AT THE MOMENT OF CHEMICAL CHANGE. 
797 
These two experiments were made in the small bulb-apparatus used for the oxygen 
determinations, and thus the total loss of oxygen was estimated as well as the re- 
duced silver. The action proceeds more rapidly than in the experiments with the 
chloride and oxide, so as to render it probable that a more accurate result might in 
this manner be obtained with the carbonate than with those substances. In the first 
experiment the total loss was 12T9 per cent.; in the second, 11’91 per cent. The 
sum of the oxygen in the peroxide and that due to the silver reduced, as given by the 
determinations, is in the first experiment 1T84 per cent.; in the second, 12T6 per 
cent. ; which so agree with the other numbers as to show that no oxygen is retained 
by the substances. 
On turning to those experiments with the chloride of silver at 100° C. and at the 
lower temperature, with which these experiments are comparable (Tables I. and II.), 
it will be seen that the reduction is nearly the same with the two substances. 
With sulphate of silver the result was very different. The two following experi- 
ments were made with pure crystallized sulphate of silver and the peroxide Q, at 
100° C. In the first experiment one equivalent, in the second two equivalents of the 
sulphate were taken. 
Table XII. — A. 
Peroxide of 
barium (J. 
Sulphate of silver. 
Chloride of 
silver found. 
Equivalent of 
oxygen. 
1. 
2‘969 grms. 
5-449 grms. 
0-118 grm. 
0-00657 grm. 
2. 
3-005 
10-805 
0-542 
0-03021 
Table XII. — B. 
Oxygen in the 
Oxygen of the sul- 
peroxide of 
phate of silver 
Ratio, a : i/-. 
Calculated ratio. 
barium Q = a. 
reduced = ■v/'. 
1. 
8-58 
0-221 
40 : 1 
0-21 
2. 
1-00 
9:1 
0-95 
Table XII.- 
-c. 
Oxygen in the 
Oxygen of the sul- 
peroxide of 
phate of silver 
Ratio, a : ■>/'. 
Calculated ratio. 
barium Q=a. 
reduced = 
1. 
100 
2-57 
40 : 1 
2-5 
2. 
11-66 
9:1 
11-1 
The amount of reduction is here so small that the action of the sulphate of silver 
is very nearly the same as the so-called contact action of platinum. I have already 
pointed out that the action of very small quantities of the chloride and of the oxide 
of silver is also of the same nature. In the case of these different chemical sub- 
stances, therefore, it approaches the same limit, although according to a different law. 
