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XV. Absorption of .Hydrogen by Elements in the Electric 

 Discharge Tube. By F. H. Newman, Ph.D., F. Inst. P., 

 A.P.C.S., Head of the Physics Department, University 

 College, Exeter *. 



1. Introduction. 



rjpHE phenomenon of the disappearance of gas in the 

 JL electric discharge-tube, and in the presence o£ incan- 

 descent filaments, has received much attention recently owing 

 to its importance in technical applications. Langmuir f has 

 shown that hydrogen disappears from a vacuum tube in 

 which a tungsten filament is heated above 1000° C. # This 

 fact has been utilized by him in the removal of the last traces 

 of gas in valves, and the effect has been termed a " cleaning 

 up " one. The pressures at which he w r orked were very low ; 

 for example, he found that the pressure in a tube was lowered 

 to 0*00002 mm. of Hg. Other gases, including nitrogen and 

 carbon monoxide, are removed in a similar manner, and 

 molybdenum, when incandescent, has the same effect as 

 tungsten. In all cases Langmuir found that the cooling of 

 part of the apparatus by means of an enclosure at liquid- 

 air temperature greatly accelerated the rate of disappearance 

 of the gases. In addition he noted an electro-chemical 

 " clean up," which occurred at much lower temperatures of 

 the filament, when potentials of over 40 volts were used 

 in a way that caused a perceptible discharge through the 

 gas. 



More recently Campbell, conducting work for the General 

 Electric Company J and using incandescent filament cathodes 

 in electric discharge-tubes, has made an exhaustive study of 

 the " clean up " effect, and has come to the conclusion that 

 there is much evidence for believing there exists an electrical 

 action which is quite independent of the thermal action, and, 

 providing the temperature of the filament is kept below that 

 at which the chemical " clean up " occurs, the effect appears 

 to be one dependent only on the electrical discharge. In the 

 case of the disappearance of carbon monoxide there is proof 

 of the conversion of this gas into carbon dioxide, and the 

 action takes place more rapidly when part of the apparatus 

 is cooled to liquid-air temperature. This has the effect of 

 removing the carbon dioxide by condensation as quickly 



* Communicated by the Author. 



t Am. Chem. Soc. Journ. vol. xxxvii. (1915). 



X Phil. Mag. vol. xl. (1920) ; vol. xli. (1921) & vol. xlii. (1921). 



