Preparation of acicular .alpha.-Fe.sub.2 O.sub.3
AssigneeBASF SE
InventorsVolker Arndt, Helmut Auweter, Rainer Feser, Ekkehard Schwab
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Abstract
Finely divided acicular and pore-free .alpha.-Fe.sub.2 O.sub.3 is prepared from an iron(III) salt in the presence of one or more organic substances which form complexes with iron(III) ions, in alkaline supension at from 80.degree. to 250.degree. C., and is used for the preparation of magnetic materials suitable for magnetic recording media.
Claims4
In an improved process for the preparation of finely divided, dendrite-free and pore-free tin-containing .alpha.-Fe.sub.2 O.sub.3 by precipitating iron(III) hydroxide from an aqueous solution of iron(III) salt in the presence of tin ions at a pH of from 6.0 to 8.0 by adding an alkali metal hydroxide to an aqueous iron(III) salt solution containing from 10.sup.-3 to 4.times.10.sup.-2 mole of tin salt per mole of iron(III) salt at a temperature of from 30.degree. to 70.degree. C. and heating the aqueous suspension of iron(III) hydroxide at a temperature of from 80.degree. to 250.degree. C. at a pH of from 8.5 to 12.0 after the addition of at least one compound capable of forming complexes with iron(III) ions, the improvement which comprises:
- heating the precipitated iron(III) hydroxide in the form of the resulting unfiltered aqueous suspension containing less than 0.6 mole of iron(III) hydroxide per liter.
Dependencies are inferred from the claim text.