BETWEEN THE CONDITIONS OE A. CHEMICAL CHANGE AND ITS AMOUNT, 131 
M 3 M 4 , and M 1 T 1? M 3 T 3 the times in which under these circumstances the reaction would 
complete itself. The results arrived at are (1) M 4 P 4 : M 2 P 2 : : M 3 P 3 : M 4 P 4 ; and conse- 
quently (2) P 2 Q 2 : M 4 P 4 : : P 4 Q 4 : M 3 P 3 , (3) P 2 ' Q 2 : M 4 P 4 : : P 4 ' Q 4 : M 3 P 3 , (4) M 4 T r 
=M 3 T 3 . If the interval M 4 M 2 be one minute and M 4 P 4 be the unit of potential 
change, then P 2 Q 2 represents a units of actual change. 
We have thus investigated the relation existing between the amount of chemical 
change and the amount of hydric peroxide, and have shown that the former of these 
quantities varies directly with the latter. We now proceed to inquire how the amount 
of change is affected by the variation of the other conditions of the reaction. 
For a particular system the amount of chemical change in a unit of time is expressed 
by ay, this expression representing the fact that if a is kept constant the amount of 
change varies directly with y, that is, with the amount of peroxide, and also that if y is 
kept constant it varies directly with «. That which has been kept constant in each set 
of experiments made to determine the values of y, and which is represented by a, is a 
group of other conditions upon which the amount of chemical change depends. The 
systems which have been made the subjects of experiment in this investigation have all 
been liquid homogeneous systems. And as the quantity of water used has been always 
very large in comparison with that of the various reagents, they may be further charac- 
terized as aqueous systems. 
Since these systems are homogeneous, they may conveniently be described by a state- 
ment of the ingredients of their unit of volume. We adopt, as before stated, the cubic 
centimetre for unit of volume, and shall use the units already defined (p. 128) in the 
measurement of the various substances. The whole amount of chemical change is a 
function of all the conditions of the system in which it occurs. If we call this amount 
X, the volume of the system, v, its temperature h, the time during which the change 
proceeds t, and the number of units H 2 0 2 , 11 1, ... A, B, C, . . . of the various ingre- 
dients in a unit of volume y, i, ... a, b, c , respectively, where A, JB, C are units of 
any substance which may be introduced into the system, then 
2 = f ( a , b, c, . . h, i, . . p, . . t, . . v . .). 
The form of this function is determinate in the case of two of these conditions, viz. t, v , 
and has been determined experimentally for this reaction in the case of p, so that the 
equation may be written in the form 
t=ptv .f{a, b, c, .. h, i. .). 
Now if we keep constant all the conditions in the undeterminate part of the function 
except one, say x, the form of the equation is 
%=ptv . <p(x), 
the constants in <p(x) being functions of the conditions of the system which do not vary. 
From this equation, knowing a series of values of X, p, t, v, x,< it is generally possible to 
determine the form of the unknown function. In each set of experiments made in the 
manner described, p and t vary while v and x remain constant, and the law of connexion 
