Abstract :
A conventional form of oxide-cathode diode can, in appropriate circumstances, evolve a continuous current-dependent stream of electrolytic oxygen. This oxygen emerges from the cathode surface as a negative ion and passes to the anode, where it may or may not be chemically absorbed. If absorption is incomplete, a proportion of the oxygen can be returned to the cathode and give rise to a number of characteristic reactions. These reactions are studied and shown to be analogous to the electrolytic actions of the S-type assembly described in Part 2 of the paper.