The Standard Free Energy of Formation of UI[sub 3] from EMF Measurements on a Solid Electrolyte Galvanic Cell

The first known experimental measurements of the Δ F ° f of UI 3 are described. The emf of the solid electrolyte galvanic cell, Pt / U , UI 3 ( s ) / NaI ( s ) / Agl ( s ) / Ag ( s ) / Pt , was measured over the temperature range of 220°–370°C. The Δ F values of the cell reaction U ( s ) + 3 AgI ( s ) ⇄ UI 3 ( s ) + 3 Ag ( s ) , derived from the emf data from six cells, were combined with the AF°f values of AgI to obtain the Δ F ° f of UI 3 . This resulted in a value of − 98.8 ± 0.4 kcal/mole at 370°C, which was 6.7 kcal/mole more positive than previously published estimated values.