Recently, ANFO explesive has come into use in metal mines and quarries for reasons of its economical profit and safety.
It has been found out that ANFO explosive has scarcely shown the differences in blasting effects in comparison with conventional explosives, for example Kiri dynamites and carlits.
The detonation'; characteristics of ANFO explosives that need to carry out the designs for blasting has been studied by several workers, but it has not been clari fied sufficiently.
The authors measured the detonation velocity of ANFO explesives with ion gap method and obtained the results as follows.
1) Under fixed detonating conditions, the final detonation velocities of ANFO explosive are hardly dependent on the kinds and quantities of primers used.
2) The quantities of primers, in other words, the differences in priming energies exert an influences upon the time up to the fixed detonation velocities.
3) Under the same detonation conditions, the optimum quantity of primer can be calculated from the blasting models used.

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In this study, at first, the behaviour of the rarefaction wave by which the tensile stress in the material is considered to be relaxed has been studied. The main results obtained are as follows:
1) Measured value of the propagation velocity of the rarefaction wave mentioned above agrees with that of the longitudinal wave in the material.
2) The tensile stress at a point in the material has been relaxed linearly by the rarefaction wave within about 10-20μsec after the wave has arrived at the point.
Through the discussion of the effect of the guide hole on the stress distribution in the material, it is clarified that the tangential tensile stress produced in the direction of the guide hole attains to greater value earlier than those produced in the other directions.It means that the crack towards the guide hole can be produced ahead of all other radial ones and its length might be the longest. As the rarefaction waves are projected from the surface of the crack in the direction of the guide hole into the material, the hoop stress in the material has been relaxed from the position of the crack. Therefore, no other radial cracks extend near the direction of the guide hole.And also, it is clarified that the effect to check the extension of radial cracks by the guide hole appears more effectively with decrease of the distance between the charge hole and the guide hole.
Lastly, a field experiment was carried out to confirm the results of the small scale experiments which were performed in the laboratory by using a polymethyl methacrylate, and it was shown that the results obtained in the field agreed fairly well with those obtained in the laboratory.

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The extent which was able to suck up thin placer on the seafloor by a straight suction pipe was limited with comparing that a large volume rate of flow was required. Then the flanged suction pipe was made use so as to enlarge the extent being able to suck up thin placer.
The object of this study is to obtain the basic information concerned with how much extent of thin placer lying on the horizontal seafloor can be sucked up by flanged suction pipe.
The basic relation on dredging of thin placer by the flanged suction pipe was semi-theoretically induced and the experiments were carried out in the small sized models so as to make sure the induced relation.
The obtained relation is expressed by the formula
Q/A {ν(ρs/ρ-1) g}^1/3=K
where
A: the cross-sectional area of flow between flange and floor, but in circular flange, the contraction cross section at circumference of flange
K: the constant determined by the experiments
Q: the flow rate in the suction pipe
ν: the kinetic viscosity of water
ρs, ρ: the density of placer, and of water respectively
In this experiment the value of K equals to about 14.

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Generally the grinding of ore for mineral separation is conducted as aiming liberation. However, the ore consisting of various minerals is very difficult to grind ideally, for liberation size and grindability of composing minerals do not give always the same value. Especially it is required to avoid overgrinding of heavy minerals, e. g. cassiterite, sheelite, etc, when gravity separation is applied in the process.
On the ore composing of pyrrhotite, marmatite, galena, cassiterite, chalcopyrite, calcite and quartz, we conducted mill grinding on the laboratory scale and investigated size distribution of these minerals in the products.
The results obtained are as follows.
(1) Product with the ball milling shows a tendency that cassiterite remains at a size coarser than sulfide minerals.
(2) In the rod milling both cassiterite and sulfide minerals are ground to the almost same size.
Thus the authors recognized that the ball mill possesses more suitable character than rod mill for selective grinding of the complex sulfide ore containing cassiterite, i, e. cassiterite at coarse size and sulfide minerals at fine size.

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Thermodynamics of the copper mattes in the FeS-PbS system and Cu₂S-PbS-FeS system were studied in the temperature range from 1200°C to 1250°C
The vapor pressures of PbS at various compositions of these mattes were measured by the dew point method and from these experimental data thermodynamic functions were calculated.
In the FeS-PbS system, activity curves of PbS deviated positively from Raoult's law and those of FeS deviated positively or negatively from Raoult's law depending upon the composition of the system.
The degree of deviation was represented by activity coefficient γ and the values of γ were 1-1.3 for PbS and 0.9-1.5 for FeS.
Also by using these activity data, free energy, enthalpy and entropy of mixing and chemical potentials of PbS and FeS in the FeS-PbS system were obtained.
From activity measurements of PbS in the mattes of Cu2S-PbS-FeS system at 1200°C, iso-activity curve of PbS in the Cu₂S-PbS-FeS system at 1200°C was made.

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The comparison of zinc fuming rates between copper converter and lead-zinc blast furnace slags, the influence of CaO or FeO content of the slag on the zinc fuming rate and the effect of fuming gas composition on the yields of matte and metal were examined by introducing CO-CO₂ gas mixtures or N₂ gas into the molten slag at the temperatures of 1220°C and 1280°C.
The zinc fuming rate of the converter slag was lower than that of the lead-zinc blast furnace slag.It is probably due to the reduction of magnetite present in the converter slag together with the reduction of zinc oxide, especially at the beginning-of the time of slag fuming.The zinc fuming rate was increased by adding CaO to the slag in the range of 1-20% CaO.But the effect of the FeO contents of 30% and 45% of the slag, keeping the CaO%/SiO₂% ratio constant, on the zinc fuming rate was not apparent.The quantities of matte and metal separated from the slag increased with the increase of CO content in the fuming gas.

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