GB410706A - Improvements in vacuum tight enclosed carbon arc lamps - Google Patents

Abstract

410,706. Arc lamps. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London.-(Assignees of Patent-Treuhand Ges. fur Elektrische Gl³hlampen; 11, Ehrenbergstrasse, Berlin.) Dec. 18, 1933, No. 35612. Convention date, Dec. 27, 1932. [Class 39 (i).] In a vacuum-tight arc lamp of the type comprising carbon electrodes and having a filling containing mercury vapour derived from metal in the envelope, the filling contains pure oxygen or oxygen and a gas or gases containing oxygen, but no nitrogen. Preferably the additional filling consists of carbon monoxide or carbon dioxide. For an arc 10 cms. in length a pressure of 5 mm. to 50 m.m. when the lamp is cold is suitable. The electrodes are degassed by heating in an atmosphere of carbon tetrachloride at about 2,200‹ C. and converting them into graphite in hydrogen at about 3000‹ C. A higher luminous intensity may be obtained by adding 50 per cent of hydrogen to the filling. Instead of hydrogen, gases containing hydrogen, for instance compounds of hydrogen and carbon, hydrogen and oxygen, or hydrogen, carbon and oxygen, may be used.