Electrolytic Capacity and Resistance of Pt-Rhodamine B-Pt Cell, as Determined by a Phase Angle Method of Measurement

Abstract

Direct measurement of the phase angle of any reactive circuit.-The circuit is placed between A and B in one arm of a bridge, an adjustable resistance R between B and C, two equal resistances between A and D and between D and C. An e.m.f. E is applied at A and C, and the potential difference between B and D is determined by applying a known e.m.f. in quadrature with JS, and adjusting for zero current. For highest sensitiveness, R should equal the impedance of the reactive circuit. The sensitiveness increases with decreasing frequency. The method is useful in testing any auto-transformer.Sensitive null instrument for alternating currents.-A direct current galvanometer was connected in series with a synchronous commutator, permitting independent adjustment of E and R for zero current.Electrolytic capacity and resistance of Pt-Rhodamine B-Pt cell-was measured by the phase angle method for various cells with electrodes of solid Pt or of cathodically deposited films of various thicknesses in various relative positions. The results can be regarded as correct only when the electrodes have relatively small resistance. For the case of two parallel plates, the correction for the resistances of the electrodes is made. Variations with e.m.f. and frequency. The resistance is constant but capacity increases with e.m.f. for values above 0.4 volts and decreases with frequency in proportion to l/v7 for 10 to 70 cycles. Variation with arrangement of electrodes. A cell with parallel solid electrodes has a greater capacity than one with the same electrodes lying in a plane. The capacity increased as the thickness of the sputtered film decreased and was greater for films with a black color. Effect of increasing concentration and temperature was to increase the capacity and decrease the resistance.