Katharine B. Blodgett

Cleanup of Atomic Hydrogen

When hydrogen is dissociated by an incandescent tungsten filament in a glass tube, some of it is cleaned up if the tube is cooled in liquid air. The amount cleaned up can be greatly increased by coating the inner wall with mercury or copper. In one experiment the amount cleaned up in cold mercury was equivalent to 14 monolayers of atomic hydrogen. The cleanup proceeded at a diminishing rate until the pressure fell to the value at which hydrogen left the mercury as fast as it entered. When hydrogen was cleaned up in a very thin coating of mercury there were 1.5 to 1.8 atoms of mercury per atom of hydrogen. All the cleaned‐up gas was recovered when the tube was brought to room temperature. After cleanup in copper there was little recovery until the temperature rose above —150°K.

THE EFFECT OF END LOSSES ON THE CHARACTERISTICS OF FILAMENTS OF TUNGSTEN AND OTHER MATERIALS

ABSTRACT The leads of a tungsten filament in vacuum cool the ends of the filament and so affect the voltage, candle power, electron emission and other properties of the filament. For long filaments, where there is a central portion at a uniform temperature Tm, the temperature distribution near the lead is derived. A method for determining T0, the temperature of the lead-filament junction, is given. Tables and formulas are presented which allow ready calculation of the effect of the leads on the properties of any long tungsten filament for which the current and diameter are known. From the more general results it has been found that the decrease in voltage due to the cooling of one lead may be represented by δV = 0.154 (Tm/1000)–0.081 (T0/1000)–2.1.10-8 T0Tm–0.056. There is an extension of the theory to cover the cases of filaments in gases, filaments of other materials, etc. Part II of the paper gives figures from which may be found the properties of filaments so short that the first theory does not apply. Some experimental checks of the theory are given. In general the results and the methods of application have been placed first, and the mathematical derivations have been placed at the end of each part. For a short filament with leads cooled in liquid air a negative slope of the volt-ampere characteristic when the central temperature is much smaller than Tm is observed.