The pseudo-capacity and over-all polarisation resistance during the electroreduction of tervalent bismuth at a dropping-mercury cathode in various media were traced as a series combination; and the general features of the former are described. The combination corresponding to the peak values was then balanced against the equivalent of a simple model of the faradaic admittance, and in this way information was obtained from which the specific rate constant for the above exchange in each medium could be evaluated. In N-perchloric and N-hydrochloric acid, the results agreed excellently with those previously published. In N-nitric and N-sulphuric acid the constants were respectively 3.7 x 10-3 and 1.8 x 10-3 cm. sec.-l a t 26" f 0.5". In mixtures of nitric and perchloric acid of constant ionic strength, the rate increased sensibly with the increase of concentration of the former. The order of reactivity towards electron transfer for the various anions is briefly discussed in the light of possible ionic interactions within the electrical double layer and in the bulk of solution.HEYROVSKY,~ using oscillographic polarography, showed the reduction of tervalent bismuth to involve three-electron transfer, and to be irreversible in media containing undeformable anions such as NO,and ClO,-, but highly reversible in complex-forming media of C1-or Br-ions. These conclusions were confirmed by Randles and Somerton,2 who, investigating the electrodic behaviour in an alternating field, computed, as a measure of the degree of reversibility, the specific rate constant for the exchange Bi =+= Bi3+ + 3e.In N-perchloric and N-hydrochloric acid the constant was-reported as 3 x lo-* and 2 1 cm. sec.-l, respectively. The reversible behaviour on open circuit of both protected and unprotected bismuth electrodes as metal-metal oxychloride electrodes in hydrochloric acid media is undoubtedly consistent with the above facts. However, the extent to which anions such as NO3and SO:-may catalyse the above exchange does not seem to have been studied before. As is well known, these anions, like ClO,-, do not become specifically adsorbed. In this investigation, using a different experimental technique, we confirmed Randles and Somerton's results, and moreover examined the reactivity of the above anions, alone or in mixtures, towards electron transfer in the above reaction. EXPERIMENTALThe technique used was essentially polarography with superimposed alternating voltage.* The capacitative and resistive components of the impedance of a mercury surface were measured

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The dependence of the colour intensity of the iron(II1)thiocyanate complex formed a t two different ratios of thiocyanate to iron on the nature and concentration of the acid anion was studied. Four different acids were tested over the concentration range 0.05-1 .O N : perchloric acid, nitric acid, hydrochloric acid and sulphuric acid. Fading of the iron(II1)thiocyanate colour was ascribed to a specific effect of the anion caused by progressive masking of iron(II1) ions of the highly dissociated iron(II1)thiocyanate by the more strongly complexing anion ligand. The results were interpreted in the light of the calculated values of side-reaction coefficients between iron(II1) and the added ligand, as well as on the magnitude of conditional stability constants of iron(II1)thiocyanate in the various media. That the order of effectiveness of the added anions towards complexing iron(II1) ions is SO,2-> C1-> NO,-> C10,was further substantiated.

The extraction behavior of more than 60 chemical elements in the systems of 10 % Amberlite LA-1 xylene solution vs. hydrochloric acid and 5% tri-iso-octylamine xylene solution vs. hydrochloric acid is presented and discussed, the acidity being varied from 1 to 12M. The distribution ratio, Kd, of the particular nuclide was determined by the use of radioactive tracer. Although the shapes of the acid dependence curves for each element resemble each other in the two systems, yet the Kd values in the TIOA system are generally higher than those obtained in Amberlite LA-1. The same regularity is to be noticed for the relationship between the Kd values of the elements at a definite acidity and their respective atomic number, Z, in the two systems examined. By comparison with the TBP-HCI, or the anion exchange resin-HCI systems, it is to be found that amines give acid and Z dependence curves quite analogous to those of the two former systems. The higher Kd values for scandium and heavier rare earth elements in the TBP-HCI system are, however, a rare exception.

Differential capacities were measured in O.~N-NH,CI and -NH,F and in 1.0-, 0-3-, and O.~-N-HCI, in water and methanol. For the first two electrolytes, in both solvents, earlier results were conhned, and the method usually followed in interpreting the minimum capacity observed with increasing cathodic polarisation is discussed. In aqueous and methanolic hydrochloric acid solutions, reduction of hydrogen ions prevented extension of the measurements, and no capacity minima were observed within the cathodic potential range corresponding to ideal polarisation. The electrocapillary curves of mercury in the latter solutions were obtained. From the rate of change of the interfacial tension with the chemical potential of HCl, surface excesses of chloride ions were calculated for aqueous and methanolic 0.3~-hydrochloric acid, and the results compared.GRAHAME reported measurements of the differential capacity of the electrical double layer between mercury and methanolic salt solutions of ammonium chloride, fluoride, and nitrate. The outstanding features of the curves obtained for 0-1N-solutions are, first, the complete disappearance of the hump characteristic of the curves obtained in the corresponding aqueous solutions; secondly, the relatively low minimum capacity value, Cmin., of 9.0 pF/cm.2 observed on the cathodic potential side compared with that observed in aqueous solutions, viz. ,2 154--16.0 yF/cm.2. At potentials less cathodic than that corresponding to Cmin., the curves diverged because of the specific adsorption of anions (Cl-), but they coincided almost exactly at more cathodic potentials. Because of this similarity in behaviour, and by comparison with that observed in aqueous solutions, was considered to indicate complete repulsion of any specifically adsorbed charge from the metal surface. Grahame pointed out that conclusive evidence could be obtained from the rate of change of the differential capacity with chemical potential, but the necessary data, the activity coefficient values in methanol, are lacking. From surface-tension measurements in aqueous and methanolic hydrochloric acid solutions, Parsons and Devanathan had shown that anions are less readily repelled from a negatively charged mercury surface in methanol than in water. In methanol positive adsorption of the C1ions even at potentials corresponding to hydrogen evolution was reported, a result apparently not in accordance with Grahame's conclusion.We measured differential capacities in 0.1N-aqueous and -methanolic ammonium chloride and fluoride under conditions differing only in minor details from those used by