IOWA ACADEMY OF SCIENCES. 
180 
than will combine with the iodine, and which probably, 
then, exists as Ag 2 0. 
The starting of this reaction requires an excess of AgI0 3 
and seems to be due to the formation of Ag 2 S setting free 
acid. It might be accounted for by the occurrence of such 
a reaction as the following: 2AgI0 3 + Na 2 S 2 0 3 + H 2 0 = 
Ag 2 S + 2HI0 3 + Na 2 SO 4 . When the thiosulphate is in 
excess no reaction takes place, but on the addition of the 
slightest amount of free acid the reaction begins. 
It is practically impossible to obtain even a close ap- 
proximation of the solubility of silver bromate in thiosul- 
phate because of the fact that the substances begin to react 
within ten minutes after they are put together, hence 
saturation could not be obtained. In a trial at this 100 c.c. 
N/10 thiosulphate solution disol ved 1.835g. AgBr0 3 . 
For studying this reaction the AgBr0 3 and the Na 2 S 2 0 3 
were put together molecule for molecule and after thorough 
shaking for several hours were allowed to stand for a week. 
Qualitative tests show that the solution contained no 
thiosulphate, no silver, a little bromic acid, sulphuric acid 
either free or as sulphate, and hydrobromic acid; the 
residue contains silver bromide, free sulphur, but no silver 
sulphide. 
On analysis the following results were obtained, using 
the same methods as in the iodate reaction: 
Weight of AgBr0 3 taken 6491g. 
N/10 thiosulphate taken 27. 52c. c. 
Filtrate was made to 150 c.c. and 40 c.c. taken for each 
determination. 
Weight BaS0 4 .3I62g. Total S as sulphate 16283g 
Weight of free S in residue 0130g 
Total sulphur found 17583g 
Total sulphur in Na 2 S 2 0 3 used 17610g 
Dried residue was treated with hot HN0 3 washed, dried 
and weighed as AgBr. 
Weight of AgBr .3883g., weight Ag found 22305g 
Weight Br found 16525g 
