Process for the preparation of a synthetic RHOMBOEEDRISCH magnetite, AND SYNTHETIC RHOMBOEEDRISCH magnetite, DAT according to this process can be prepared.

摘要

In a process for producing a synthetic rhombohedral magnetite comprising the steps of: A. Contacting ferrous chloride solution having an Fe++ concentration of from 0.87 to 3.0 moles per litre with at least a stoichiometric amount of carbonate ion; B. aerating the mixture at a temperature of from 70-90 DEG C so as to oxidize the iron to magnetite having a Fe++/total Fe++ and Fe+++ ratio of from 0.25-0.38; and C. recovering the magnetite so produced, the improvement which comprises providing the carbonate in the form of finely divided particles of an average size of less than 3.5 microns. The magnetite may be calcined at a temperature of from 650 DEG -925 DEG C. In the presence of oxygen to produce alpha ferric oxide. Also claimed is a synthetic rhombohedral magnetite having a BET surface area of greater than 13 m2/g and an average particle size of less than 0.08 microns as measures along the long axis.