Process for preparing acicular iron oxide particles

This disclosure relates to a process for preparing acicular magnetic iron oxide particles by (a) adding an aqueous solution of a ferrous salt to an aqueous solution of a stoichiometric excess of alkaline hydroxide while substantially avoiding local excesses of the ferrous salt, to form an aqueous dispersion of ferrous hydroxide particles, (b) oxidizing these particles to form non-magnetic alpha ferric oxide hydrate particles, and (c) converting the non-magnetic particles to magnetic iron oxide particles by dehydration and reduction or dehydration, reduction and oxidation. The ferrous salt solution is subjected to reducing conditions prior to and/or during the addition to the alkaline hydroxide solution to reduce contaminating ferric ions that are normally present to ferrous ions.