On a new kind of glow from palladium in vacuum tubes

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The phenomenon described in this paper was first noticed when making some preliminary experiments in an investigation suggested by Prof. Sir J. J. Thomson. The effect of the gases contained in metals on the nature of the discharge obtained when these metals are employed as electrodes in vacuum tubes has long been a question of interest. It was suggested that by employing palladium one might hope to obtain interesting results, owing to the property possessed by this metal of absorbing large quantities of hydrogen. The result of these preliminary experiments has already been briefly stated, but as the effect seems to be a new one, it seemed of sufficient interest to call for a fuller investigation. Apparatus .—A tube was fitted up containing an ebonite plug through which two stout brass leads were passed. To the extremities of the leads was attached, by means of screws, a piece of palladium foil about an inch in length and a tenth of an inch wide. The leads and plugs were fixed in position by sealing-wax. The tube was sealed by the blow-pipe to a mercury pump and was in connection with a pressure gauge, drying-bulb, etc. The tube could be isolated from the rest of the apparatus by means of a barometric mercury seal. By passing an electric current through the palladium, it could be heated to any required temperature.