The previous paper described the first experiment in laboratory on the underground gasification of coal by using only air. This paper describes the gasification of coal by using oxygen. The purpose of this experiment was to know the outline of gasification processes which took place by using oxygen. The author concludes as follows;
1. By using oxygen, the calorific value of gas is greater than that by using air only.
2. The gasified zone is also greater. In our experimental apparatus-the amount of oxygen is 3. 2l/min, length of borehole 30cm and diameter of this hole 1. 2mm-we could get the gas, of which calorific value is more than 1000 kcal/Nm³, during about 10 hours.
3. By using oxygen, we can get the desirable gas. But what amount of gas is much desirable in this case? What reduction process occurs in coal seam?
Can we get the reaction speed in gasification process of coal? Many experiments about these themes were carried out in our laboratory, and that will be described in next paper.

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A rotary bit penetrates into the rock along a helical path under the action of an axial thrust force and a rotary torque and the action of the cutting tip is one of planing. It seems reasonable to assume, therefore, that a study of the planing action of a tool on rock would reveal much information to rotary drilling or boring.
Then, we have studied on the following problems using a rock planing apparatus which is able to measure horizontal and vertical component of cutting resistance of rock: 1) effect of depth of cut, 2) effect of number of free surface, 3) effect of width of cutting tip, 4) effect of wear of cutting tip, etc.

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The object of this study is to discuss how the shear strength of rocks, which is necessary for analytical, studies of rock fadure in drilling, blasting and in strata control, should be measured.
It is considerecithat the methods for measuring the shear strength may be classified following two. Namely, (T) rhe shear strength (I) is measured by the nominal stress (P-A), where P is the shearing force and A is the areo of the shear plane, and (2) the shear strength (II) is measured by the calculation of the stresses actina or the plane of shear fracture.
In this study, a double shear test was carried out for (I), and the Mohr's construction method, in which the shear strength would be found from intersection o fτ-axis and Mohr's envelope, was carried out for (II). The Mohr'senvelope is represented by the par Gbolic curve in this tast. And this Mohr'senvelope is guessed to be useful for measuring the shear strength in rock strata.
The results are as follows; the shear strength (I) by double shear test is calculated larger than that (II) bv Mohr's envelope, because the normal stress acts on the shear plane in the former test.Also, in the double shear te: st under the tri-axial pressure, the regularity of the sheared surfaces increases as the confining pressure increcses.

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To consider the basic mechanisms of levitation in view of the flotation as a rate process, it is revealed that the significance of flotation, rate is not limited to the directly economical phases of flotation practice such as throughput, power consumption, etc., but the more essential feature of flotation rate is its character as a measure of floatability, which makes feasible the rational approach to the floatative separation process in practice.
The authors discussed the theoretical basis of the flotation rate function, as derived from the analytical consideration of the possible mechanisms of levitation. As a result, it was suggested that the 1st order rate equation could be the only resultant form that is theoretically plausible, and also that the deviation from the ideal equation (“anomaly”) may be caused by (1) any “unevenness” of the flotation characteristics of the mineral particles in question, due, e.g, to variation of floatability, size, etc., by (2) the “inter-dependence” of levitation of each particle in the system, and/or by (3) and the mutua I interferential effect amorg the flotation mechanisms presumed.
Some batch flotation tests were conducted on the quartz-amine system in order to investigate the flotation rate function in relation with the flotation variables such as activity of mineral particles, particle size, pulp density, aeration rate, and intensity of agitation. Anomaly was determined on the experimental graphs in so unessential a degree, within the range studied, that the approximate representation of the flotation rate function by the 1st order equation was accepted for a group of “similar” particles from a practical point of view. It was concluded from the experimental results that the anomaly was mostly attributed to the “unevenness”-distribution of flotation rate constant-of the mineral particles concerned.
The rate of flotation was proved to change with the flotation variables studied. Among others, the combined effect of change in activity of mineral particles and particle size on the flotation rate function will deserve further inquiry.

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It has been generally considered that major substances suspended in zinc electrolyte are lead compounds such as PbO₂, PbO, PbSO₄, Pb and manganese dioxide particles. The experiments, were -made on various properties of these particles in the solution, i. e., the variations of coagulation, electrophoresis, settling rate of suspension, pH value etc. From theabove experiments, it was considered that lead peroxide particles, which aremost harmful in zinc deposit, are positively charged by absorbing hydrogen ion in zinc electrolyte, and deposited on the cathode with zinc by the electrophoresis, but this hydrogenion is exchanged by the presence of manganese dioxide particle and the deposition of lead peroxide on the cathode is prevented.
Next, the preventive phenomenon to deposit of lead peroxide particle on the cathode was compared with regard to manganese dioxide and ion exchange resins. From this experimental results, it was considered that the properties of manganese dioxide particle has a, selective ion exchange to hydrogen ion on lead peroxide particle.

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The behavior of impurities in magnesium metal produced by the silicothermic process, was described.
At the reduction process, several impurities, such as Fe, Si, Mn, Zn etc., were contained in the deposit metal. Distribution of each element in the deposit was explained. It was found that some parts of manganese and zinc contained in raw materials are distilled, that is, about 2% of Mn and 70% of Zn are included in the deposit.
At the melting process, it was found that the iron crusible and the flux for melting of deposit don'tcontaminate the molten magnesium.
By the distillation through the wire netting filters placed at the hot end of the condenser, high purity magnesium was produced, and its purity was more than 99.98%

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