Thermodynamic Study of Oxygen in Liquid Elements of Group Ib to VIb

Abstract

The activity coefficient of oxygen in liquid cadmium at 773 K was measured by the electrochemical technique employing a solid electrolyte. Two empirical correlations of the thermodynamic values for oxygen dissolution between the elements of group Ib to VIb have been established in this paper on the basis of the data previously obtained by a modified coulometric titration method. By combining the measured value at 773 K with one of the correlations, the standard Gibbs energy of solution of oxygen in liquid cadmium for 1/2 O₂ (101325 Pa)→O (1 mol%) has been determined as a function of temperature as follows:
ΔG°(in Cd)⁄J·mol⁻¹=−142540+9.4(T⁄K).
The standard Gibbs energy of formation of CdO in the range of 742 to 831 K was experimentally determined using a similar electrochemical cell. The result is
ΔG°(CdO)⁄J·mol⁻¹=−261510+106.9(T⁄K).
The saturation solubility of oxygen in liquid cadmium calculated from the combination of these two results is
C_s(in Cd)⁄mol%=exp{11.73−14309⁄(T⁄K)}.
Based on the foregoing two correlations, the standard Gibbs energies of solution of oxygen in liquid zinc, aluminium, silicon, arsenic and selenium have been evaluated as follows:
ΔG°(in Zn)⁄J·mol⁻¹=−213400+19(T⁄K),
ΔG°(in Al)⁄J·mol⁻¹=−364800+41(T⁄K),
ΔG°(in Si)⁄J·mol⁻¹=−290700+37(T⁄K),
ΔG°(in As)⁄J·mol⁻¹=−119600+16(T⁄K),
ΔG°(in Se)⁄J·mol⁻¹=−43800+37(T⁄K).