This paper is concerned with the analytical results of the mine water of the Kamikita and the Tatemato Mine as well as with the experimental results abnut the chemical and physical behaviors of pyrites and chalcopyrites from various localities.
The pH of the water solutions of pyrites varies between 2.5 and 4.5, and it appears that the solution of pyrite of higher temperature origin shows higher pH than that of pyrite of lower temperature origin, independently of the amounts of solved sulphur.
Chalcopyrites are classified into two groups, higher temperature origin and lowerone, from the. chemical behaviors when solved in dilute sulphric acid, and it seems that from the D. T. A. curves the former chalcopyrite is oxidized more easily than the later one.
It is concluded that the characteristics of mine water are influenced not only bythe mineral compositions of the are deposits and their wall rocks, but also by the chemical and physical behaviors of the main ore-forming sulphide minerals.

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The stress conditions for fracture of rock around underground openings have been investigated experimentally as well as theoretically, and it has been found thct tension fracture took place where about a half the stress calculated by the theory of elasticity reached the tensile strength, while compression fracture took place where about 0.95 times the theoretical stress reached the compressive strength.
It is found, therefore, that calculation of stress by the theory of elasticity affords an effective material to foresee possible fracture of rock. Further it is shown that the state of stress around underground openings is, to some extent, inferred by investigating whether or not fractures occur around them, and if any, how they are.

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Along with the increased addition of frother, the self-air-inhaling capacity will decrease.The phenomenon like this is simply supposed to be due to the fact that in proportion to the breaking up of air bubbles into smaller ones, the speed at which they come off the agitating zone will get lowet, and nc other reason is not known yet in detail.
Standing on the view-point above, the author measured the flow patterns and the state of dispersion of bubbles within the pulp in the cell to make clear the relationship of them with the introduced air quantity under the same experimental condition with varying number of baffle plate and obtained the following results:-
1) The state of dispersion of air bubbles in the cell is depended considerably upon the flow-patterns, within the pulp, provided with the same condition, the self-air-inhaling capacity beiog varied in accordance with the change of the state of dispersion above.
2) The pulp, first forming the up-rising flow with rotation along the cell-wall and approaching the cell-corners, then rolling back, and take the form of down-falling flow with rotation around the external surface of the stand pipe.
3) The displacing speed of bubbles up-rising along the external surface of the hood will not only be affected by the down-falling flow, but minuter air-bubbles rising up along the cellwall, will, without coming up to the water surface, be rolled back into the down-falling flow.Accordingly, the vertical motion of both up and down flows being large, the smaller the air bubbles are, will the quantity of bubbles of air staying around the external surface of the hood become the larger.
4) The more the quantity of air-bubbles staying around the external surface of the hood, will the more quantity of air-bubbles be reinhaled by the impeller, the faculty of the impeller inhalina the open air being lowered.(Cf.foregoing reports of the author)
5) Along with the increase of the number of baffle plates, since not only the rotating flow will be. disturbed but the up-rising flow will be homogenized and its velocity be lowered, the down-falling flow too will become non-significant.
Accordingly the air-bubbles will be uniformly dispersed with the decrease of the quantity of them staying around the external surface of the hood.

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In order to recover the coal concentrates of low ash content, the electrostatic separation of coal in corona field was investigated by the Huff separator.
From the experiments of the coal separation by the Huff separator in corona field, it is recognized that the coal particles which are extremely low in ash content are attracted to the surface of grounded roller, while the coal of high ash content is repelled from the roller. It is more successful in corona field to recover the coal concentrates of low ash content than in the field without corona discharge.
From the measurements of conductivity of coal and electric charge of coal particles acquired in a electric field, the relation between conductivity and ash content was clarified. Furthermore, the mechanism of coal separation in a corona field was considered.

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