Conditions of Chemical Change. 179 



perties ; whereas we can identify, by suitable mechanical 

 means, in vaporized sal ammoniac the real gases ammonia and 

 hydrochloric acid. Yet, forsooth, there may be a relation 

 between these two phenomena, and we teach boys in our 

 public schools that chemistry is an exact science ! But apart 

 from these arguments, which are based upon the nature of 

 the evidence of the phenomena in themselves, without con- 

 sidering others which may or may not be logically deduced 

 from them, there is further the dilemma, poinded out alike by 

 Armstrong * and Pickering f , that those compounds which we 

 regard as most undecomposable are precisely those which 

 electrolytically most decompose, and this, too, as an effect of 

 solution in water, generally considered a relatively inert 

 material. 



Here, again, Prof. Ostwald would seek to draw us into 

 a side-issue by the supposition that his opponents would 

 confound stability with reactivity. The stability of a com- 

 pound is generally represented as an attribute of it with 

 reference to the decompositions produced by forces other 

 than chemical ; its reactivity is an attribute of it with 

 reference to those forces which we call chemical. Yet the 

 reactivity of substances is considered to be a function of their 

 electrolytic dissociation, or their instability when dissolved in 

 water. 



Again, the argument brought forward by Pickering % 

 seems as yet to have been unanswered and to be well-nigh, 

 unanswerable, namely, that if we acknowledge the doctrine of 

 electrolytic dissociation we must deny the principle of the 

 conservation of energy, for which there is an abundance 

 of direct evidence. This writer has pointed out, as one 

 example out of many, that if two molecular proportions of 

 hydrochloric acid, when dissolved in water, be entirely disso- 

 ciated into their individual atoms, there must be an absorption 

 of 44,000 -\-x-\-y cals., whereas, as a matter of fact, there is an 

 evolution of 34,630 cals., or a creation of an amount of energy 

 represented by (78,630 -\-x + y) cals. out of nothing and from 

 nowhere. 



In fact many writers of the present day seem to deal with 

 electric and chemical forces or electrified and non-electrified 

 atoms as two cards in a kind of game of blind-hookey, either of 

 which may be turned up at will. 



But there is the real dilemma of the reactivity of substances 



* l Electrician/ August 26th, 1887. 

 t Phil. Mag. [5] xxix. p. 425. 

 % Cf. supra. 



