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IOWA ACADEMY OF SCIENCES. 
solution, no hydriodic acid was present, but a small quan- 
tity of iodic acid was found. A determination of the sul- 
phuric .acid in the solution and the amount of sulphur 
combined with the silver and in the free state accounted 
for all the S in the Na 2 So0 3 used, showing complete de- 
composition of the thiosulphate. In a similar experiment, 
in which the substances were allowed to stand for about a 
week, the residue contained no silver sulphide, showing 
that the formation of Ag 2 S is an intermediate reaction 
and that the reaction of the first experiment did not com- 
plete itself in the time allowed it. 
For the determination of the products of the reaction the 
following methods were pursued. The residue was filtered 
off, washed, and the filtrate and washings made up to 
100 c.c., portions of 20 c.c. being taken for analysis. The 
sulphates were precipitated by means of barium chloride 
and weighed as barium sulphate. To determine the iodic 
acid the solution was digested for several hours with 10 c.c. 
cone. HC1 and KI in a closed bottle, the free iodine being 
then titrated with N/10 thiosulphate and the iodine found 
as HI0 3 calculated. The residue was dried at 110°, the free 
sulphur extracted by repeated treatment with hot chloro- 
form, the chloroform evaporated and the sulphur weighed. 
The following results were obtained from the analysis of 
the completed reaction : 
Weight of AgI0 3 taken 4046g. 
c.c. N/10 thiosulphate 14.31=Na 2 S 2 0 3 5H 2 O. . .3553g. 
Weight of BaS0 4 .1124g. , total S as sulphate . . . .07718g. 
Free S in residue .0178g. 
Total sulphur found. 09498g. 
Sulphur in thiosulphate taken 09158g. 
Total iodine in HI0 3 in filtrate .... 03530g. 
Iodine as HI None. 
Total iodine in AgI0 3 used 1815g. 
Hence iodine in residue 1462g. 
The iodine in the residue is in combination with silver 
as Agl, excepting the possibility of a very small quantity 
of AgI0 3 undecomposed in the reaction. There being no 
Ag in the solution, there must be more Ag in the residue # 
