The drift driving is most popular in mines, and yet it depends mostly upon the worker's experienceand art. So is the operation of blasting in spite of its abundance and colorfulness of basic theories.
The author's study is, therfore, aimed at setting up criteria for practical uses as inscribed on theface. It is summarized as follows:
1) Two groups of formulae and ready charts are proposed. The first group which was based on theidea of equi-burden distribution, was to estimate normal number of drill holes or their distribution.
The second was to caiuculate explosives and it was geometrically composed from the cubic theoryconcerning concentric charge.
2) The characteristics of blasting factor of slot cut varing with its aperture angle, were investigated.Also established was a method to estimate the blasting factor at a desired angle from given factorsat any angles.
3) It has become clear that the blasting factor can't be taken as constant value
4) The center cut tests were resulted in finding that an adoption of poly-hole pattern rather thanfew-hole one and separate time firing was most preferable with more efficiency and less failure.
Accordingly it can be said a conventional type of crate. test with single hole is inadequate in moustcases.

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Collapse or dislocation of refuse heap results in catastrophe especially in Kyushu. Prevention ofdisasters is urgent problem and Fukuoka mine safety bureau plans this year to examine safety of refuseheap and prevents disasters. About 10 years ago, this bureau has examined already safety of many refuseheaps in Kyushu and analysed mechanism of dislocation.
According to the report of bureau, the most important and essential factor which has influence ondislocation is ground water. But it is difficult and costly to know water level in refuse heap exactly. The report described it was impossible to get water level curve in refuse heap.
But this is not impossible and the author showed in this paper the method of calculcition to get thewater level. This method is not completely theoretidal and it is necessary to make boring at least three, in special case it is enough only one. With data of these boring, we can calculate the water levelat any places and get the water level curve in refuse heap.

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The preceding article (2nd Report) referred to the relationship between the characteristics of fracturesurface and the electrochemical properties of aluminum-silicate minerals such as kyanite, andalusites.and sillimanite. It was also presented in the first report of this investigation that the results of flotationtests of kyanite and andalusite out of the above three minerals were correlated with those electrochemicalproperties.
Kyanite has a triclinic crystal structure, -whereas both andalusite and sillimanite have an orthorhombicstructure. However, since these three minerals are known to have identical chemical compositions (Al₂O₃·SiO₂), it appears desirable to undertake a supplementary study on the flotation characteristics ofsillimanite in order to confirm the effect of the crystal structure on the surface properties and floatabilityof the above-mentioned aluminum-silicate minerals.
In this paper the findings on the flotation characteristics of sillimanite are summarized and theresults compared with those obtained for kyanite and andalusite. As a result of batch flotation tests onquartz-sillimanite mixtures, the selectivity index reached maximum at about pH 3.0 when sodium dodecylsulfateis used as a collector, indicating that the floatability of the mineral depends mainly on its electrochemicalproperties. It is further suggested from the results of flotation tests using oleic acid as a collectorthat either the flotation of quartz with calcium activation at about pH 11.0, or the flotation of sillmanitewithout activation at the pH range of 6.0-7.0 is preferable.

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In order to clarify the dissolution mechanism of zinc-ferrite, the effects of the cooling rate, Fe₂O₃/ZnO ratio, and the formation atmosphere on the dissolution rate were investigated.
In the present experiments, the following results were obtained.
(1) The zinc-ferrite formed at 1000°C has the same intrinsic dissolution rate k (g·min^-1·m^-2) irrespective of the cooling rate. The dissolution rate of that formed above 1100°C, depends on the coolingrate and, if cooled rapidly, the rate increases considerably, whereas, if cooled slowly, the rate remainsto. be much the same as thas of 1000°C.
(2) If excess Fe₂O₃ is present in zinc-ferrite in solid solution, the intrinsic dissolution ratedecreases and the more Fe₂O₃ in zinc-ferrite, the smaller is the dissolution rate. The rate increases againif Fe₂O₃ is precipitated during slow cooling.
(3) If the zinc-ferrite formed at 1200°C is heated in vacuum at 1000°C, the intrinsic dissolutionrate increases considerably, while, if heated in air at 1000°C, the rate becomes almost the same value asthat of the zinc-ferrite originally formed at 1000°C.
From these results, it can be concluded that the zinc-ferrite of 0^2-deficient composition dissolvesin dilute sulfuric acid more rapidly than that of stoichiometric composition, and that therefore the dissolutionof zinc-ferrite-is initiated from the anion vacancy sites and the rate is controlled by the concentrationof anion vacancies.

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NbO₂ was prepared by heating Nb₂O₅ in the stream of hydrogen. It was usualy produced at temperatureabove 1, 200°C.
NbO was prepared by heating the mixture of Nb₂O₅/Nb (mol. ratio) =1/3 or NbO₂/Nb=1/1 at about1, 000°C in vacuum.
NbC was prepared by heating the mixture of Nb₂O₅/C (mol. ratio)=1/7 at about 1, 400°C.
Reactivity of NbO₂, NbO and NbC in chlorine atmosphere was studied by means of the thermobalanceand boat testing.
The results obtained were as follows
(1) Reaction between NbO, and Cl₂ begins at about 250°C, the condensato was NbCl₅ and theremainder was Nb₂O₅.
(2) NbOCl₃ is produced by heating NbO in Cl₂ atmosphere.
(3) When NbC reacts with chlorine, NbCl₅ sublimates and carbon remains.

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In this paper the author presents an idea of “the coal mine in CO₂ atmosphere” and considers someproblems to realize this idea.
The mine safety is one of the most important problems in coal mine from the view point of humanityas well as engineering. Up to the present, all of the efforts to protect the mine explosion have been attemptedand succeeded only to minimized the probability of mine explosion.
So long as there are oxygen, fire damp and some sources of fire, such as spontaneous combustielectric spark, heat of friction, and so on, the probability of mine explosion could be minimized to beon I y a fraction of many thousands but not to be zero. In order to make this probability zero, there isthe only way to reduce either one of above three factors of mine explosion.
Since it is impossible to reduce fire damp and some source of fire, we need to reduce oxygen orair. This is the reason why the author proposes to replace the mine air by CO₂, and realize “the coalmine in CO₂ atmosphere.”
In the coal mine in CO₂ atmosphere, the applications of all equipments and installations are permittedwithout explosion protective devices. This would accelerate the automation and mechanization ofcoal mine operations, in turn the automation and mechanization would accelerate the realization of thecoal mine in CO₂ atmosphere.
There would be, of cource, many problems and difficulties to be solved in the way to realize thecoal mine in CO₂ atmosphere. Some of these problems to be researched are as follows;(1) the heat exchange or cooling of CO₂ atmosphere,
(2) the improvement of the capacity of oxygen mask,
(3) the use of vapour pressure of CO₂ as the power source of rock drills and coal picks,
(4) the consumption and supply of CO₂, and
(5) the communications between miners.
But these problems seem to be not so difficult that we are disouraged to realize the coal mine in CO₂atmosphere.

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