236 JONES AND SCHUMB. 



0.05 N and 0.02 N potassium iodide, saturated with iodine, was 

 measured against the decinormal calomel electrode at 25° and 0° with 

 the following results (uncorrected for liquid junctions): 



25° 0° 



■ Pt,l2sat., 0.1NKI,0.1NKCl,Hg2Cl2,Hg; E = -0.2804V. -0.2753v. 



Pt, I2 sat., 0.05 NKI, 0.1 NKCl.HgoCla.Hg; E = -0.2976 -0.2909 



Pt, I2 sat., 0.02 N KI, 0.1 N KCl, Hg2Cl2, Hg; E = -0.3200 -0.3114 



From these results the normal potential of the iodine electrode is 

 computed to be: 



25° 0° 



Pt, 1 molal I2, 1. N I- 1.0 N KCl, HgzCU, Hg; E = -0.3406 v. -0.3399 v. 



6. From the foregoing results the following results are computed 

 for the reaction: Tl (solid) + I/2 L (solid) = Til (solid): 



25° 0° 



Free Energy of Formation (A) 125 . 79 kj. 125 . 48 kj. 



Heat of Formation (U) 122 . 11 kj. 



This investigation has been aided bj^ a grant from the Cyrus M. 

 Warren Fund of the American Academy of Arts and Sciences, for 

 which we wish to express our appreciation. 



H-^RVARD University, 

 Cambridge, Mass. 



