Patent · US Expired

Manufacture of gamma-iron(III) oxide

US4061725A · kind A · utility

7Cited by

3References

7Claims

0Family size

Assignee

BASF SE

Inventors

Manfred Ohlinger · Bischofswerda, DE
Eduard Schoenafinger
Walter Schneider · Thalwil, CH
Heinz Stritzinger · Ludwigshafen, DE
Guenter Vaeth · Schifferstadt, DE

Key dates

Filing date	Oct 15, 1976
Grant date	Dec 6, 1977
Priority date	—
Expiry date	Oct 15, 1996

Classification

Technology area (CPC C)Chemistry; Metallurgy
CPC primaryC01P2006/11
WIPO fieldAudio-visual technology
WIPO sectorElectrical engineering

Abstract

Acicular gamma-iron(III) oxide is manufactured by reacting an iron(II) salt solution with an aqueous solution of an alkali metal hydroxide and oxidizing the resulting suspension of iron(II) hydroxide in three stages. In a first stage, at most from 0.1 to 4% by weight of the amount of iron(II) hydroxide originally present is oxidized in the course of from 0.1 to 4 hours, in a second stage from 10 to 25% by weight of the said original amount are oxidized in the course of from 1.5 to 6 hours and in a third stage the remaining amount is oxidized. After the oxidation, the goethite formed is reduced to magnetite and the latter is then oxidized to acicular gamma-iron(III) oxide.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.