduced almost to zero.

Consider, for instance, the electrical conductance of fused CdClj and KCl mixtures. If the equivalent conductivity of the mixtures (at a fixed temperature) were given by a simple additivity relation, then a linear variation of equivalent conductivity with the mole fraction of KCl should be observed (dashed line in Fig. 5.53). The straight line should run from the equivalent conductivity of pure liquid CdClj at a particular temperature to that of pure liquid KCl at the same temperature. Some binary mixtures of single ionic liquids do indeed exhibit the simple additivity implied by the dashed line of Fig. 5.53. 

Fig. 5.53. The variation of the observed equivalent conductivity of CdCl2-KCI mixtures as a function of the mole fraction of KCI. The dashed line corresponds to the variation that would be given bythe additivity behavior.

One can resort to similar explanations for departures from ideality in mixtures of simple ionic liquids. However, there are specific differences between the situation in fused salts and that in aqueous solutions. In pure liquid KCI, there is no concentration variable and therefore fused KCI has a single value of equivalent conductivity (at a particular temperature). The mean distance between the and CP ions cannot be altered, as it can be in aqueous solutions, by interposing varying amounts of solvent... 

Theoretical interpretation of the concentration dependence of equivalent conductivity for simple binary mixtures was first presented by Markov and Shumina (1956). It should be emphasized that this theory, even when considering simple structural aspects, represents rather a method of interpretation of the experimental data than a genuine picture of the structure of the melt. In molten salts generally only ions and not molecules are present, hence the conception of Markov and Shumina (1956) is to be considered also from this aspect. Their theory is based on the assumption that the electrical conductivity of a mixture of molten salts varies with temperature like pure components. In this respect, general character of the electrical conductivity dependence on composition, indicating the interaction of components in an ideal solution, could be expected. 

In a mixture of univalent salts of the type AX-BX, the following interactions should be present AA, BB, AXB, and BXA. The last two interactions are equal, thus they can be written as 2AXB. Considering that the probability of the interactions mentioned is proportional to their molar fractions, Markov and Shumina derived a relation for the composition dependence of the equivalent conductivity in a mixture of molten salts in the form... 

Fig. 7. The Equivalent Conductance of Tctraisoamyl Ammonium Nitrate in a 95.99 per cent Dioxane-Water Mixture at 25°.

With the series of transference numbers for mixtures of HCl and KC1 already referred to and conduct-ance values for the same solutions, values of An for the various mixtures were obtained by Langs worth. These were found to vary linearly with the mixing fraction, and could be extrapolated without error to yidd A iarK .. . the equivalent conductance of vanishingly small amounts of hydrogen Ion in... 

Figure 5.12 Equivalent conductance of the mixture NaCl/MgClj at 25"C for a total concentration of 0.5 mol/1 (C voC7i + versus the NaCl proportion...

The mixed cmc values for mixtures of DEFUMAC with a cationic hydrocarbon surfactant DTAC were determined by plotting equivalent conductivity versus the square root of concentration. The cmc values agreed reasonably well with cmc values calculated from the regular solution theory assuming an interaction parameter value of j8 = 1. The positive (3 value indicates a repulsive interaction between the two surfactants. Hence, the cationic-cationic surfactant mixture deviates more from the ideal regular solution theory than the cationic-nonionic system. 

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