130 MESSES. A. Y. HAKCOTJET AND W. ESSON ON THE LAWS OE CONNEXION 
change may be represented by H 2 0 2 -f2HI, and the unit of potential change by 
I. Employing this notation, the result stated above maybe expressed by 
saying that when there exists in a system a constant quantity, 
p(S 2 0 2 +2HI), 
uy(H,_0 2 +2HI=2H 2 0+I 2 ) 
occurs in one minute. For example, in the sets of experiments recorded in Table IV., 
the following values were found for a, *0242, ‘085, ‘0043, -0949, '0268, T31. These 
numbers represent the fractions of a unit of actual change that would occur in one 
minute, if there existed throughout that time in each system a unit of potential change. 
The difference between the values of a depends, it is plain, upon the different conditions 
of these sets of experiments which are contrasted at the heads of the several columns. 
The relation between the potential change in the system and the actual change 
occurring at a particular time may also be represented by supposing the rate, which up 
to that time has continually decreased, to become thenceforward uniform. Then the 
whole potential change being y , ay becomes actual in each successive minute, and the 
whole will have become actual, i. e. the reaction will have come to an end, in - minutes. 
Whence it appears that if it were possible actually to make the rate uniform, as may 
approximately be done by continually raising the temperature of the solution, or other- 
wise compensating the diminution of peroxide, the time required for the completion of 
the reaction would be independent of the time at which the rate was thus modified, that 
is, of the amount of potential change existing in the system. For example, in the last 
set of experiments given in Table IV., if at any moment whatever while the reaction was 
proceeding the rate of change could have been made constant, in (rffrx— ) 7’6 minutes 
from that time the whole change would have been accomplished. Whatever amount 
of peroxide the solution contained, this would equally have been the case ; in 7 - 6 minutes 
the whole of the peroxide would have disappeared. * 
These results may be illustrated graphically by the following figure. 
The curve P 4 P 2 P 4 represents the course of 
the reaction as determined by a set of experi- 
ments. Mj M 2 , M 3 M 4 represent any two equal 
intervals of time; M 4 P 1? M 2 P 2 the potential 
changes at the beginning and end of M 4 M 2 ; 
M 3 P 3 , M 4 P 4 the potential changes at the begin- 
ning and end of M 3 M 4 ; P 2 Q 2 , P 4 Q 4 the actual 
changes that have occurred during these inter- 
vals ; P 4 T 1? P 3 T 3 , tangents to the curve at P 4 , P 3 , 
represent the course of the reaction if it were to 
maintain the same rates with which it was pro- 
ceeding at Pj, P 3 respectively; P 2 Q 2 , P 4 ' Q 4 the 
actual changes which would occur with these uniform rates during the intervals M 4 M 2 , 
