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The activity coefficients of NaBr and CaBr2 in NaBr-CaBr2 aqueous mixtures have been measured at 25 °C over the range of ionic strengths 0.1 to 7.5 m. The measurements were made with a dual electrometer amplifier using Na and Ca ion selective electrodes against a Br ion selective electrode. The data were fitted to Harned's equation of the form log y¡ = log y°-aAByB -|8ARyB2 to compute the trace activity coefficients and were also analyzed by using the Pitzer formalism. Deviations from the Pitzer formalism were observed for the experimental activity coefficients in this mixture.

The electrocatalytic activity of Ag-doped lanthanum chromites electrode materials viz., LaCr 0.4 Ag 0.6 O 3 and LaCr 0.7 Ag 0.3 O 3 prepared by decomposing the precursor complex is studied. Pure LaCrO 3 is synthesized by combustion route using oxalic acid as a fuel. The decomposition behaviour of the assynthesized powder obtained in the latter method is characterized by TGA-DTA and XRD. Both the precursor complex and the as-synthesized powder are calcined at 900 • C for 7 and 10 h, respectively. XRD of the final product after calcinations indicated the formation of perovskite phase with minor amounts of impurity phases of component oxides in the Ag-doped lanthanum chromites and pure perovskite phase in the undoped one. The surface morphology of the perovskites is studied by SEM. The electrocatalytic activity of the perovskite powders for borohydride oxidation is studied by using cyclic voltammetry (CV) at a catalyst loading of 0.7 mgcm −2 for both Ag-doped and undoped LaCrO 3 coated on glassy carbon substrate. Calibration plots are obtained by plotting the anodic peak current versus concentration of borohydride in the range of 20-100 mM. The sensitivities of the three perovskites towards borohydride oxidation indicated that LaCr 0.4 Ag 0.6 O 3 is the best among all the perovskites studied giving a value of 1.395 µA/mM.

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