BETWEEN THE CONDITIONS OE A CHEMICAL CHANGE AND ITS AMOUNT. 137 
proportionality in the case of the reaction of hyclric oxalate and permanganate. The 
measurements are no longer of the course of a single gradual action. The several series 
might be represented by equations expressing such a complication as it is most likely 
occurs, e. g., the gradual oxidation of potassic iodide to iodate, and the gradual reduction 
of this salt by hydric iodide. But the constants of such equations cannot be determined 
from the experimental numbers with sufficient accuracy for much reliance to be placed 
upon them. 
In consequence therefore of these two facts, — that the amount of change is a function 
both of the kind and of the amount of acid in the solution, and that the nature of the 
reaction is changed when a mixture of hydric and potassic iodide is used, — we have only 
been able to investigate the relation which exists between the amount of iodide in the 
solution and the amount of change in a particular case, namely, when the solution 
contains a sufficient quantity of free acid to render immaterial the replacement of a little 
of it by hydric iodide, and to determine sharply the occurrence of the single reaction, 
H 2 0 2 +2HI=2H 2 0+ 1 2 . With this limitation, the form of the function <p(i) in the 
expression IL—ptv . <p(i) has been established by the foregoing experiments, and we may 
now write the general equation in the form 
2=i])tv.f(a, b, c , . . .). 
That is to say, the amount of change varies directly, (1) with the amount of iodide, and 
(2) with the amount of peroxide in a unit volume of the solution; (3) with the time 
during which the change proceeds ; (4) with the total volume of the solution ; and, 
finally, with some function of each of the other conditions under which the change occurs. 
