1908-9.] Electromotive Force of Iodine Concentration Cells. 309 
solution was allowed to settle in the thermostat for some hours, a little 
quickly withdrawn in a graduated pipette through a plug of glass-wool, 
introduced into a flask containing some potassium iodide solution and 
titrated. The bottle was then closed, rotated for several more days, and a 
fresh sample removed and titrated. The second titration was found to 
agree very closely with the first, as the following figures show : — 
Table II.- — Iodine Saturations. 
No. of KI 
Molecules. 
No. of Iodine Molecules. 
•025 
•05 
T15 
•Q95 + -00134 > f n t er pMated nom Noyes s 
•0575 + -00134 ) results - 
1st Determination. 
2 nd Determination. 
Mean. 
•344 
T89 
T90 
T895 
•5 
•295 
•297 
•296 
•7 
•440 
•442 
•441 
•85 
•579 
•578 
•5785 
1-0 
•712 
•711 
•7115 
These values will be found to be a little higher than those obtained by 
Bruner,* but they have been taken as correct for the purposes of this paper. 
From these values, less the solubility of iodine in water, we obtain the total 
number of molecules of iodine in combination with the potassium iodide. 
The following table embodies the results obtained. Column I. gives the 
total number of potassium iodide molecules present ; column II., the total 
amount of uncombined KI as calculated from the E.M.F. ; column III., the 
total amount of combined iodine as obtained from the titration ; and column 
IV., the sum of the values in columns II. and III. 
Table III. 
I. 
No. of KI 
Molecules. 
11. 
Total 
Free KI. 
III. 
Total Com- 
bined Iodine. 
IV. 
Sum of 
1 1. + III. 
•025 
•0127 
0125 
•0252 
•05 
•025 
•025 
•05 
•115 
•056 
•0575 
•1135 
•344 
T57 
T89 
•346 
•5 
•22 
•295 
•515 
•7 
•273 
•440 
•713 
•85 
•307 
•578 
•885 
1-0 
■317 
•711 
1-028 
* Zeits. Phys. Chem. xxvi. 150. 
