150 PHENOMENA, ATOMS, AND MOLECULES 



chemically activated and can, under proper conditions, retain its activity 

 several days. A very brief review of this evidence will be of interest. 



1. It has been shown ^ that when a wire of tungsten, platinum or 

 palladium is heated to a temperature above 1300° K. in hydrogen at very 

 low pressure (o.ooi to 0.020 mm.), the hydrogen slowly disappears. There 

 is a distinct fatigue effect, but the substitution of a new section of wire 

 does not restore the action. The hydrogen is not absorbed by the wire, but 

 is deposited on the glass, especially where this is cooled by lic[uid air. If 

 the cooled portions are heated, ordinary hydrogen is liberated which will 

 not recondense on replacing liquid air. The hydrogen may deposit on cooled 

 glass surface, even in tubing at a considerable distance from the bulb. 

 This hydrogen has remarkable chemical activity and will react with 

 oxygen and phosphorus at room temperature. These effects are not due to 

 the catalytic effect of finely divided metal deposits. The active hydrogen 

 is not affected by an electrostatic field and therefore does not consist of 

 hydrogen ions. 



2. The active hydrogen thus produced can diffuse through long tubes 

 (at low pressures) and can then dissolve in platinum (at 50°) and cause a 

 marked increase in its electrical resistance and corresponding decrease in 

 its temperature coefficient. Ordinary hydrogen, under similar conditions, 

 will not do this. These effects have been descril)ed in some detail by 

 Freeman. ^"^ 



3. It has been found that tungstic oxide, WO3, platinum oxide, Pt02/^ 

 and many other substances, placed in a bulb containing a tungsten filament 

 and hydrogen at very low pressures, rapidly become chemically reduced 

 when the filament is heated to a temperature exceeding about 1700° K. 

 although otherwise they are not acted on by hydrogen. 



Many of these phenomena have been studied quantitatively in some 

 detail, and the results seem consistently to be in accord with the theory 

 that a portion of the hydrogen which comes into contact with the hot wire 

 is dissociated into atoms. These, perhaps because of strong unsaturated 

 chemical affinity, tend to adhere to glass surfaces even at room temperature. 

 Some, however, leave the glass and wander further. Gradually the glass 

 surfaces become charged with hydrogen atoms to such an extent that anv 

 fresh atoms striking the surface, combine, even at liquid air temperatures, 

 with those already present. In case the atoms strike a metal surface such as 

 platinum, they dissolve in it up to a considerable concentration. 



^ "A Chemically Active Modification of Hydrogen," Langmuir, Jour. Anicr. Chcm. 

 Soc. ^4, 1310 (1912). 



'^'^ Jour. Amcr. Chcm. Soc, 33, 927 (1913). 



'^ Formed and deposited on the bulb by heating Pt at very high temperature in On 

 at low pressure or by passing a glow discharge between Pt electrodes in O2 at low 

 pressure. 



