190 
IOWA ACADEMY OF SCIENCES. 
The A g found in the filtrate from the AgBr was precipi- 
tated as AgCl by HC1 and weighed in a Gooch crucible. 
Weight of AgCl .0976g., weight of Ag found ...... .07347g. 
Total silver found 29652g. 
Total silver in AgBr used 29700g. 
Weight of AgBr in 40 c.c. , original filtrate. 0280g. 
Weight of Br found as HBr 04468g. 
Weight of Br found as HBrO >3 .0091g. 
Weight of total bromine found 2I903g. 
Weight of bromine in AgBrOg taken 2200g. 
From the above analysis there seems to be silver in the 
residue which cannot be in combination with either Br or 
S, and hence probably exists as Ag 2 0, being undissolved by 
the very weak acid solution formed in the reaction. 
There seems to be in general a similarity between the 
reactions of AgIG s and AgBr0 3 with sodium thiosulphate 
solutions. In both reactions the Ag 2 $, which is at first 
formed, entirely disappears if the reaction be allowed to 
go to completion. The essential difference in the reac- 
tions seems to be the presence of HBr in the bromate 
reaction, while HI is absent from the iodate reaction, 
though a larger amount of HIO y is found in the latter 
than HBr0 3 in the former. 
Chemical Laboratory of Iowa College, Grinnell, Iowa. 
