Thermodynamics of the cadmium-amalgam electrode in aqueous medium

Abstract

From e.m.f. measurements of the cell: Pt| Cd x Hg 1−x| CdCl 2,aq , m = 0.1 mol kg −|AgCl|Ag|Pt over the temperature range from 288.15 to 308.15 K, the standard potential of the cadmium-amalgam electrode has been determined, which can be reproduced by the equation: E° Cd + Hg V = −0.3736907 − 2.099557 × 10 −5( T K ) 2 . The parallel values of the standard potential of the cadmium electrode have also been recalculated from data in the literature and have been found to be representable by E° Cd V = −0.1991361 − 1.29106× −3( T K )+2.099557×10 −6( T K ) 2 . From E Cd + Hg o and E Cd o have been determined the standard thermodynamic functions at 298.15 K for the cadmium amalgamation reaction and for the species: cadmium amalgam, CdCl 2(aq) and Cd 2+(aq). Dilute cadmium amalgams behave as regular solutions as substantiated by the linear relation between the logarithm of the rational activity coefficient of cadmium in amalgam and the corresponding mole fraction: log 10 ƒ Cd = Qx , where in turn the parameter Q is a linear function of temperature: Q = 0.039362+8.3999×10 −4( T K ) .