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Improving the magnetic properties of gamma-iron (III) oxide

  • US 4,212,903 A
  • Filed: 02/22/1977
  • Issued: 07/15/1980
  • Est. Priority Date: 11/09/1972
  • Status: Expired due to Term
First Claim
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1. A process for improving the magnetic properties of gamma-iron(III) oxide pigments which comprises:

  • applying to said gamma-iron(III) oxide pigments a basic compound selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides to provide a pigment crystal surface having a pH above 8, which basic compounds can be removed by elution of the said pigments after they have been heated at a temperature of from 400°

    to 700°

    C., andheating said pigments at a temperature of from 400°

    to 700°

    C., said surface crystal pH remaining above 8 throughout said heating step, whereby the magnetic properties of said pigments are improved.

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