The specimens of “Iwwaki” sandstone brought from the Joban Colliery were used in this experiment. Each specimen, formed rectangular prism, was loaded at the penter point of its span riding on two knife edges, and after the loading the ancount of the deflection was observed during 300 hrs.
Then one of the main results obtained was as follows.
Although the stress was not reached to the max. stress equivalent to the bending strength but nearly closed to it, say 80% or over, the breakage happened within 300 hrs, if the loading was continued.
And the author tried to introduce the consideration as a relaxation phenomena for this study.

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The oxidation of coal has been determined under absorption of oxygen at various temperatures less than 100°C.
It may be confirmed that oxidizing reaction of Coal depends upon the absorption of oxygen.
The rate of oxidizing reaction was measured with the amount of oxygen which disappeared from the gas phase in a definite time.
The inter-action of oxygen with coal will take place on its surface, so that the rate of oxygen consumption will rise rapidly with increasing of the surface area per unit wieght of coal, -being determined by testing of the various kinds of coal, which ralation is shown with the formula (1). The value of “a” in the text depends upon the kind of coal to be tested. The above results obtained have been already confirmed by T. F. Winmill, who examined on foreign coals.
The rate of oxygen consumption rises with increasing the temperature from 30°C to 100°C, which relation may be expressed with formula (2). Besides, it will be affected by various factors which have relation with physical or chemical properties of coal, such as decomposition and ignition temperature, coalification degree, pH of gas oil of coal, and so on.

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In the former reports, analysing the molecular structure of both the typical hydrophobic minerals (natural floaters) and hydrophilic minerals, the author extracted a characteristic common to each group; covalent bond and Van der Waals (London) bond to the hydrophobic and electrostatic bond to the hydrophilic. And on the basis of this, the mechanism of wettability was deduced.(1) The hydrophobic mineral surface have the Van der Waals (London) force field, that is, the dispersion force field, where as the hydrophilic surface have the electrostatic field.(2) As the dispersion force field may be replaced by the high (ultra-violet) oscillating electric field, there is no interaction between the dispersion force field and. the electrostatic field ; this leads to “non-wettable”. But there exist the distinct interactions between the hyd-rophobic mineral surface and non-polar liquid; the dispersion force, and between the hydrophilic mineral and polar-liquid; the electrostatic force. These lead to “wettable”.
This report gives the following supplements on Wettability.
(1) Though the Weyl's theory on wettability is different from the.author's, these two have, in a sense, the close connection with each other.
(2) As one of the application of the author's theory, it was tried to explain the mechanism of emulsifiers for the type of emulsion (water in oil or oil in water type).
(3) In the flotation. tests of talc and pyrophillite, it was shown that there was the distinct correspondence between changes of crystal structure by heating and floatability (wettability).
Considering the mechanism of wettability as mentioned above, the attachment of bubble to hydrophobic mineral in flotation is smoothly explicable through the dispersion force, which will be discussed in the next report.

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In hydrometallurgy, the small quantity of soluble metal salt present in raw material is leached continuously by thickener or drag belt in some cases. In such cases, several formulae can be introduced, and with them the metal concentration of leaching solution or washing solution and leaching efficiency can be determined. These formulae were applied to some cases of continuous leaching of copper from pyrite cinder. Following results were obtained.
1. When leaching tank alone or a series of one leaching tank and one washing tank were used, metal concentration of solution and leaching efficiency approached infinitely a limiting value in the course of time. This limiting value was determined by the content of soluble metal salt in raw material and the content of solution in leached residue after leaching or washing. In these cases, increasing rate of metal concentration of solution and decreasing rate of leaching efficiency decreased when capacity of tanks increased.
2. When a leaching tank, a washing tank and a recovering tank were operated simultaneously, metal concentration of solution and leaching efficiency were determined by the content of soluble metal salt in raw material, the content of solution in leached residue after leaching or washing and the quantity of solution which was let to flow from leaching tank to recovering tank

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