| 摘要 |
<p>Mixtures of at least two of iron, nickel and cobalt oxalates are prepared by adding oxalic acid or an organic ester of oxalic acid, e.g. dimethyl oxalate to a mixture of the metal salts in the presence of ultrasonic vibrations. The vibrations have preferably a frequency of 10,000 to 90,000 cycles per second and the preferred mixture has from 30 to 50 mole per cent of cobalt, 40 to 70 mole per cent of iron and if nickel is used it may be between 2 to 20 mole per cent of the total. The precipitate after heating and drying may be heated in an inert gas or reducing atmosphere, e.g. hydrogen and may then be coated on a polymeric tape suitable for magnetic recording. Specification 1,007,901 is referred to.</p> |
