xx DISSOCIATION 535 



of hydrogen and oxygen these two substances would func- 

 tion as " depolarising " electrodes for a trace of water 

 acting as electrolyte : 



2 H 2 + 2O|H 2 + O 2 

 giving 2H 2 O + 2H 2 O. 



Seventeen years before Baker's experiments were 

 carried to a successful conclusion, Armstrong acting on this 

 belief, ventured to affirm, " that some day it would be 

 ascertained that a mixture of pure oxygen with pure hydro- 

 gen was not explosive" (Proc. Chem. Soc., 1885, 1, 39). 

 He added, however, that " Water not being an electrolyte, . . . 

 it was difficult to understand that the presence of water pure 

 and simple should be of influence in the case of a mixture 

 of oxygen and hydrogen " (loc. tit. p. 40) ; to be effective 

 the water must be sufficiently impure to render it con- 

 ducting. 



The startling verification of these two daring predictions 

 by Baker's experiments in 1902 affords the strongest 

 evidence of the correctness of the views on which they were 

 based. 



SUMMARY AND SUPPLEMENT. 

 A. DISSOCIATION AND ASSOCIATION. 



Grove, in 1847, discovered that steam could be decomposed 

 by hot platinum, bubbles of detonating gas to the amount of 

 sj 1 ^ being formed when the steam condensed. The decomposi- 

 tion actually amounts to 



0-0078% at 1124 C. n8% at 1882 C. 

 0-0189% at 1207 177% at 1984 

 0-034% at 1288 



(Nernst, Wartenburg, Zeit. physikal. Chetn., 1906, 56, 533, 

 541). If the steam were cooled slowly, the hydrogen and 

 oxygen would recombine as shown by the lower arrow in the 

 equation 



