Thorn Electrical Industries Limited

David O Wharmby

Alan G Chalmers

Frank L Whittaker

Electrical discharge lamps containing mixed halides of superior performance are provided by the inclusion in the lamp of a volatile complex halide compound of tin and sodium. The halide may be added as a mixture of tin and sodium halide but the complex is formed in operation of the lamp and has a much higher volatility than the constituent halides. The preferred lamps contain 5 to 100 micromoles tin and 1 to 250 micromoles sodium halide per cubic centimeter, in a gas fill containing more than 50 micromoles per c.c. mercury.

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London, United Kingdom

David O Wharmby