In the previous report, two main processes relating to the direct reduction of aluminum were described in detail, namely the one is the carbothermic production of crude aluminum alloys and the other is the decomposition method using carbide, nitride, etc., and especially we discussed on the former process.
In this report, the experimental results of equilibrium, Kinetics and refining of the subchloride process are described. Furthermore, various other industrial examination for the refining of aluminum from crude alloys are also discussed on the basis of published papers and patents.

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In order to develop an efficient rock excavation method for hard or super-hard rock formations, a method using the mechanical rock-cutting device combined with thermal action by flame has been experimentally studied.
In this paper, the results obtained in the experiments are presented and discussed. Then, a new idea for the evaluation of the efficiency in the mechanical rock-cuttings in which the thermal action by flame is used at the same time has been proposed.

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The effects of flow of methane-air gas on its explosion were investigated by using steel pipes of 102-385 mm diameters and 10-30m lengths. The results obtained are as follows.
The flow of methane-air gas has an effect on flame speed in case of the closed end ignition (the other end is open): the flame speed increases with the increase of flow speed in the range of 0-0.7m/s and takes nearly constant, maximum speed in the range of over than 0.7m/s, which is about twice than flame speed in the case of explosion of stationary methane-air gas. It may be said turbulent explosion takes place in pipe explosion as well as turbulent combustion in chamber combustion.

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In a previous paper dealing with the removal of Cd²⁺ ions with xanthate, it was shown that xanthate was excellent as a selective precipitant and that Cd²⁺ ions could be removed selectively from mine water containing appreciable amount of Fe²⁺ and Zn²⁺ ions. It is the purpose of this paper to report some results on the removal of Cu²⁺ ions by use of xanthate.
The residual concentration of Cu²⁺ ions can be reduced to the water quality criterion by use of suitable amount of methyl xanthate. The use of excess amount of methyl xanthate, however tends to decrease the removal per cent of Cu²⁺ ions. Analysis of Cu²⁺ ions in the filtrates of residual solution of flotation indicates that the decrease in the removal per cent of Cu²⁺ ions is ascribed to the suspended fine particles of Cu-xanthate precipitates. The dispersion of fine particles of Cu-xanthate becomes appreciable when the peripheral speed of the impeller of flotator was small. The effect of aeration by which Cu-xanthate particles are flocculated may be interpreted in terms of “pseudo-flocculation”, i. e. the flocculation of particles through air bubbles.
The influence of coexisting ions such as Fe²⁺ and Zn²⁺ ions on the removal of Cu²⁺ ions with methyl xanthate is smaller than that on the removal of Cd²⁺ ions with iso-butyl xanthate.
There are many cases where mine water contains both Cu²⁺ and Cd²⁺ ions. Accordingly, in the case of removal of Cd²⁺ ions from mine water by use of higher xanthates, an amount of higher xanthates that are expensive is consumed by coexisting Cu²⁺ ions. In order to reduce the amount of expensive higher xanthate, it is recommended that Cu²⁺ ions are removed by methyl xanthate prior to the removal of Cd²⁺ ions with higher xanthate.
In the system containing both Cu²⁺ and Zn²⁺ ions, Cd²⁺ ions are coprecipitated with Cu-methyl xanthate. The dosage of methyl xanthate which is used to remove Cu²⁺ ions should be minimized in order to avoid the coprecipitation of Cd²⁺ ions. Thus, after removing Cu²⁺ ions by methyl xanthate 1.25 equivalent to Cu²⁺ ions (in the case where initial concentration of Cu²⁺ ions is 10mg/l) or 1.5 equivalent to Cu²⁺ ions (in the case where initial concentration of Cu²⁺ ions is 3mg/l), Cd²⁺ ions, the initial concentration of which is 1mg/l, can be reduced to the water quality criterion by the addition of iso-butyl xanthate 2.5-3.0 equivalent to Cd²⁺ ions.

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The removal of Hg²⁺ has been studied by the flotation technique.
Ethyl xanthate and ethyl aerofloat were used as collectors forming insoluble and hydrophobic Hg²⁺ salts.
The solutions containing 1.0 or 10.0ppm of Hg²⁺ were treated with collectors by a Denver Sub A type. flotator, then the residual solutions were analysed spectrophotometricaly by the dithizon method.
By the flotation technique, it was found that residual Hg²⁺ concentration was reduced to 0.06ppm while by the filtration technique it was below 0.02ppm.
The effect of coexistence of metal ions such as Fe²⁺, Cu²⁺, Zn²⁺ and Cd²⁺ on the removal of Hg²⁺ was also examined and the removal of Hg²⁺ was found to be prevented to a certain extent by these metal ions. However lower xanthate and aerofloat were found to be suitable for the removal of Hg²⁺ from the waste water containing these other metal ions.

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Some experiments were carried out to examine some behavior of thiourea in electrolytic refining of copper.
Thiourea is stable in pure water but becomes unstable when cupric ions exist and temperature rises. The presence of metallic copper in electrolyte makes thiourea stable.
The amount of thiourea diminishes during electrolysis, and the rate of diminition is proportional to the amount of electric charge flowed.
When the electrolysis is carried out immediately after adding thiourea to the electrolyte, sulfur from thiourea is easily included in electrodeposited copper and the quantity of the included sulfer is proportional to the amount of initially added thiourea. On the other hand, if the electrolysis is started after keeping the electrolyte containing thiourea at 60°C for about 90 hours and making almost all thiourea decompose, very small amount of sulfur is included in the copper, and the property of thiourea to make cathode surfaces smooth is still effective.

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The present investigation was undertaken to determine continuously the oxygen concentration in molten copper using solid electrolyte cell technique.
The oxygen concentration ranges investigated were 40-2000ppm.
The cells used were as follows;
P_t, Air/Z_r0₂ (+CaO)/O (in liq. Cu), Mo
P_t, Ni, NiO /Z_r0₂ (+CaO) CO (in liq. Cu), Mo.
From these experimental results it was found that the oxygen concentrations estimated by e. m. f. values were good agreement with those chemically determined ones.
Furthermore, the durability of calcia stabilized zirconia solid electrolyte was also investigated.

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