In the present study, the familiar Langmuir adsorption isotherm is applied to the mixed adsorption of methylene blue in the presence of halide ion. The variation of methylene blue prewave height or AC peak height with halide ion concentration is treated statistically. It is concluded that the decrease in the DC prewave or in the corresponding AC peak height is caused by the mixed adsorption of halide ion. The relative temperature coefficient of AC perk height was found to be 1.04% deg-1 at 25°C in 0.4M KNO3 with acetate buffer solution (pH 4.7).
A new method of sweep polarography is described, where in effect the change of surface concen-tration of depolarizer is recorded against the applied potential (ΔC3-E curve). Use of analogue computer circuit has been proved to be satisfactory to the purpose.
The ion-pair association constants of acids were determined from potentiometrical data obtained with the platinized platinum hydrogen electrode and saturated zinc chloride-zinc amalgam reference electrode. The investigation was also made in order to evaluate the behavior of acids in ethylene-diamine and to determine the acidity relationship between ethylenediamine and water solvents. The following relationship has been determined empirically: Below (pKa)H2O=7.0, (pKa)en=3.9; Above (pKa)H2O=7.0, (pKa)en= {3.9+(pKa)H2O}-7.0