Thiobacillus ferrooxidans, a chemoautotroph using iron oxidation as an energy source for growth, is attracting the interesti n its role in leaching of sulfide minerals.
Many studies on this bacterium have been performed principally in the ecological aspects for over 30 years since the discovery of it. From the results of these studies, more research works regarding following subjects will be necessary for the further progress of the bacterial leaching.
1) Establishment of the suitable environment for the bacterial action.
2) Discovery of more effbctive species or improvement of strains.
3) Development of effective combination with other unit operationsuch as flotation and agglomeration

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This paper discusses the theoretical treatment of rock deformability by using the crack model.
In the present analysis, discontinuities in rock are assumed to be represented by elliptic-plate-cracks. Two crack cases are analyzed, one is open crack and the other is closed crack.
Expressions for effective compliances of material with a single isolated crack are given as shown in eq.(6) and eq.(15). The effective elastic moduli of material with randum oriented cracks are analyzed by using the self consistent method and expressions for them are shown in eq.(17), eq.(19) and eq.(20).
For an application of this theory, the relationship between the rock elasticity and Rock Quality Designation are discussed.
In estimating rock deformability, the density ratio of open-cracks to closed crack shares the important role with other factors, namely, the total crack density, the crack geometry and the frictional coefficient.

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Main part of the permissible test of electric detonators for use in coal mine is aimed at safety tests against methane ignition. However, safety properties of electric detonators against coal dust are also important both for safe blasting at coal mines and safe operation in pulverized coal combustion furnaces at power plants and others in case of containing of miss-fired detonators.
Several series of safety tests of electric detonators against methane and coal dust were carried out varying temperatures from room temperature to 150°C. Results are briefly summarized as follows.
1. Spark particles generated from copper-cell detonators is less than those from iron-cell detonators. On the other hands, flame of copper-cell detonators is larger than that of iron-cell detonators and then, it is liable to ignite methane or coal dust in case of copper-cell.
2. When temperature is increased up to 150°C, safety degree of detonators against coal dust decreases considerably.
3. Ignition of coal dust or methane by detonators depends on the flame rather than the spark particles during the initiation of detonators.

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In order to examine the behavior of particles for the heterogeneous flow with a moving bed, several investigations are made experimentally. From photographs taken for the behavior of particles, the particle velocity and the height of the moving bed are measured. It is found that the height of the moving bed decreases as the mean fluid velocity increases, and it is not affected by the variation of the pipe diameter and solid particle concentration by volume. Furthermore, it is ascertained that the moving bed velocity is expressed as the empirical equation (5).
Fluid velocity profile is measured by a pitot tube, and it is found that the mean fluid velocity in the moving bed is approximately equal to the moving bed velocity.
From particle velocity profile and fluid velocity profile, the ratio of particle velocity to that of fluid is obtained in the moving bed region and the suspension region.

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As a fundamental study on utilization of microorganisms in the differential flotation of sulfide minerals, effects of oxidation by an iron-oxidizing bacterium (Thiobacillus ferrooxidans) on floatability of pyrite were investigated. In addition, some surface properties of oxidized pyrite were investigated in relation to the floatability.
The main results obtained are summarized as follows:
1) Bacterial oxidation and leaching behaviors of pyrite are much affected with the condition of previous culture of the bacterium. The previous culture using pyrite substrate reduces induction period for the oxidation.
2) Floatability of pyrite is remarkably depressed by bacterial pretreatment. The decrease in the floatability well corresponds to the degree of progress in the leaching based on the condition of previous culture.
3) The surface of pyrite changes into porous structure with the progress of bacterial leaching, while a notable decrease in the floatability of it begins before. Accordingly, in this case, it is apparent that the effect of surface structure on depression of the floatability of pyrite is not dominant.
4) By the bacterial oxidation, jarosite or a jarosite-like insoluble sulfate is formed on pyrite surface and wettability of the pyrite becomes larger. Consequently, it is inferred that the depression of the floatability mentioned above is due to the formation of a hydrophilic sulfate film on pyrite.
5) Besides, the effect of pH on the floatability of pyrite with various leaching stages was also discussed.

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In acidic and ammonia alkaline suspensions of sulphur particles each covered with a CuS layer, a disproportionation reaction, i. e., formation of CuS from Cu²⁺ and Cu-NH₃ complex ion, respectively, and concurrent oxidation of S to form SO₄, takes place at appreciable rates. The former is considered to be a cathodic reaction, while the latter an anodic reaction; for example, Cu²⁺+S+2e=CuS (1) and S+4H₂O=SO₄^2-+8H⁺+6e (2), respectively. For eq.(1) data of sulphidising suspension electrolysis show that the rate is very rapid. This is indicative of eq.(2) being therate-determining step. The current density i for the anodic reaction can, therefore, be calculated from the reaction rate and the total surface area of sulphur. The current densities for both acidic and ammonia alkaline suspensions are discussed as a function of the suspension potential E_m (SCE) and pH. It then is found that i is represented by
i=const.[H⁺] ^-mexp [0.87F/RT (E_m-E_o)]
where m is a pH-dependent constant and Eaatentative equilibrium electrode potential.
Sulphur in synthetic CuS is oxidized to form SO₄ at controlled suspension potentials of 0.34-0.36V and to form S at 0.42-0.55V, while that in oxidation residue of Pb concentrate to form SO₄ at 0.25-0.45V. The current densities of these SO₄-forming reactions are the same order. Explanations are given for the effects of the pH and temperature on the S-forming and SO₄-forming reactions for oxidation of metal sulphide. Data for precipitation of CuS with S in acidic solution under SO₂ pressure are compared with the results obtained. It seems that the oxidation rate of SO₂ to SO₄ is about 105 times faster than that of S.

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A mixed CO₂-N₂ gas was injected into aqueous NaOH solution through a glass nozzle of 2.7 to 30.0mm ID and absorption rate of CO₂, gas was measured. The NaOH concentration of the solution was 3 mol·l^-1 and the partial pressure of CO₂ in the gas mixture was kept at 0.1atm. Gas flow rate was varied between 3.0 and 6.0l·min^-1. Frequency of the bubble formation at the nozzle was also measured by a pressure gauge.
Frequency of the bubble formation was 612 to 767 min-1 and mean bubble diameter was calculated as 1.36 to 2.62cm. The overall rate of CO₂ absorption was affected by mass transfer through both gas and liquid boundary layers. Overall mass transfer coefficient of CO₂ absorption was 4.5 to 6.4cm·s^-1 and enhancement factor was estimated as 59 to 84.

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Ternary equilibrium relations were established for zinc or copper sulfate-water-organic solvent system at 298K. Methyl-, isopropyl-, tert. butyl alcohol or acetone was used as an organic solvent.
The results are illustrated on the isothermal diagrams in Figures 2 to 5, and some of the numerical data are listed in Tables 1 and 2. Except of the case of methanol, the existence of miscibility gap was observed in ZnSO₄-H₂O-organic solvent system. The formation of two immiscible layers may be ascribed to the nature of the hydrophobic part of organic solvents. The existence of miscibility gap is not detected in CuSO₄-H₂O-organic solvent system, and the solubilities of copper sulfate decrease remarkably with increasing concentration of organic solvents as shown in Figures 6 and 7.
The difference of salting out effects with transition metal cations can be explained in terms of the standard Gibbs free energy of formation of aquo-metal cation. Dependence of the solubility on the dielectric constant of mixed solvent exhibits delicate variations by the cosolvent and its composition.
The experimental results were discussed and the applicability of data to industrial processes were examined.

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