312 
j * 1 **&&■*»* 
iodine in normal KI at one electrode (the value of k being for this solution 
*001365), and the series of strengths of iodine given in Jakowkin s table at 
the other electrode, up to and including *508 of iodine. These values were 
measured at 20*4° C., but have been corrected for 25° C. and included in 
Table IV. Additional measurements have also been made for stronger solu- 
tions up to and including the saturation-point. These E.M.F.’s are also given 
in Table IV., as well as the correction for contact E.M.F. as determined for 
certain of the solutions. Graph 3 shows the E.M.F.’s plotted against the 
7 
* 
- 6 
E 
o 
c 
C '5 
V) 
_a> 
3 
O 
- 4 . 
o 
2 
a) 
c 
-a '3 
o 
o 
t. _ 
a) '2 
-O 
E 
3 
z 
1 
Volts -001 002 -003 004 005 006 007 008 
10 normal Ammonium Nitrate corrections for Iodine in normal KI 
Graph 4. 
iodine concentrations. Graph 4 shows the corrections plotted against the 
iodine concentrations. 
These results can also be used to calculate the number of iodine ions in 
the strong solutions. For, in the dilute solution of iodine we can calculate 
the amount of free iodine present from the value given by Jakowkin for K 
for this solution, namely *001365, and we can without serious error assume 
the number of iodide ions present to be given by the ionisation ratio for 
normal KI. On the other hand, the amount of free iodine at the strong 
iodine electrode can be calculated by using the value of k as determined 
by Jakowkin for that particular strength of solution. 
It is true that Jakowkin has not determined the value of k for strength 
Proceedings of the Royal Society of Edinburgh. [Sess. 
