90 
Proceedings of Boyal Society of Edinburgh. [sess. 
in a similar manner and taken into account in determining the 
rate of increase. The figures obtained are given in the following 
table ; in the case of solutions Y. and VI., A indicates the initial 
figure. 
Acidity , in c.c. of Y/5 alkali required to neutralise 5 c.c. of 
the solution. 
Time in 
days. 
Sol. I. 
Sol. II. 
Sol. III. 
Sol. IY. 
Sol. Y. 
Sol. YI. 
0 
A 
A 
1 
2*63 
2-09 
2-21 
2-20 
A + 2-74 
A + 2-66 
2 
4-86 
3*98 
4*01 
4-11 
4*90 
4*79 
3 
6-61 
5*58 
5-68 
5-77 
671 
6- 77 
4 
8-24 
6-89 
7*19 
7-17 
8-38 
8-30 
5 
9*54 
8-18 
8-40 
8-42 
9-63 
9*37 
6 
10*56 
9-25 
9-29 
9-46 
10-60 
10-34 
7 
11-43 
10-14 
10-22 
10-40 
11-37 
11-29 
8 
12-11 
10-94 
11-10 
11-21 
12-05 
12-03 
9 
12-65 
11-53 
11-67 
11-80 
12-53 
12*53 
10 
13-17 
12-10 
12-23 
12-33 
12-90 
12-94 
00 
15*34 
15-34 
15-32 
15-31 
14-56 
14-82 
These figures show that the addition of a neutral salt simply 
retards the action somewhat, hut the end point is the same as with 
persulphate alone. In solutions III. and IY. the h T H 4 ' concentra- 
tion is doubled, or nearly so, and yet the velocity is not increased ; 
hence equation b cannot determine the reaction-velocity. This 
must therefore he determined by equation a, that is, by the action 
of Ag* on S 2 0 8 ", as already deduced on other grounds. The 
retardation caused by the addition of the various salts would thus 
be explained, for such an addition would tend to diminish the 
concentration of the persulphate ions. 
The effect of acids, as shown in Y. and YI., is specially note- 
worthy. At first it would appear that the action is accelerated ; 
but the end point is not the same as in the other case, indicating 
the simultaneous occurrence of some other action which results in 
the production of less acid. The equation 
(e) 2 Ag 2 0 2 + 4H‘ = 4Ag* + 0 2 + 2H 2 0 
would represent such an action, and it is evident that in this case 
an increase of acid concentration would tend to accelerate the 
change. 
