THE EFFECT UPON LIMITING CURRENTS AND POTENTIALS OF COUPLING A ROTATING-DISC AND CYLINDRICAL ELECTRODE WITH ULTRASOUND

The reduction of the silver cation, Ag+, was studied in dilute aqueous Na2S2O3/NaHSO3 solution at a platinum and stainless steel rotating el ectrode in the absence and presence of ultrasound. Under silent condit ions, electrode potential measurements indicate that silver deposition is the main reaction occurring at the cathode during the electrolysis of a model photographic processing solution. Under insonation conditi ons at 20 kHz the reduction wave shifts anodically with increasing ult rasonic power. Similarly the discharge of hydrogen shifted anodically with increasing power. It is also shown that below 1000 r.p.m. insonat ion leads to improved limiting currents when compared to the silent sy stem. As the rotation speed of the electrode increases above 1000 r.p. m., the limiting current decreases as the ultrasonic power increases. (C) 1997 Published by Elsevier Science Ltd.