HYDROGEN INTO ATOMS 149 



remove the discrepancy between the previous calculations and Bjerrum's 

 results. 



QUALITATIVE EVIDENCE FOR THE DISSOCIATION OF H2 



H. von Wartenberg,^ after pointing out the discrepancy between the 

 former calculations and the results of the explosion method criticises the 

 heat conductivity method as follows : 



"Die Fehlerquellen der Methode sind zu gross, als dass man die Zahlen 

 auch nur als annahernd richtig betrachten konnte, wenn auch eine geringe 

 Dissociation des H2 von etwa 2100° nicht als ausgeschlossen erscheint. 

 Sichere Zahlen wird wohl nur die Explosionsmethode geben konnen." 



As far as accurate quantitative determinations of the degree of dis- 

 sociation of most complex gases are concerned, we feel that von Warten- 

 berg's preference for the explosion method is justified, but for qualitative 

 evidence of dissociation, especially of elementary gases, we consider that 

 the heat conductivity method has great advantages over the explosion 

 method. The fact that mixtures of gases must be employed in the latter 

 method, so complicates the phenomena that there is considerable un- 

 certainty in the interpretation of results. Furthermore, it will be shown 

 that the conductivity method, in some cases, is very much more sensitive 

 that the explosion method. 



The qualitative evidence of dissociation of hydrogen obtained by the 

 heat conduction method and already published, may be briefly summarized 

 as follows : 



1. The heat loss from tungsten wires (or platinum wires up to 1750°) 

 in nitrogen, mercury vapor, argon, and carbon monoxide varies with the 

 temperature accurately, as expressed by equation (2). 



2. The heat loss in hydrogen follows accurately the same law up to 

 about 1900° K. and then rapidly increases, until at 3500° K. it is over four 

 times its calculated value. 



3. No secondary electrical effects which might cause a similar in- 

 crease can be detected. 



4. At lower pressures the heat loss from tungsten wires in hydrogen 

 becomes actually greater than at atmospheric pressure. This does not occur 

 with other gases. 



The evidence of dissociation is, however, not at all limited to the ab- 

 normal heat conductivity, 



A large amount of evidence of a chemical nature has gradually ac- 

 cumulated in this laboratory, which proves, beyond doubt, that hydrogen 

 at low pressures, upon coming in contact with a heated metallic wire, is 



^ Z. Elektrochem., ig, 901 (1913). 



