Preparation of “Mischmetall” by Thermal Reduction

Abstract

A method of preparation of “mischmetall” by thermal reduction of mixed fluorides of rare earth metals, using calcium as reducing agent, has been submitted to an experimental investigation. Raw materials were ores from the Belgian Congo from which, by using well‐known chemical methods, mixed oxides of rare earth were extracted.The preparation of the mixed fluorides was carried out in two steps. First, double fluorides of rare earth and ammonium were produced by reaction of the mixed oxides with ammonium bifluoride; then the double fluorides were decomposed by heating; ammonium fluoride being volatilized, the mixed fluorides can be easily recovered.The mixed fluorides were submitted to thermal reduction with calcium with addition of a small amount of iodine. The reaction is self‐supporting and small ingots of misch‐metall were obtained with a fairly good efficiency.