BETWEEN THE CONDITIONS OE A CHEMICAL CHANGE AND ITS AMOUNT. 133 
of which the amount of actual change that would occur in a minute, the system con- 
taining constantly a unit of potential change, is determined by several experiments. 
The degree of coincidence of these experiments in each set may be observed by com- 
paring the values of this amount calculated from the successive intervals on the hypo- 
thesis already established, that the actual change at any moment is proportional to the 
potential. The number of units of potential change at the commencement of a set of 
experiments is denoted by p 0 , and the number of units of actual change occurring in each 
experiment is denoted by a. 
The volume of the solutions employed was 993 cubic centimetres, and their tempe- 
rature 30° C. The actual weights of the substances taken were, in each set, 
Hydric sulphate, 37T grms., 
Sodic peroxide, '0174 grm., 
Sodic hyposulphite (one measure), ‘0217 grm. ; 
in successive sets, 
Potassic iodide, •6. '9, T2, T5, l‘8grm. 
The weights of sodic peroxide and sodic hyposulphite are so small in comparison with 
that of the hydric sulphate, that the amount of acid neutralized by these salts is insigni- 
ficant. The formation of a correspondingly small quantity of .sodic sulphate may also 
be disregarded; for a separate experiment made with a large quantity of this salt 
proved that its influence upon the rate of change is very slight. But the potassic iodide 
was used in rather larger proportion ; and it seems probable that some double decompo- 
sition occurs between it and the hydric sulphate. 
Hence the permanent ingredients of a unit of volume of the system in each set of 
experiments were 
(381-3— 1-82 z)H 2 S 0 4 , 1-82 {(n-z) KI+z HI}, 1-82 zKHSO,, 
w(T82 KI) being the weight of potassic iodide taken for every cubic centimetre of the 
several solutions, and z being the fraction of this iodide decomposed by the hydric 
sulphate. 
Table V. 
Po = 
a = ' 
044.’ 
p»- 
3. 
044! 
Po = 
4. 
•044! 
Po = 
■044! 
n =1 
jPo~ 
6. 
• 226 . 
■044. 
Intervals. 
«■ 
Intervals. 
1 « 
1 
Intervals. 
Intervals. 
«• 
Intervals. 
*■ 
7-33 
•0302 
4-78 
•0457 
3-65 
•0604 
2-87 
•0757 
2-35 
•0923 
9-4 
•0302 
6-14 
•0455 
4-73 
•0600 
3*68 
•0755 
3-10 
•0895 
35-47 
•0301 
8-61 
•0452 
6-59 
•0604 
5-12 
•0757 
4-25 
•0906 
103-63 
•0303 
14-39 
•0449 
11-16 
•0601 
8'55 
•0748 
7*05 
•0900 
53-26 
•0451 
52-20 
•0601 
29-78 
•0762 
23-97 
•0902 
The values obtained for a from the different experiments of each set are fairly con- 
cordant, and we may therefore assume their mean to be the true value. It is at once 
evident that these numbers are in arithmetical progression, and bear to one another the 
same ratios as the values of n, viz., 2 : 3 : 4 : 5 : 6. They are compared below with a 
series of numbers calculated on this hypothesis. 
MDCCCLXVII. t 
