Process for obtaining hyperfine magnetite powder

摘要

A process is disclosed for producing magnetite having an equiaxial morphology in the state of a hyperfine powder, starting from a solution of a bivalent iron solution, characterized in that:P PA. AN AQUEOUS SUSPENSION OF Fe(OH).sub.2 is prepared by reacting an aqueous solution of a ferrous salt with alkali;PPB. SAID AQUEOUS SUSPENSION OF Fe(OH).sub.2 is fed into an autoclave into which is also introduced a quantity of air corresponding to 4-15 normal liters per 100 g of bivalent Fe; andPPC. THE AUTOCLAVE IS THEN BROUGHT TO A TEMPERATURE BETWEEN 150° AND 200° C and maintained at this temperature until the inside pressure has stabilized itself at a constant level, thereby bringing about the formation of the desired magnetite which, once discharged from the autoclave, is washed and dried. The aqueous suspension of Fe(OH).sub.2 subjected to thermal decomposition in the autoclave may have present therein Cu.sup.+.sup.+ion, in a quantity between 0.3 and 1.4% by weight of the bivalent Fe. When Cu.sup.+. sup.+ is present in the aqueous suspension of Fe(OH).sub.2 which is subjected to the thermal decomposition, it is also desirable to have dissolved therein Na.sub.2 S in such a quantity as to provide from 20 to 60 mg of S per 100 g of bivalent Fe.