Phase relations in the CaO-Fe₂O₃-(FeO)-H₂O system are investigated between 200°C and 700°C, and under water pressures of 100atrn, 300atm and 1, 000atm. The assemblage of Ca (OH) ₂ and iron oxide (s) is stable under the water pressure of 1, 000atm and/or between200ºC and 500°C. CaO·Fe₂O₃ is stable above 600°C and below 300atm Only under 100atm, 2CaO·Fe₂O₃ and 4 CaO·FeO·4Fe₂O₃ are stable at 700°C and above 600°C, respectively. These results suggestthat calcium ferrites, which are important in the self-fluxed sinter, can be formed at lower temperatures under the hydrothermalcondition than in air.

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Theory and the laboratory test results on the low cost stress meter which has a structure that the strain rosettes are pre-cast into the cylindrical shaped moulding material, therefor, which is called a moulded gage, are described. Two types of the moulding materials, named type 1 and type 2, of which rigidities are small in comparison to those of the high modulus meters, have been developed for this purpose. The former is suitable to measure the absolute stress. On the other hand, the latter is suitableto monitor the stress change for long term measurement.
The meter has the following merits; First, the complete state of stress can be determined in a single measurement (Eq. 2 is the observation equation for this gage). Second, the gage sensitivity issufficiently high. Third, the results of the measurements are less dependent on the elastic constants of the rock in comparison to those obtained by the soft meter like the borehole deformation gage.
Satisfactory agreement between the actual and measured stresses was obtained by the laboratory test to simulate the measurement of the absolute stress.

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Sometimes, in mines, it is indispensable to calculate explosibility of mine gases during such events as underground fires, spontaneous combustions of coal and so forth. Therefore, up to the present, many explosibility estimation methods have been proposed.
An explosibility estimation method should provide two important features, ie., rapidness and precise informations about status of explosibility of a gas mixture. Most of conventional methods adopt simplification in calculation procedure in various ways to approach to rapidness. Some of them lack in preciseness and informations of estimation results.
In this paper, the authors present a new estimation method which provides almost all factors to be needed for explosibility judgement, explaining bliefly about the programming flow-sheet, and finally showing, some typical estimation examples which have been calculated with the computer, TOSBAC 3400 of our Institute.

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The volumetric concentration of solid particles in pipeline was measured by a concentration meter of horizontal U-pipe type installed on the way of 2-inch pipeline of testing apparatus.
Flow of solid-water mixture in a bend composing the horizontal U-pipe was considered. As a result it may be thought of that information obtained from the concetration meter of this type having four bends equals to approximately that obtained from. the meter of horizontal straight pipe type.
Samples of the solid particles were fine gravel, coarse sand, fine sand and coal of mean size 10.5mm.
The ratio of the volumetric concentration in the pipeline to the deri vered volumetric concentration Cv_i/Cv_owas studied in relation to Froude pumber vw²/{gD (s-1)}.
In a given sample, the ratio Cv_i/Cv_owas a constant independently to Cv_oin the range from 6 to1 5 of the Froude number, therefore the authers' experiment gives support to a result of R.C.Worster and D.F.Denny.
Although Worster and Denny gave Cv_i/Cv_o=1.13, it seemsto be particular value. Our experiment indicated that the ratio Cv_i/Cv_o was proportional to nondimensional group (v_f√gD) In (D/d_s) in the range of the Froude number, where vf is the mean free settling velocity of the solid particles, D is the pipe diameter, ds is the mean diameter of the solides particles and g is the acceleration of gravity.
The nondimensional group (v_f√gD) In (D/d_s) may be regarded as a criterion of easiness of horizomtal hvdraulic transportation of the solid particles in the heterogeneous flow without deposision. The solid sample which thenomdimensional group gives a small value will be transported more easilythan in case of a large value.
Furthermore, the ratio of difference between the mean velocity of water and the mean velocity of the solid particles to the mean velocity of water (vw-vs)/vw was compared with another nondirhensional group (v_w-v_s) 2/{gD (s-1)}.As a result, it was shown that the ratio (v_w-v_s)/vw has a minimum value in horizontal transportation in a pipe.

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The application of an experimental X-ray fluorescence analysis characterized by rapid, elemental or surface analysis to the study of adsorption measurement in flotation process is described. The amount of adsorbed chromium was measured by counting the X-ray intensity of Cr-Kα on galena sample surface adsorbed in aqueous solution of potassium dichromate at 25ºC, as a function of adsorption time and concentration of the solutions varied from 0.1to 1, 000mg Cr/l together with pH of the solution. The results obtained by the X-ray fluorescence analysis gave faster and moreprecise determination of adsorbed chromium comparing with those by the conventional spectrophotometric analysis of the solution concentration. It is emphasized that the direct determination of the adsorbate by the X-ray fluorescence analysis may be successfully utilized for the adsorption study of depressor, regardless of any side reaction such as precipitation in the flotation pulp.

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In the previous paper the co-precipitation process with ferric hydroxide was investigated to remove As contained in waste water.Since fine MnO₂powder obtained by electrolysis at lowtemperature was fou nd effective to remove the As ions, the optimum conditions were studied in this paper for both arsenous and arseni c solutions.
When the solution containing 10ppm As wastreated with MnO₂2g/l, the minimum content of As in the solution such as 0.15ppm was reached at pH 2 regardless of As³⁺or As⁵⁺. The As absorbed on MnO₂may be leached out by 2N-NaOH solution with a yield of high As content solution and the active MnO 2 applicable tof urther treatment. In the same way the iron precipitate in low As contentand high As solution were obtained by treating the precipitate of ferric hydroxide containing As with 0.5N-N_aOH solution.
As the co-precipitation process with ferric hydroxide suggested that the better result was expected when As in the solution was oxidized to As⁵⁺ion, the oxidizing effect for As³⁺was studied by using N_aOCI and C_a (OCl) ₂.

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Hydrolysis reaction in Co (II)-H₂O system have been investigated thermodynamically and experimentally, at temperaturesbetween 25°and 200°C. The results are summerized as follows:
(1) The chemical potentials of relating substances at 25°to 250°C were derived by several thermodynamic ways.(2) The hydrolysis equilibrium was discussed thermodynamically, and it was predicted that CoOH⁺would not be predominantunder the conditions considered.(3) The pH dependences of solubility of Co (OH) ₂were measured at temperatures between 25°and 200°C. pH values were measured directly at equilibrating temperatures below 100°C, but were measuredat 25°C for quenched solutions in the experiments above 100°C.(4) Correspondence of pH values between 25°and t°C based on eq.(23) in this paper was confirmed by experiment.(5) Red Co (OH) ₂were precipitated in the experiments at above 90°C and thermodynamic behavior agreed well with the theoretical predicitions (Fig. 10).(6) A bluish active Co (OH) ₂was precipitated at 25°C as a metaslable form, and for this active hydroxide K_sp=7.8·10^-15, μ°₂₉₈=-107.7 kcal/mol were derived

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