GB387979A - Improvements in luminous electric discharge tubes - Google Patents

Abstract

387,979. Discharge lamps. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London.-(Assignees of Patent- Treuhand Ges. fur Elektrische Gl³hlampen; 11, Ehrenbergstrasse, Berlin.) Oct. 25, 1932, No. 29861. Convention date, Dec. 17, 1931. [Class 39 (i).] The envelope of a lamp having a filling including one or more vapours of difficultly vaporizable metals and a rare gas or gas mixture consists of a double wall, the inner space of which contains the electrodes and the difficultly vaporizable metals the vapour pressure of which during operation is not in excess of 1 mm. while both spaces, which are in communication, contain the rare gas filling. It is stated that during operation the metal vapours remain in the inner space, particularly when the communicating passages are small apertures or slits, formed, for example, by leaving a space where the electrode leads pass through the inner envelope. Suitable metal vapours are' thallium, magnesium, zinc, cadmium, calcium, gallium, indium, bismuth, or antimony. Mercury or a mercury amalgam, at a pressure in excess of 1 mm., may be added. Thallium at a tube temperature of 600‹ C. emits a green light, zinc at 400‹ C. a blue, and magnesium at 400‹ C. a yellow-green. A combination of zinc and mercury, or thallium and mercury emits a light approximating to daylight, that given by the thallium-mercury combination being strongly actinic. The combination of magnesium and mercury yields a powerful ultraviolet light source.