Well crystallized sepiolite was treated by AlCl₃ solution under hydrothermal conditions and at room temperature as well. The products were examined by X-ray, thermal, infrared absorption and electron microscopy methods. In addition, Si, Mg and Al in the solution were determined by atomic absorption analysis.
In this experiment, kaolinite was formed by the treatment with 3.0N, 0.1N and 0.8N AlCl₃ solution above 200°C, and dioctahedral smectite was obtained with 0.5 N and 0.2N solution above 200°C. Therefore, it has been made clear that in this experiment the Al concentration in the solution and the temperature play the most important role.
The reaction may be considered to proceed in the following sequence:
sepiolite→amorphous material→kaolinite→dioctahedral smectite

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It is seen from an observation of steam and hot water flow rates for a long period of 7 to 10 years that there are three kinds of decline, namely (1) steam flow rate shows a decline of 3 stages for 0-7 production well, a fixed rate for 0-8 and 0-9, and a periodical decrease for 0-10 and the total of 4 production wells at Otake, and (2) hot water rate gives a linear decrease of two stages, a periodical increase for 0-9 and 0-10, and a periodical change for 0-8 and the total of 4 production wells. Of course, the mutual interference exists between 0-8 and 0-10.
After the reinjection, (1') steam flow rate shows an unchange for 0-8, a little increase for 0-7 and 0-9, and an increase for 0-10 and the total, and (2') hot water flow rate gives such various declines as a fixed state for 0-8, an increase for 0-7 and 0-9, a periodical decrease for 0-10, and a periodical increase for the total.
Dryness fluctuations and the inclination of the enthalpy of a steam-water mixture before reinjection show a gradual increase for 0-7, a decrease in step for 0-8, a slight increase for 0-9, an irregular decrease for 0-10, and a periodical decrease for the total. After the reinjection, they show a decrease for 0-7, a definite increase for 0-8, a little increase for 0-9, an increase and decrease for 0-10, and a periodical change for the total.
Heat discharge from wells indicates two kinds of tendency, that is, one is in unchanged state by the reinjection, which applies to 0-8 and 0-10, and the other is in increased state for 0-7, 0-9 and the total.
The effect of reinjection to the production wells is that the steam rate from 0-7 is affected by R2, and hot water flow rate, dryness, enthalpy and heat discharge from the same well are subiect to the influence of the reiniections, Rl and R2. In 0-9, steam flow rate and heat discharge show an increased state under the influence of reinjections, R1 and R2, which produce an effect upon hot water flow rate graph. In 0-10, steam and hot water rates, dryness and enthalpy are influenced by the reinjection, R2. The influence of reinjection, R1 and R2 occurs on the curves of steam and hot water flow rates, dryness, enthalpy and heat discharge for the total of 4 production wells. Particularly, no influence of reinjection is obtained for 0-8 production well.
Finally, the production capacity of geothermal energy for 4 wells is written as 0-9, 0-10, 0-8, and 0-7 in descending order.

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The fracture crack initiation around a small circular hole in the rectangular plate of rock specimen is observed as a model of borehole and circular cross-sectional roadway under the uniaxial compression.
In this experiment, the following unexpected phenomena are observed:
(1) the first fracture crack around the borehole is observed frequently in the region of compressive stress concentration;
(2) the tensile fracture crack initiated at the top and bottom wall of borehole propagates up to some limited length, to be arrested;
(3) the external stress (load) for the fracture crack initiation is dependent on the diameter of borehole;
(4) the external stress for the fracture crack initiation is much greater than that expected from the elasticity of isotropic homegeneous body.
All of these phenomena are not explained by conventional theories. However, applying the theory and concept of the linear fracture mechanics, all of these phenomena are explained as results of the interaction between the circular hole and pre-existing Griffith crack.

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The behaviors of Fe, S, O and SiO₂ in the heterogeneous equilibrium system between liquid copper, white metal, silica-saturated iron silicate slag and SO₂ gas, were investigated at 1300°C as a function of partial pressure of SO₂ (pso₂) varying from 0.007 to 0.2 atm. The quenched samples were analysed chemically, and the thermodynamic explanations were given to the results. The obtained results are summarized as follows:
(1) In the slag, with increase in pSO₂ (which is proportional to pO₂), the solubility of SiO2 decreases, while the (Fe^III/Fe^II) ratio increases. Because of thedissolution of copper oxide, the solubility of silica in slag is higher than that in the plain FeO-Fe₂O₃-SiO₂ system. These results are similar to those of previous studies for Cu-slag-O₂ system.
(2) In the white metal, with increase in pso₂, the content of iron decreases, while of oxygen increases. It is reasonably assumed that iron and oxygen behave as Fes and Cu2O respectively. At infinite dilution in the each binary of Cu₂ S-FeS and Cu₂S-Cu₂O, the activity coefficients of FeS and Cu₂O are γ°_Fes≈0.4 and γ°Cu₂O≈1 respectively.Interaction parameter in the ternary Cu₂S-FeS-Cu₂O system is εCu₂OFes≈ε FeS Cu₂O≈-27.
(3) In the metal, with increase in pso₂, the content of S shows rather constant value (-1%) while the contents of iron and oxygen show similar tend encies with those in the white metal but the values are less than one tenth. The reliable data could not be obtained for oxygen probably due to the evolution of SO₂ during solidification.

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