Coals produced from Ibaragi Coal Field are low grade and these are using as general fuels. The coal nature is fragile and is high frequancy of the spontcineous combustion.
As the geological feature is compartively worse, the underground support which being suffered by the heavy pressure is uneasy to keeping. When reached around S·L 300m, many coal mines had invited the managing infermities, compelled the to the abolition of their mines. Rivising this dificulty, we planed and have being practice the following six items since we located mine office here.
1) to promote the cooperation of management and labor, and to enforce the technical education for foremen. 2) to intensify the face and mechanical mining. 3) to simplify the traffic system, and to study the support. 4) to make the face working conditions more better. 5) to control the quality of coal. 6) to utilize low grade coals.
Then the output per man increased up 2.5 times than the time when started, and at the present the monthly output is 75, 000-80, 000ton. On the other hand, the up-to-date preparation was established. Our untiring efforts on these rationalization both within and without mine and settling a basic stability on business conditions.

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The discharge coefficients in the air ports of the coal pick were measured by the calculation of the pneumatic frictional losses of these.
Frictional coefficients are about 0.74 for both back and fore ports. Frictional coefficients are more than 0.4. If the pneumattic frictional loss is absent, an increase of a thermal efficiency will be lower than 5%, and an increase of effective power will be 18-20%. This fact is considered to be unnegligible.

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Furthermore, the powders of artificial hematite are investigated in connection with the aerophilic charactor previously reported.
They are fairly floatable in a flotation test without collector, however their recovery increases as the addition of xanthate is increased. Xanthate is taken up evidently upon the surfaces. After the immersion in water for a long time, the response of them to xanthate is considerably reduced. They are restored to the former slate by the drying process following the above treatment. The floatability of degassed powders at 150°C in vacua is decreased to some extent.
Then, it is considered that the adsorbed gas phase gives an effect on the floatability of artificial oxide coupled with the surface structure by itself, especially in the presence of the xanthate-type collector.

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A study has been made to ascertain the relation between magnetic property and electric conductivity (reciprocal of electric resistivity) of pyrrhotite when subjected to electrostatic separation.
As previously known, there exists co-relation between magnetic property and floatability of pyrrhotite, but there is no report concerning to the relation between electric conductivity and magnetic property.
So the authors measured electric conductivity by powder method, and magnetic property by magnetic balance, on the samples by electrostatic separation.
The results obtained are as follows:
1) Magnetism of pyrrhotite increases in inverse proportion with its electric conductivity.
2) Electric conductivity of pyrrhotite has been found to be from 10² to 10 mho/cm by powder method.
3) The maximum electric resistivity is found to be at the point where Fe content in pyrrhotite is about 60%(by chemical analysis). At this point, its magnetism is considered to be maximum and flotability minimum.
4) Indicates electrostatic separation of pyrrhotite is more effective when combined with magnetic separation.

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As the author described in the 1st report, it is not the composition of the bath as a whole, but that of the electrolyte arround the cathode surface that determines the quality of nickel to be electrodeposited innickel electrolysis.
The main object of the present study is to determin the optimum range for the electrolytic conditions, by obserning difference between the cathode film solution and the main bath composition.
Results obtained from the present study has more strictly clarified the conditions for good electrodeposition than studies hitherto conducter exclusively on the main bath.
Conclusions were obtained as follows:-
1. A special apparatus was made for sampling some of the electrolyte of similar composition to the cathode film, and the apparatus has been proved to work well.
2. From the results of experiment, optimum conditions that good electrodeposited nickel is obtained, are as follows. Ni⁺⁺ 40g/l, H₃BO₃ 20g/l, Na₂SO₄ 40g/l, pH4.0-5.0, Temp. 50-55°C, C·D 120-150A/m².
3. It is clarified that there is a close correlation between the bath composition and the electrolytic conditions. Therefor, If we wish to increase the current density, it is necessary that both the temperature and the nickel concentration are increased and the pH Value is lowered.
4. From the experiments on the cathode film, it is shown that when good nickel electrodeposition is done the characteristics is as folloms; if the x axis is to show the current density, and the y axis is to show -ΔNi⁺⁺, +ΔpH, edch curve drown is Qlmost a straight line of line gradient, and there is no precipltation of Ni (OH) ₂.
If the above characteristics is not seen it means a bad nickel electrodeposition.

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By using radioactive silver, ¹¹⁰Ag, the mechanism of cupellation was studied. The absorption loss of silver into the cupel in cupellation process was traced when silver amount in the lead button was small, and its distribution in the cupel was also traced. The vaporizing loss was determined directly. The results are as follows:
(1) Silver in the buttons is absorbed and diffused into the cupel with molten litharge according to the distrbution equilibrium of silver between molten lead and litharge in cupellation process.
(2) At the finishing period of cupellation, silver is absobed irregularly in the cupel, This loss is greater in the following cases, when temperature is high, silver amount is low, ratio of gold to silver is small, and the surface condition of cupel is not good.
(3) The vaporizing loss of silver in cupellation is less than 0.06%, being negligible.
(4) In the cupellation process, the loss of (1) is inevitable, so the greatest care should be to taken to eliminate the loss of (2).

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