196 PHENOMENA, ATOMS, AND MOLECULES 



150000 calories. On the other hand, it should be emphasized that from 

 my experiments it is not possible to determine with certainty whether 

 or not hydrogen is dissociated at all. And — what is here very significant 

 — by the assumption of such a dissociation, the observed anomalies in 

 the heat losses do not find a sufficient explanation, for the anomalies also 

 occur even at temperatures as low as 2300-2400°, where surely. the 

 dissociation of hydrogen can play no part." 



Thus, according to Siegel, a dissociation as large as 11% at 2850° can 

 be reconciled with the e:jiplosion experiments. If we refer to Table XV 

 we see that we have found the dissociation at 2850° to be 9.2% at atmos- 

 pheric pressure. This should be ample to account for the anomalies found 

 by Siegel. 



Siegel's objection th^t the dissociation of hydrogen could not account 

 for the discrepancies observed at 2300-2400°, fails to apply to the present 

 results. Siegel does not state his reasons for believing that the heat of 

 dissociation is at least 150000 calories. Such a high value is at complete 

 variance with all the experiments described in the present paper. With 

 the value 84000 calories which we have adopted, the dissociation does not 

 fall off nearly so rapidly at lower temperatures. This is readily seen from 

 he following table: 



Siegel. Langmuir. 



q - 150000. g - 84000. 



T. X. AC/C. *. AC/C. 



2850 o.ii 13.0% 0.092 11.0% 



2300 0.0049 0.9% 0.014 2.6% 



The figures in the second column represent the degree of dissociation 

 calculated from Siegel's data, while those in the fourth column are taken 

 from Table XV. The third and fifth columns give the increase in the 

 "heat capacity of the system" HoO + MHo referred to by Siegel. Thus, 

 Siegel calculates that 11% dissociation at 2850° would increase the capacity 

 by 13%. The other figures were obtained from this by proportion, 

 taking into account, however, the effect of the temperature as was done in 

 the preparation of Table XIX. 



Thus, on Siegel's assumption of a high heat of dissociation, the effect 

 of the dissociation is to increase the heat capacity at 2850° by 13%, but 

 only by 0.9% at 2300°. It is evidently for this reason that he says that 

 "surely the dissociation can play no part" at such low temperatures as 

 2300°. . • . ■ 



Taking the values for the dissociation as calculated in the present paper, 

 we find that the heat capacity would be increased ii% at 2850 and 2.6% 



