An Investigation of a Case of gradual Chemical Change. 407 



Variation in Hydrogen Chloride. 



Having satisfactorily established the relation of the rate of change 

 to the amount of one of the reacting substances, namely, hydrogen 

 chlorate, we naturally sought to find the connexion between the 

 rate and the amount of hydrogen chloride the other reacting sub- 

 stance. It might be expected that the effect of variation in the 

 hydrogen chloride would result in equations of the same form as 

 those given above. Various series of observations were made to in- 

 vestigate this point. The amount of acid was varied in arithmetical 

 progression, and the rates obtained were divided by the quantity of 

 acid present in each case to see if anything approaching an arithme- 

 tical progression could be obtained. 



No such relation appears to exist, as is shown by the following 

 example : 



Table IY. 



HC1 = vX 65'11 3x51*5 millionth-gram-molecules per c.c. 

 HC10 8 = 3x51-5 



The first four or five numbers in the third column might perhaps 

 be brought into an arithmetical progression without any serious 

 alteration, but taken as a whole, the series of experimental results 

 cannot be thus interpreted. It appears then that tjie effect of hydro- 

 chloric acid is not, like that of chloric acid, of two kinds, viz., (1) a 

 primary one due to its being a decomposing substance, and (2) a 

 secondary one of the nature above described. Yet it can hardly be 

 supposed that it acts merely in a secondary way as a substance 

 present and not decomposed, for its effect is proportionally much 

 greater than that of chloric acid itself. Thus in the above series 

 when the quantity of acid is only a little more than doubled* (v = 10 



