Journal of the Mining Institute of Japan

The object of this paper is to give the results of research into the resistance caused by standing tubs in mine airway. The model airway and tubs were to a scale of 1/10th fullsize. The test velocities were 1-2m/sec and a test length 8m was chosen and the pressuredrop was measured at stations up-stream and down-stream of test length. Gettingen type Pitot tubes with two Askania rvIinimeters were used for the prssure and velocity measurements.

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The formation of the slime in the iron electrolytic refining bath is mainly caused by the oxidation of iron ion. So, the principal components of slime are iron hydrous oxides. The mechanism of oxidation was examined and electrolytic experiments were carried out. Then, the composition and structure of the slime were discussed on the basis of the chemical analyses, the measurements by thermo-balance and the physicochemical tests. The main results obtained are as follows:
1) Ferrous ion in sulfate bath is precipitated as hydroxides of iron by hydrolysis, but its amount is small.
2) Anodic formation of Fe (OH) ₂ is due to the high potential of anode caused by high current density, or some metalographic structures, especially in the case when the anode shows high dissolution overvoltage or anodic passivity.
3) Fe (OH) ₃ is precipitated around the cathode as the result of srecondery reaction cauted by the liberation of hydration watere molecule of discharging iron ion which is believed to be aqeous complexion. The amount of this is not small.
4) The precipitates of Fe (OH) ₂ and Fe (OH) ₃ contain a large amount of water, and are cosedimentated with salts in the bath.
5) Therefore, the slime is voluminous and difficult to be filtered, but it may be separated by the sedimentation method. This method is covenient to apply for the separation of the slime in the ferrous sulfate-ammonium chloride bath.

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