406 



Mr. \Y. H. Pendlebury and Miss M. Seward. 



Table II. 



HC1 = 20 X 65-11 m.g.m. 

 HC10 3 = ux 61-3 m.g.m. 



Table III. 



HC1 = 15x65-11 m.g.m. 

 HC10 3 = ux 61-3 m.g.m. 



The connexion between the velocity of decomposition and the 

 amount of the decomposing substances present is of exactly the same 

 nature as that established in a similar way by Messrs. Harcourt and 

 Esson, viz., that the velocity varies in the first place directly with 

 the mass of the substance present, and that in the second place the 

 presence of the substance causes a slight acceleration in the rate 

 irrespective of its being decomposed. It has already been con- 

 clusively shown by their work and that of other experimenters on the 

 same lines that the presence in the liquid of any substance which, 

 as far as is known, has no chemical action upon the essential in- 

 gredients, and may therefore be considered to remain inactive 

 during the change nevertheless has its specific effect, accelerating or 

 retarding upon the velocity of the change. But Harcourt and Esson 

 pointed out that the decomposing substance itself likewise exercised 

 this secondary influence. It does so in this case, and the second 

 term in the empirical formula represents this secondary effect. 



