Differential electrolytic potentiometry with periodic polarisation. Part XXI. Introduction and instrumentation

Abstract

Previous work on periodic polarisation of indicator electrodes is reviewed and discussed, and is faulted on the premise that perfectly symmetrical, bias-free waveforms may not have been used. A statement of intent of the present work is made. The fabrication, activation and testing of electrodes is described, waveform generators are critically discussed, and measuring instruments for periodic and d.c. potentials are both described and evaluated. A simple device for interfacing instruments to recorders, offering a high degree of band spread, is described. High-voltage square-wave generation by use of relays is also discussed. Waveform monitoring was a crucial factor in the work, and the accurate balancing of shape, amplitude and half-cycle duration is described. Frequency measurement and timing by means of a crystal clock, and amplitude and bias detection by integration and by d.c. differential electrolytic potentiometry, are appraised. Finally, the working assembly is described, together with the technique for the elimination of electrical interference.