The Absorption of Gas in Vacuum Tubes

Abstract

This Paper is an account of experiments carried out to determine whether the absorption of gases caused by passing a discharge for some time through vacuum tubes is the result of a chemical action or is a mere physical absorption. In order to eliminate all electrode complications, the electrodeless discharge was used throughout. The bulbs examined were of soda, lead, Bohemia and Jena glass. The absorptions were noted at different pressures and curves plotted. Continued passage of a discharge causes a "saturation" effect in all the glasses. After two months none of the bulbs had recovered any of their absorptive power. If the action is chemical it is natural to expect various oxidation products to have been formed. Testing these bulbs with hydrogen we should expect a large initial absorption going to reduce these products. This was found to be the case for all the bulbs, the first reading for the soda glass giving 95 per cent. absorption of hydrogen. Having now reduced the oxidation products we should expect a reabsorption of oxygen under the discharge. This was also found to be the case. The series of readings show great regularity, the order of absorption for oxygen holding also for hydrogen. That chemical actions are present is shown by peculiar deposits on the necks of the bulbs, these being unfortunately too small for analysis. The inert gases show correspondingly small absorption, as shown by Soddy and Mackenzie, and therefore the conclusion is that the disappearance is not due to physical absorption, but to definite chemical action.