Nadelförmige Hämatitteilchen und magnetischer Aufzeichnungsträger

摘要

Acicular hematite particles having an average major axis diameter of from 0.004 to 0.295 mu m, a geometrical standard deviation of the minor axis diameter of not more than 1.35 and a pH of not less than 8, which particles contain not more than 300 ppm of soluble sodium salt, calculated as Na and not more than 150 ppm of soluble sulfate, calculated as SO4.