Studies on the Solution of Cadmium in Molten Cadmium Chloride. II. Effects of Added Chlorides on the Solubility of Cadmium in Molten Chloride

Abstract

In order to study the effects of added chlorides on the solubility of cadmium metal in the molten cadmium chloride, its solubility in CdC1 2-KCl-AICl 3 mixtures was determined by measuring the EMF of C / Cd, CdC1 2-KCI-AlC1/ / CdC1 2-KCI-AlC13, Cd(sat.) / C cells. For the Cd-CdC1 2 s ystem, solubility limits were determined as 0.156 (molar fraction) at 600°C and 0.189 at 7 40°<:;:. It was found that these values increased with the addition of A1Cl 3-rich chloride mixtures, but decreased with the addition of KCl-rich mixtures. Assuming that Cd dissolves into molten CdC1 2 as Cd 2 2+ up to the solubility limit, these effects may be interpreted as an acid-base reaction between the added chloride and Cd 2 Cl 2 in CdC1 2 • A basic chloride such as KC 1 which acts as a Cl-donor stabilizes Cd 2 + ions, and an acidic chloride such as AlC1 3 (Cl-acceptor) decreases the stability of Cd 2+ ions. Based on results in which the contribution of the dilution effect of added salts was eliminated, an ~cidity scale that could quantitatively represent the stren. gth of acidity of chlorides was introduced.

Oxygen Electrode Reaction in a LiCl–KCl Eutectic Melt

“…Here the value at 723 K is 2.463 Ϯ 0.001 V vs Li + /Li. This result indicates that the previous study by Kanzaki and Takahashi,11 in which the standard electrode potential was determined by the measurement of emf using a platinum electrode, was more precise than the determination from the solubility of refractory metal oxides in the melt reported by Masuko et al 7 although the influence of a mixed potential was not completely avoided on a platinum electrode as described in the Introduction. It is also suggested that our previous study, estimated from the Li 2 O solubility, 12 is almost precise.…”

“…It affects the passivation phenomena on the surface of the produced metals 5 and plays an important role in acid-base reactions. 6,7 To understand the chemical and electrochemical behaviors of oxide ion in molten chlorides, it is necessary to determine the thermodynamic quantities of oxide ion such as chemical potentials in molten chlorides.…”

“…Consequently, it was suggested that the oxygen electrode reaction was influenced by the presence of the peroxide ion, O 2 2− , or the superoxide ion, O 2 − . The standard formal potential of O 2 /O 2− was investigated in a LiCl-KCl eutectic melt at 723 K. The value calculated from the solubility of refractory metal oxides by Masuko et al was 2.97 V ͑vs Li + /Li͒, 7 while that estimated from the electromotive force ͑emf͒ by Kanzaki and Takahashi using a platinum electrode as an anode was 2.453 V ͑vs Li + /Li͒. 11 We have also recently estimated it to be 2.472 Ϯ 0.001 V ͑vs Li + /Li͒ from the solubility of Li 2 O determined for a LiCl-KCl eutectic melt.…”