Magnesium ferrite, Mg(FeO₂)₂

Magnesium ferrite, Mg(FeO₂)₂, occurs in nature as magnesio-ferrite and crystallises in the cubic system. It may be prepared in crystalline form by heating ferruginous magnesia to redness in a current of air and hydrogen chloride. It also results when sodium or potassium hydroxide is added to a solution of magnesium sulphate and ferric chloride, and the precipitate ignited. It is then obtained as a brown magnetic powder.