Jens H. Von Barner

Electrochemical Investigation on the Redox Chemistry of Niobium in LiCl ‐ KCl ‐ KF ‐ Na2 O Melts

The system LiCl-KCl-KF-1 mole percent K 2 NbF 7 (molar ration F/Nb = 8) has been investigated in the temperature range 370 to 725°C by cyclic and square wave voltammetry. In the temperature range from 370 to 520°C Nb(V) was reduced to Nb(III) in two reversible steps: Nb(V) → Nb(IV) → Nb(III). At these temperatures subvalent halides of niobium were formed at more negative potentials. At temperatures above 660°C metallic niobium was formed during reduction. When oxide (molar ratio O 2 /Nb = 1.1) was introduced in the melt at 725°C only minor changes were observed in the voltammograms. It is suggested that oxide addition mainly leads to precipitation of oxide containing compounds.

Potentiometric and Raman spectroscopic study of the complex formation of Mg(II) in KClAlCl3 melts

Abstract Potentiometric measurements with chlorine-chloride concentration cells and Raman spectra of dilute solutions of Mg(II) in basic KClAlCl3 melts give evidence for the complex equilibrium MgCl42− ⇌ MgCl3−+Cl− with a pK value at (based on molar concentrations) between 1.94 and 2.43, 350°C. In an acid melt (pCl− = 5.98) the Mg2+ ion is shown to exist.