GB190517933A - A New Method of Producing Vacua - Google Patents

Abstract

17,933. Soddy, F. Sept. 5. Exhausting.-To obtain a high vacuum in an electric lamp bulb, X- ray bulb, or other vessel, the air, either previously to or during preliminary exhaustion, is displaced by a gas wbich is afterwards absorbed by heated calcium or an alloy of calcium with magnesium or other metal; such gases include oxygen, hydrogen, carbon dioxide, carbon monoxide, water vapour, acetylene, ammonia, sulphur dioxide, and coal-gas. During the absorption, the vessel is-subjected to the same conditions of temperature as would occur in after use, thereby facilitating the complete absorption of occluded gases. In the form shown, the bulb A is first exhausted by means connected to the tube E, then supplied with oxygen, say, from a gas generator D, and again exhausted before the residual gas is absorbed by volatilizing calcium contained in an electrically-heated vessel C. Commercial calcium when heated in a vacuum gives off gases which are afterwards reabsorbed at a higher temperature, and such gases may be employed instead of gas from the generator D. A spectrum tube H is provided for determining by spectroscopic analysis the nature of the residual gases during exhaustion. Towards the end of the absorption, the temperature of the calcium is reduced to facilitate the absorption of dissociated hydrocarbons which may be present.