筆者は今まで行つて来た研究から次のような事を知る事が出来た。
(1) 磁硫鉄鉱の電気比抵抗・熱起電力は各鉱床毎に一定の傾向を有し, またそれらの頻度分布曲線は生成環境との間に或る種の相関性を有しているので, これらの測定から逆に鉱床生成当時の物理化学的環境を或る程度推察する事が出来る。
(2) 単結晶磁硫鉄鉱はすでにP型半導体と報告せられているが多結晶質磁硫鉄鉱もすべてP型に属し, N型のものは認められなかつた。これは磁硫鉄鉱が欠損型固溶体であり, Fe格子点の欠陥を有している事と深く関係しているように考えられる。
(3) 磁硫鉄鉱の熱起電力の温度依存性はいずれの鉱床の試料についても, ほとんど同一の傾向を示し, 0°～200℃で次式で示される曲線となる。
E=αt+βt²
(4) 坑内における熱起電力の分布は各鉱床毎にそれぞれ一定の傾向を有し, 地質学的産状との間にもそれぞれ一定の相関係性が認められた。したがつて1鉱床について系統的なサンプリングを行つてその電気的性質に関する傾向を把握しておけば鉱床生成環境の解明に対する有力な材料となると同時に富鉱帯の探査上にも充分応用出来るものと思う。

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In this paper, the tensile and compressive strength of coal brought from variouscoal mines in our country were measured and their characteristics were explained. Then the results obtained therefrom were compared to those by the cutting resistance. We found an experimenta formula concerning them, comparing it to that of Mr. C. C. HEKPACOB.
It was also made clear that the friability of coal is more suitable and practical method of anticipating the cutting resistance of coal than the strength of coal.

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The author carried out studies, on water spray which is the most familiar for air-borne dust control, and obtained the following results on its effect.
1. The larger the nozzle orifice diameter is, the more sufficient efficiency can beobtained, namely, in the diameter of each 3.0, 2.5, 2.0, and 0.8mm, it has time ratio of 1.0, 1.18, 1.45, 3.27 respectively, under the condition of 3.5kg/cm² of water-pressure to be needed for 70% of dust suppression.
2. Effect differs from the kind of rock, and, generally the sedimentary rocks have higher effect than the ignious rocks, but coals are not so high as compared with other rocks.
3. The bigger the particle size of air-borne dust is, the higher effect is.
4. The higher water pressure is, the higher effect is, and 8kg/cm² of water pressure will do with water quantity of below 1/4 compared with 2.5kg/cm².
5. When wetting-reagent is used, in 1-2 min. of spray effect can be made ranking anion, cation, and nonion. But in 7-10min. of spray, the order of effect is changed to anion, nonin and cation.
6. When wetting-reagent is mixed with water to be used for spray the quantity of water can be reduced by 20-30%.
7. Wetting-reagent makes little difference in the effect on the kind of rock.
8. Effect is lower in 'the fluidity of the air than in the still.

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The author has investigated thoroughly the relation between chemical compositionand physical properties of sphalerite in relation to mineral dressing.
Specific gravity, refractive index, lattice constant, wettability, magnetic susceptibility, electric conductivity and other physical properties were observed for the samples containing varying amount of iron.
It was found that these physical properties and floatability were affected by the change of iron content in sphalerite.
The main results obtained are as follows:-
(1) Range of iron contentfor twelve samples of sphalerite crystals showed 0.22%(Eagle Picher) to 13.67%(Mozumi), and most of them are in the category of the ordinary sphalerite group except Mozumi and Chichibu samples which are in the marmatite group according to their Fe: Zn atomic ratio.
(2) Specific gravity of the sphalerite decreases as its iron content increases.
(3) Prism method was tried for the measurementof refractive index, it was found that the refractive index of each sample is related to its iron content.
(4) Lattice constant, which was obtained by the X-raydiffraction method using Geigerflex, increases with the iron content.
Angle of X-ray reflection is shifted to the smaller angle side when ferrous iron increases in the crystal lattice of ZnS, and the sharpness of the diffraction peak decreases in accordance with the increase of iron content showing diffuse scattering.
(5) Average value of iron content was estimated from the 0, value of many kinds of zinc concentrates and zinc scavenger froth taken from the mill circuits. It was cleared out that the nature of sphalerite crystals in zinc concentrate and scavenger froth are quite different in physical properties with regard to the difference in iron contents.
(6) Floatability of sphalerite decreasesin accordance with the increase of its iron content, and necessary amount of CuSO₄ as the activator increases relatively. Maximum floatability was obtained at pH 7.0-8.0, but the value of after pH moves to the acid side as the iron content increase.
(7) There is a definite relation between wettability and ironcontent.
(8) A study on the state of aggregation of various sphalerites in zinc concentrates was made by means of the Frantz isodynarnic separator.
(9) Results of electrostatic separation were discussed.
(10) Magnetic susceptibility was investigated by means of the magnetic balance. The magnetic susceptibilityof sphalerite increases with increasing isomorphous iron content.
(11) After studying the minor elements accompanying sphalerite, the author has found that Goldschmidt's rule is agreeable.

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Weight change, heat of reaction and oxidizing velocity in roasting of Ni₃S₂, which is the principal constitution of nickel mattes produced by converting operation, decomposition pressure of NiSO₄ and pressure of the mutual reaction between NiSO₄ and Ni₃S₂ were determined. From these results, the roasting mechanism of Ni3S2 was discussed briefly.

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A method of preparing pure thorium metal by electrolysis of ThF₄ in molten NaCl-KCl bath has been worked out. Graphite crucibles with a capacity of 300g salt have been used as the anode and tungsten or graphite rods as the cathode.
Care has been taken especially to the losses of thorium in the bath as related to thetemperature. Temperatures around 700°C have been found preferablein order to get a sufficient fluidity, of the bath without incurring much vaporization losses of thorium halide.
Optimum conditions of electrolysis have beenfound as follows:
Current density at the anode 0.5 to 1.0A/dm²
Current density at the cathode 20A/dm²
Concentration of ThF₄ 5 to 35 per cent by weight
The thorium metal is deposited as a crystalline powder in the salt matrix and is very easy to be washed and recoverd bythe aqueous technique.

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