GB217646A - Improvements relating to thermionic valves or electron discharge tubes particularly for wireless signalling - Google Patents

Abstract

217,646. Levy, L. A. March 19, 1923. Thorium and alloys, depositing.-A tungsten, platinum, or other filament for use in a thermionic valve is treated in an electrolyte containing a solution of a thorium compound. The electrolyte may consist of 10 grms. of hydrated thorium chloride and 10 grms. of sodium chloride dissolved in 50 c.cms. of water and 50 c.cms. of alcohol. Tungsten wire is connected as cathode and is passed at such a rate that each part of the wire remains in the electrolyte for not more than half a minute so as to avoid the deposition of thorium oxide. The current density may be adjusted to 2 amps. per square inch by the use of an auxiliary cathode. In a modified process a small amount of a salt of nickel, copper, lead, or other metal, for instance 2 grms. of nickel per litre, may be added to the electrolyte. It is suggested that nickel is deposited either in metallic form or as a compound which occludes or assists in depositing thorium. Thorium per-. chlorate produced by saturating perchloric acid with thorium hydroxide may be used instead of thorium chloride. In another method, thorium is deposited on metals of the platinum group from an electrolyte consisting of a solution of anhydrous thorium chloride in a mixture of fused sodium and potassium chlorides.