In order to investigate the mechanism of the rock blasting, it is considered to be very important to know the amount of pressure produced on the inner surface of the charge hole by the.detonation of an explosive. Therefore, by means of observing the stress wave produced within a steel rod by the detonation of an explosive which was placed in contact with this rod in a charge hole, the amount of the peak pressure acted on the inner surface of the charge hole was estimated and the state of rise and fall of the pressure with time was measured.
As the principal results of the present experiments, it was found that the detonation pressure was mostly influenced by the variation of the detonation velocity which was controlled by the effect of confinement and the detonation pressure of the confined 45 grams of No.3 Take Dynamite attained 1.5 times as large as that of the same explosive fire' freely in air and also that the duration time of such detonation pressure in a charge hole ranged from about half a millisecond up to several milliseconds.

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The purpose of this study is the investigation of the spontaneous ignition phenomenon in the wet coal pile by using the special furnace.
The experiments yield the following results.
1) If the ventilation passes by the ignition source, there exists the definite relation between the temperature directly measured at the exhaust of the wet coal pile and the temperature of the ignition source. Thus, calculating the entalpy of air at the observing point, we can anticipate the condition as well as the temperature of the ignition source.
2) In the case of the wet coal pile, the heat created by the spontaneous ignition is absorbed by the moisture in the vapour saturated air so as to keep the temperature of the wet coal pile lower and to delay the propagation of the high temperature region from the ignition source. Therefore, we can say the wet condition of the coal pile is desirable in order to prevent the spontaneous ignition.
3) However, if the spontaneous ignition occurs in the wet coal pile, it takes longer time to cool it down by sealing because the vapour in the air has excess entalpy, which stores more heat, than the dry pile.

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We have measured by the bending test the bending stress of wire ropes, which has now been discussed for about a century. As the results of the experiment, we have concluded following:
1) Not only each wire in a wire rope slips along each other, but also the section of the ropeis deformed in accordance with its bending.
2) The value of bending stress is not the same at different parts of the section of the rope, but it shows variation at each part of the section. The variation seems to be caused by the separation and deformation of the section.
3) We have found that the value of bending stress hitherto measured and considered the maximum is not the largest, but ather the minimum or one of the smallest values.
4) The modulus of elasticity for bending stress E_b amount to nearly 20, 000kg/mm² for maximum bending stress in our experiment.
Our conclusion is that we should adopt E_b=20, 000kg/mm² instead of E_b=10, 000kg/mm², which is adopted in the regulation for safety of, mining in our country.

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As a convenient measurement of ferromagnetism the powder method have been used for valuations of various magnetic minerals.
In the method total magnetic flux is measured by ballistic galvanometer using filled powder in nonmagnetic cylindrical tube instead of usual bar shaped specimen. However in the method as the demagnetizing factor have never been solved, magnetization curve, i. e. variation of intensity of magnetization against effective magnetic field can not be obtained, only shared curve, i. e. variation of intensity of magnetization against external magnetic field is obtained on the supposition that the demagnetizing factor equals to zero.
In order to extend the method so as to be able to obtain magnetization curve directly from this measurement, the author experimentally decided the demagnetizing factor by using bar shaped and powdered. magnetite.
The results obtained are summarized as follows
(1) In the region of initial permeability the demagnetizing factor takes the value of about 0.9
(2) It seems to take the values of ranging from 0.92 0.95 to in the region of reversal process.
(3) In the region of continuous rotation it gradually decreases with the increase of intensity of ma gnetization.
These results may have fundamental importance in utilization of the above method.

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An aqueous pulp of the complex sulphide concentrates (-200mesh) having a content of 10.6 pct Cu, 20.5 pct Zn, 20.9 pct Fe and 34.7 pct S was treated with oxygen at elevated temperatures and pressures.
99 pct of zinc and 95 pct of copper in concentrates were extracted under the following conditions. pulp density; 10.7 pct solid leaching time: 1 hr temperature: 185°C total pressure: 40 atm.
99 pct of zinc and 90 pct of copper were leached at 170°C, under 20 atm in 4 hrs.
At a temperature of 185°C and a total pressure of 40 atm, pulp density and leaching time were varied as follows: pulp density: 10.7 to 24.2 pct solid (30 to 80 g in 250 cc water) leaching time: 1 to 5 hrs.
More than 95 pct of zinc in concentrates were always leached under these conditions, and 90 pct of copper were extracted when the pulp density is 24.2 pct solid and reaction time is 4 hrs.
The more the amount of iron were leached, the higher the pulp density became, but these were not affected by the leaching time.

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The purpose of this research is to concentrate titanium by magnetic separation of hematite from the low grade titanium concentrate making use of the relations between the magnetic properties and magnetizing or oxidizing roasting, and to study the reactivities of these high grade titanium concentrates with sulphuric acid in order to use them as raw materials in the pigment industry.
Following results were obtained.
1) Hematite mixed in the low grade concentrate was easily converted to magnetite by gas reduction. The optimum condition was to reduce it with less than 10% CO gas at 600°-700°C. After reduction titanium was enriched from 32% to 39% TiO₂in the non-magnetic portion by magnetic separation. The titanium recovery was 88% and the iron removal was 42-45%. The same results were obtained by fluiding reduction.
2) Ilmenite could become ferromagnetic substance by oxidizing roasting at 700°-750°C for half an hour and was concentrated in the magnetic portion. Titanium could be enriched to about the same content as in magnetizing roasting, but the titanium recovery and the iron removal were less than that.
3) On the contrary to the high reactivities of the titanium concentrate by magnetizing roasting with both 70% and 93% H₂SO₄, the reactivities of the one by oxidizing roasting were very low with both acids due to the convertion from ilmenite to Fe₂O₃·TiO₂ and rutile. From the iron separation and the reactivity with sulphuric acid, magnetizing roasting seems to be superior to oxidizing roasting.

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Usually, the lime sulfur (calcimum polysulfide) which is an excellent fungicide is produced from the refined sulfur and the calcium oxide. The principle of this reaction is similar to that of the sulfur ore treatment with super heated steam in an autoclave. We, then tried to prepare the lime sulfur directly from the sulfur ore treating it with calcium oxide milk in an autoclave.
And we found that the lime sulfur could be successfully produced from sulfur ores by treating them with calcium oxide at the following conditions; ore size, ca. 13 mesh. Mole ratio of CaO: S=3.0: 11.5. Temp. 105-110°C. Reac. time 20-40 min. Agitation 200rpm.
When the sulfur ore contains about 73.0% or more of sulfur, this method was applicable more economically than the usual method with better, recovery regardless of origin and kind of the ore. We have constructed the factory by this method, and confirmed the results mentioned above.

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