GB208694A - Improvements in the preparation of electric discharge devices - Google Patents

Abstract

208,694. British Thomson-Houston Co., Ltd., (Assignees of Charlton, E. E.). Dec. 21, 1922, [Convention date]. Distilling alkali metals. -Alkali metal such as caesium or rubidium, introduced into an electric discharge tube by placing in a chamber communicating with the tube a mixture of a compound of the alkali metal with an excess of a reducing agent, exhausting the tube and chamber, and heating the mixture. A tube 1 for use as a lamp is provided with a side tube 9 having distillation bulbs 11. The tubes are heated to 450‹ C. during exhaustion, and water vapour is removed by means of a liquid-air trap between the exhaust connection 12 and the pump. The tube 9 is opened and a mixture of caesium chloride, with a reducing agent, such as calcium or magnesium, preferably in the form of fine turnings, is admitted. The tubes are heated again to 250‹ C. while on the pump. Heat is applied to the tube 9 and caesium produced by the reaction is distilled successivelv into the bulbs 11 and into the tube 1. The tube 9 may be sealed off or may remain in permanent connection with the tube 1. Specification 184,446, [Class 39 (i), Electric lamps, Arc &c.], is referred to. The Specification as open to inspection under Sect. 91 (3) (a) comprises also the following methods of introducing alkali metal. Caesium or other alkali metal is introduced into the exhausted bulb of a thermionic valve, by applying to the anode, or to another part operating at a high temperature, a mixture of a halogen compound of an alkali metal with an alkaline earth metal and a binder such as a cellulose solution in amyl acetate. Alkali metal is evolved by heating the anode by means of a discharge or by a passage of current. In another method the mixture is applied to one or both of two disc electrodes which are heated by high frequency currents induced by a winding outside the bulb. This subject-matter does not appear in the Specification as accepted.