Journal of the Mining Institute of Japan

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Dissolution phenomena of zinc ferrite in dilute sulphuric acids of different strength were studied by means of an agitating device which enables leaching to proceed at any desired. temperature and quantitative relations between temperature, acidity and extraction were determined. Tendencies were found to be quite similar with either the dead roasted marmatite or the pure ZnO-Fe₂O₃mixtures heated at 900°C. Velocity of dissolution is affected more strikingly by increase in temperature than by that in acidity. For example, at 80° as weak as 1% H₂SO₄which is almost inactive upon ferrite at 25° can extract more than. 40% of the zinc content in 6 hours, at 25° even 30 acid extracts less than 20% Roughly speaking, between 20° and 80°, every rise in temperature of 20 degrees makes an hour's leach a tain the same results as 6 hours' leach at the lower temperature.
It was confirmed by the experiment that in order to decompose greater parts of the ferrite in a reasonable time, leaching temperature should be above 60°, 30% H₂SO₄extracts but 77% of zinc from ferrite in an hour, while 96% are extracted by 18% acid at 80°.
The iron oxide which forms the zinc ferrite are attacked next to. the combined zinc oxide, while the surplus iron oxide existing in a free state is more refractory and for the most part remains undissolved.

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