Claims
- 1. Poreless, plate-shaped magnetite particles having an average particle diameter of 0.1 to 0.5 .mu.m, a plate ratio of 11:1 to 20:1 and a specific surface area of 2.0 to 30.0 m.sup.2 /g, which particles are discrete from each other.
- 2. Poreless, plate-shaped magnetite particles according to claim 1 obtained by:
- (a) reacting a ferrous salt solution containing 0.2 to 5.0 mol % of a ferric salt, calculated as Fe(III), based on Fe(II), and an aqueous alkali carbonate, the amount of which is controlled so that the equivalent ratio of the alkali carbonate to the Fe(II) and Fe(III) in said aqueous ferrous salt solution is not less than 1, and the following formula is satisfied: ##EQU6## the concentration of Fe(II) and Fe(III) in the suspension being less than 0.3 mol/l; and
- (b) oxidizing the thus-obtained FeCO.sub.3 -containing suspension by passing an oxygen-containing gas therethrough.
- 3. Poreless, plate-shaped magnetite particles according to claim 1 obtained by:
- (a) reacting a ferrous salt solution containing 0.2 to 5.0 mol % of a ferric salt, calculated as Fe(III), based on Fe(II), and an aqueous alkali carbonate, the amount of which is controlled so that the equivalent ratio of the alkali carbonate to the Fe(II) and Fe(III) in said aqueous ferrous salt solution is not less than 1, and the following formula is satisfied: ##EQU7## in which from 0.01 to 8.0 mol % of a water-soluble organic compound having a --COONa or --COOK group, based on said Fe(II) and said Fe(III), are added to said aqueous ferrous salt solution to produce a suspension containing FeCO.sub.3, said aqueous alkali carbonate solution and the suspension containing FeCO.sub.3 before oxidation and a concentration of Fe(II) and Fe(III) in the suspension being not less than 0.3 mol/l; and thereafter
- (b) oxidizing the thus-obtained FeCO.sub.3 -containing suspension by passing an oxygen-containing gas therethrough.
- 4. Poreless, plate-shaped magnetite particles having an average particle diameter of 0.1 to 0.5 .mu.m, a plate ratio of 21:1 to 50:1 and a specific surface area of 3.0 to 30.0 m.sup.2 /g, which particles are discrete from each other.
Priority Claims (1)
Number |
Date |
Country |
Kind |
1-140091 |
May 1989 |
JPX |
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Parent Case Info
This is a continuation of application Ser. No. 07/526,819, filed May 22, 1990, now abandoned.
US Referenced Citations (4)
Foreign Referenced Citations (1)
Number |
Date |
Country |
306224 |
Mar 1989 |
JPX |
Non-Patent Literature Citations (1)
Entry |
Patent Abstracts of Japan, vol. 13, No. 457 (C-644) (3805), Oct. 16, 1989 and JP-A-1 176 233 (Toda Kogyo). |
Continuations (1)
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Number |
Date |
Country |
Parent |
526819 |
May 1990 |
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