VISUAL OBSERVATION OF BUBBLES AT HORIZONTAL ELECTRODES AND RESISTANCEMEASUREMENTS ON VERTICAL ELECTRODES

A comparison was made of the bubbles formed on a horizontal bottom-fac ing electrode in a physical analogue model with. those formed electrol ytically, Bubbles formed in a physical analogue model by forcing air t hrough a porous plate are larger, with wetted clear areas between bubb les. In contrast, electrolytically generated gas bubbles are smaller a nd the electrode surface is covered with a foamy layer of tiny bubbles . To measure the bubble resistance on horizontal electrodes, a method was developed for vertical electrodes so that the measurements may be validated by comparison with published data. Voltage fluctuations were measured and analysed using fast Fourier transform (FFT). The magnitu de of the bubble impedance was obtained at a superimposed a.c. frequen cy f(0). The phase angle caused by the effects of the double layer cap acitance and the faradaic impedance on bubble resistance were determin ed. The effects of the faradaic impedance and the double layer capacit ance were shown to be negligibly small under experimental conditions.