210 SCIENCE PROGRESS 



derived? Ostwald (B.A. Report, Leeds, 1890, p. 333) suggested 

 that— 



" the ions H and CI are allotropic forms of the elements, similar 

 to red and yellow phosphorus, and contain very different 

 amounts of energy from those which they contain in their 

 common state of hydrogen and chlorine gases." 



Arrhenius (loc. cit. 1889) expressed the same idea by quoting 

 the case of oxygen and ozone as justifying the positive values 

 which he had found for the heat liberated in electrolytic dis- 

 sociation. 



" One case of ordinary dissociation is known in which the 

 decomposition is accompanied by liberation of heat. If two 

 gram-molecules of ozone (0 3 ) are converted into three gram- 

 molecules of Oxygen (0 2 ) the change is accompanied by the 

 development of not less than 30,000 calories." 



But these analogies are rendered altogether invalid if the 

 ions in question are merely single atoms electrically charged. 

 The energy of an atom may be decreased by combination with 

 other atoms, but an increase of energy would only be possible 

 if the atoms were to exert an actual repulsion against which 

 work could be done — a possibility that is altogether foreign 

 to present-day chemical conceptions. Whilst, therefore, the 

 conversion of one complex into another may be accompanied 

 either by an absorption or by a liberation of energy, the dis- 

 sociation of a molecule into single atoms must inevitably be 

 endothermic. 1 The hydrogen or chlorine ions cannot, therefore, 

 owe their superior stability to allotropy, if that somewhat 

 vague term is interpreted as referring to differences of mole- 

 cular structure such as those which exist in red and yellow 

 phosphorus or in oxygen and ozone. 



If then the ions exist in solution as single charged atoms they 



1 " If anything at all is certain about atoms, it is that the atoms in an ele- 

 mentary molecule are united very firmly together, and that therefore in separating 

 them a very large absorption of heat would occur. To separate 2HCI into 2H 

 and 2CI would absorb far more heat than the 2 x 22,000 cal. which we know are 

 absorbed in separating 2HCI into H 2 and CL. Yet the supporters of the dis- 

 sociation theory would have us believe that this separation has actually taken 

 place, not only without any absorption of heat, but actually with a development 

 of 2 x 17,300 cal. ; that is, that 2 x 22,000 + 2 x 17,300 + x cal. have been 

 created, and that, too, through the intervention of the water, which has ex 

 hypothesi no action whatever" (Pickering, "On the Theory of Solution," B.A. 

 Report, Leeds, 1890, p. 319). 



