Molten potassium thiocyanate: reactions with compounds of chromium

Abstract

The solubility, spectra, and reactivity of potassium chromate, dichromate, and trichromate, chromium(VI) oxide, chromium(III) chloride, potassium hexathiocyanato-chromate(III), and chromium(II) chloride in fused potassium thiocyanate at 200° were studied. The chromium(IV) compounds were all reduced to chromium(III) species, initially in most cases to a soluble green form which was then precipitated as chromium(III) oxide. The oxide reacted further with the melt eventually giving black chromium(III) sulphide. Anionic products found in the melts after reaction included sulphide, sulphate, thiosulphate, cyanate, cyanide, nitrate, and oxide. The influence of added anions (potassium cyanate and cyanide, sodium monoxide and sulphide, etc.) on the absorption spectra and speed of precipitation were investigated and correlated in terms of the co-ordination of the chromium ions.