The paper is divided into three main sections. The first of these deals with the method of manufacture and formation of the discs, and with the forward and reverse voltage/current and voltage/resistance characteristics and the effects of temperature variations, ageing and capacitance. This section includes a brief account of a theory of the operation of the rectifier.The second section describes the design of actual rectifiers for resistive or inductive loads and also a new method of design for battery-charging rectifiers, the mathematical theory of which is given in an appendix. A new method of construction is described which enables the output of a rectifier to be increased.In the final section, a description is given of some of the applications of the rectifier, including the use of oil-cooling for large outputs.