An Investigation of a Case of gradual Chemical Change. 409 



rapidly. Now if two reactions of the nature above described are 

 really taking place, it would lead us to conjecture a connexion 

 expressed by the following equation : 



R = ku(l+au + fiv) + k'uv(l + <x,'u + l3'v), 



u and v representing as usual the quantities of hydrogen chlorate and 

 hydrogen chloride present, the other letters constants. 

 This expression is of the form 



when v is the only variable, and a series of such rates for which v 

 was varied in arithmetical progression would have its second 

 differences constant. Possibly the coefficient |8 is negative, i.e., the 

 presence of hydrogen chloride interferes with and retards the decom- 

 position of hydrogen chlorate by itself. This would explain why, in 

 the rates obtained with larger quantities of hydrogen chloride (v = 17 

 to v = 20), the ordinary formula 



more nearly expresses the results obtained ; the reason of this being 

 that in the presence of a large quantity of this acid the other reaction 

 may be altogether stopped. All this, however, is conjectural. A 

 second series obtained could not be brought into partial agreement 

 with the formula above ; yet other mixtures of potassium chlorate 

 and hydrogen chloride gave series of numbers of exactly the same 

 character as this first one. These series we shall give later. The 

 variation of the rate with the amount of hydrogen chloride present is 

 evidently by no means a simple one. The interpretation of its com- 

 plications that we have suggested can scarcely be considered fully 

 established. It would, however, account for the facts observed. 



Since in the main reaction which we desired to study, viz., that 

 between potassium chlorate and hydrogen chloride, there would be 

 produced during the reaction some amount of potassium chloride by 

 the decomposition of the chlorate, we determined the effect of the 

 addition of potassium chloride to the mixture of the two acids, 

 hydrogen chlorate and chloride. 



We have already referred to the fact that in gradual reactions, such 

 as the present, substances which remain in the solution apparently 

 unchanged throughout the whole reaction yet exercise their specific 

 influence, accelerating or retarding, on the velocity of the change, 

 hence it becomes important to ascertain the effect of the potassium 

 chloride. When the potassium chlorate and hydrogen chloride are 

 mixed together, the latter being always in some excess, there is 

 double decomposition, and potassium chloride and hydrogen chlorate 



