| 摘要 |
PROBLEM TO BE SOLVED: To provide a stable coloring agent which is composed of a powder being excellent in heat resistance, having a little particle size and providing a stable black color, and can be suitably used as a black pigment for cosmetics or coating materials and as a magnetic powder for a toner in electrophotography. SOLUTION: The stable coloring agent comprises the reductant of at least one powder selected from iron oxide and ferrite. Preferably, the stable coloring agent has a black chromaticity (L) of 16 or less as measured by a colorimeter and a deterioration degree of 2% or less; and is produced by treating to reduce at least one raw material selected from iron oxide and ferrite under a reductive atmosphere and then triturating mechanically until the product has an average particle size of 0.7μm or less and a nitrogen absorption specific surface area (BET) of 6 m<2> /g or more.
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