IOWA ACADEMY OF SCIENCES. 
185 
be determined, then dropping to the final temperature and 
running for at least one hour. This was done to insure 
saturation. Five hours agitation was found to be sufficient 
time. At the end of this period the precipitates were 
allowed to settle, a portion of the clear liquid pipetted off 
and weighed, the Ag precipitated by ammonium sulphide, 
filtered off, washed, dissolved in hot HN0 3 , precipitated as 
AgCl with HC1, collected in a Gooch crucible, washed, dried 
and weighed, the Agl in solution being calculated from the 
Ag found. The number of c.c. of the thiosulphate solution 
used was found from the weights by deducting weight of 
Agl and dividing by sp. gr. of this solution. In the later 
experiments the Ag was determined in the HN0 3 solution 
by means of Volhard’s method. 
The agitator used was similar to that used by Richards 
and Faber based upon the Noyes’ Apparatus, consisting of 
a wooden roller rotating in a large bath regulated by an 
Ostwald thermostat. The rubber stoppered tubes were 
strapped to the roller by means of rubber bands, the roller 
being driven by a small hot air engine. 
The solubility of the silver iodide is shown by the follow- 
ing tabular statement, N and N/2 solutions being used. 
Temp. 
Time of 
Agitation. 
Na 2 S 2 0 3 5H 2 0 to 
100 c.c. sol. 
Agl dissolved to 
100 c.c. sol. 
Ratio Agl in mol's 
to 1 mol. 
Na 2 S 2 0 3 5H 2 0 . 
20° 
7 hours 
24.83 
© 
.9613 
. 040945 
25 
8 hours 
24.83 
1.0380 
.044211 
35° 
8 hours 
24.83 
1.1870 
.050558 
50° • 
6 hours 
24.83 
1.4115 
.060129 
20° 
6 hours 
12.415 
.4173 
.035549 
25° 
6 hours 
12.415 
.4564 
.038865 
35° 
7 hours 
12.415 
.5277 
.044953 
From the accompanying diagram the effect of tempera- 
ture upon solubility is clearly seen, the amount of Agl dis- 
solved increasing quite rapidly with the increase of tem- 
perature, and the solubility curve being practically a 
straight line. After standing some time the Agl in the 
tubes begins to blacken, probably caused by a slight decom- 
