Preliminary petrographical and mineralogical investigations of so called “Chiyoda bota” associated with the coal beds of the Onga formation, Ôtsuji group (Palaeogene) at the Takamatsu coal mine in the Chikuho coal-field are presented. The results of x-ray powder analyses as well as chemical, petrographical and differential thermal investigations the minerals and clay materials separated from them show that the shales are composed of halloysite with very low crystallinity and a small amounts of illite, quartz, feldspar, etc.

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This study is a part of series which is carried on with the hope that if they can clear controversial question, i. e., mechanism of rotary and percussive drilling, and can get some idea needed when we come to choice between rotary and percussive drilling for particular rock formation.
Special test apparatus was designed for studies on indentation of bit under dynamic force.
This comprises of mechanical part, anvil, hammer and bit, and electronic measurering apparatus.
Indentation depth of bit and dynamic force on bit are measured by means of electric capacitance and wire strain gage respectively which are displayed on the dual beam Braun tube oscillogragh.
Instrument used for static test is conventional Brinell hardness tester except ball which is replaced by test bit.
Caluculating dynamic and static energy, needed to get certain depth of penetration, from the force and penetration measured, it is known that fewer energy is necessary to get same penetration, if dynamic force is applied, compared with static force for hard rock formation, and vice versa for soft rock formation.
Although authors must admit that there are various other factors, this result implies big suggession for us to chose between rotary and percussive drilling for certain rock formation to get more hole for cost.

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Some concepts concerning stresses in rock around an underground workings have been proposed by some reseaschers. However, such concepts depend on theoretical considerations and on results of loads acting on underground supports near workings.
To realize stress distribution in coal-seam or rock near workings, the author has made loadcells which are fixed by wire straing gauges, and a strain meter which is convenient for use underground. Structure, sensitivity and other characteristics of the load-cell and strain meter are illustrated.
To measure the stress variation in a coal-seam, a load-cell is pushed in a bore hole drilled in the coal-seam. The clearance between the cell and the wall interior is filled up by cement milk.
After the cement milk has solidified, the resistance variation of the wire strain gauges caused by the stress variation in the coal-seam is measured by the strain meter.
Fig. 1 shows the structure of the load-cell. An active gauge is fixed on the A-surface and a dummy gauge is fixed on the D-surface. Fig. 2 shows the sensitivity of the load-cell buried in a cement mortar column. Fig. 5 is a circuit of the strain meter used. Fig. 8 and 12 both illustrate the site of a longwall and tee location of a load-cell buried in a coal-seam at the beginning of measurement at the Yoshima Coal Mine. Fig. 10 and 13 are the data obtained. Fig. 11 and 14 show the relation between the stress variation in the coal-seam and the distance from the longwall to the location of the load-cell.
According to the results obtaind, one can realize that Fig. 11 is somewhat similar to the concept of stress in a coal-seam advanced by W. Haack and Fig. 14 is similar to the concept suggested by F. Spruth.

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Sinplified method for determination of free silica in airborn dust in mine atmosphere is suggested in this report. This is to say, the fundamental study on the microscopic method for determination of free silica content in samples on the deck glass collected by the Jet Dust Counter applying the phosphoric acid method is reported in this paper.
This method has following merits:-
1) This method is simple and practical.
2) Less time and labours will be necessary for sampling.
3) Contents of free silica in very fine and injurious dust can be determined.
4) Direct relations between several mine works and free silica content in mine dust can be quested.
5) Free silica content can be shown by the percentage of number of particles, so from point of prevention for Silicosis, this is a very significant method.

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The theoretical explanation of the performance about a single roll-type electro-static separator has not been made public in a satisfactory manner, because of many difficult factors inherent to the characteristics of the apparatus, although they are very important.
These factors, for instance, are those:-such as the speed of roll, the fineness of mineral particle, the polarity of applied voltage, the angle of charged electrode to the roll, the clearance between the aboves, the magnitude of applied voltage and the electric field intensity on the roll surface.
So the effects of the above factors were investigated to determine the optimum condition for separation.
The principal results of analysis using this experimental separator are as follows:-
1) The optimum roll speed selected is approximately 80 revolutions per minute.
2) The fineness of mineral particle should be greater than 150 mesh.
3) The optimum angle of charged electrode to the roll is 45 degree for a good conductive mineral, and smaller than 45 degree for a poor conductor.
4) The repelling distance to the meridian of weight distribution can be seen as a exponential function.

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Sphalerite used in this investigation was handsorted from large crystalline mass obtained from Mitate Mine, Yamagata. Analyses of principal elements were as follows: Zn 63.60 pct; Fe 1.40 pct; Cu 0.09 pct; Pb trace; Mn 0.02 pet; Cd 0.30 pet; S 32.77 pet; Si0₂ 0.40 pct.
The amounts of abstraction of xanthates were calculated from xanthate ion concentrations in solution before and after contact with the powdered samples. Xanthate ion concentrations were measured by counting the activity of S 35 labelled potassium ethyl xanthate (KEtX) in some experiments and by spectrophotometric method using 301mμ wave length in others.
From the experimental work the following results were obtained:
(1) The amount of KEtX adsorbed was extremely small as compared with copper-activated sphalerite and was almost nil at high pH value of solutions.
(2) The amount of KEtX adsorbed increased by addition of Zn ion in the solution. This phenomenon can be interpreted by theory of “common ion activation”.
(3) Also, adsorption exieriments were carried out with the higher alcohol xanthates such as butyl, amyl and hexyl xanthate. As a result, it was confirmed that adsorption of these xanthates had a correlation with solubility of their zinc xanthates, i. e., a potassium xanthate of which zinc xanthate has low solubility was more adsorbed than the others of which zinc xanthates have higher solubility, or vice versa.
Measuring solubility of the above zinc xanthates by different methods such as radiotracer technique using Zn 65 marked zinc xanthate, ultraviolet spectro-photometric method for xanthate ion, colorimetric determination of Zn using dithizone and polarography for Zn, the respective values obtainedwere fairly coincident. The value of solubility of zinc ethyl xanthate was found to be in the range from 1.215×10^-3mol per 1 to 1.020×10^-3mol per 1 at 25°C.

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The properties of the oxidation products of pyrite, above all, the composition of FeS_1+x formed at the intermediate stage of the oxidation and the conditions of formation of Fe₃O₄, were investigated by the methods of measurement of the relative intensity of magnetization, thermomagnetic analysis, and X-ray. Results obtained were summarized as follows;
(1) The intensity of magnetization of the products increases along the oxidation, reaching at its; maximum value in its way, and after then, it dereases. In the atmosphere whose partial pressure of oxygen is 0.01 atm., this maximum value is remarkably higher than that of the oxidation products, which were formed in the atmosphere whose partial pressure of oxygen is above 0.01 atm.
(2) This maximum of the intensity of magnetization was found, by thermomagnetic analysis and X-ray measurement, to be caused mainly by the formation of Fe₃O₄. In the oxidation in the atmosphere whose partial pressure of oxygen is 0.01 atm., it was found that Fe₃O₄ was stable just to the end of the oxidation and Fe₂O₃ was formed abruptly at the end of the oxidation. On the contrary, in the atmosphere of more than 0.03 atm. of oxygen, Fe₂O3 and small amount of Fe₃O₄ was found, to be formed at the comparatively initial stage of the reaction.
(3) FeS_1+x formed at the intermediate stage of the oxidation was certified as a ferromagnetic one, and its composition is near the upper limit of solubility of sulphur in FeS_1+x.
(4) From above-mentioned results of studies, the mechanism of the oxidation in a layer of fineparticles of pyrite was considered. According to Niwa and Tohata, the oxidation in the layer of fine: particles of pyrite proceeds from the surface towards the interior. Therefore, the partial pressure of oxygen decreases along this way and the layers of the oxidation products after the thermal decmposition are arranged from the surface as follows; Fe₂O₃, Fe₃O₄, FeS_1+x. From the results of (1) and (2), it may be said that in the oxidation at low partial pressure of oxygen in the atmosphere, among, these layers of oxidation products, the Fe₃0₄ layer becomes much thicker in the intermediate stage of the reaction.

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The electrical conductivity of organic solutions of UCl₄, has been measured using the waterfree solvents like Methanol, Ethanol, Acetone, Acetonitrile, Formic acid, Acetic acid, Methyl acetate, Ethyl acetate, Ethyl benzoate, Pyridine.
The results indicate that the solution of Methanol, Ethanol, etc, which are high in dielectric constant, seem to have enough electrical conductivity to run the electrolysis.

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