In order to apply a seeding method using silica gel to silica removal from geothermal brines, the effects of the seed particle diameter, initial specific surface area and initial pore diameter on silica removal are experimentally examined using a model geothermal brine. The silica in the brine is precipitated on the internal surface area of pore in the silica gel seeds. The specific surface area of the seed decreases with increasing quantity of precipitated silica. The effects of the particle diameter on the quantity of the final precipitated silica and on the final specific surface area are hardly seen. The quantity of precipitated silica per unit surface area increases with increasing initial pore diameter, and the silica precipitation rate coefficient increases with decreasing particle diameter and with increasing initial pore diameter. When the quanttty of precipitated silica is small, the silica precipitation rate coefficient is proportional to the -0.72 power of the particle diameter.

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The present paper describes the statistical simulation results for the deviation of the sample size destribution function, which stems from the multiple counting of particles in the measurement of particle sizes by using a microscopy method. The multiple counting factor expected for a sufficient number of measurements depends strongly on the apparent measuring fraction, irrespective of the sample size projected in the unit measurement area. Although the multiple counting factor increases with an increase in the apparent measuring fraction, the deviation in the sample size distribution function decreases gradually because there is a suffcient number of observed particles. It is concluded that, for practical usage, sampling conditions of the apparent measuring fraction of>0.2 reasonably insure a deviation of<3% for the sample size distribution function.

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The effect of the water contet and crystallinity of heptakis-(2, 6-di-O-methyl)-β-cyclodextrin (DM β CD) on the physicochemical properties of a sealed heated compound with naphthalene was investigated using powder X-ray diffractometry, thermal analysis and solid state fluorescence spectroscopy. The water content in amorphous DM β CD affected the inclusion formation of stable and metastable inclusion compounds, even if it had little influence on the inclusion molar ratio. A suitable amount of water (1%-4%) caused metastable inclusion formation between DM β CD and naphthalene. After the sealed heating of crystalline DM β CD and naphthalene, only stable inclusion compound was obtained. It was found that amorphous DM β CD containing a small amount of water could form a 1:2 inclusion compound with naphthalene.

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This study was undertaken to clarify the effect of the mixing condition of SnO₂ and glass partieles on the densification behavior, the microstructure and the electrical properties of the glass composites containing semiconductive SnO₂ particles prepared by a mechano-chemical process. The relationship between the electrical properties of the glass composites and the dispersion state of the SnO₂ particles in a glass matrix was discussed based on the results of the quantitative analysis of SnO₂ particle dispersion by the computer-assisted image analysis of SEM photographs.
The results are summarized as follows:
(1) The homogeneity of the mixing state of SnO₂ and glass particles mainly depends on the degree of pulverization of the glass particles because the SnO₂ aggregates formed during the mechano-chemical synthesis of the SnO₂-Sb₂O₃ powder mixture are easily disintegrated during ball or attrition-milling. Therefore, when the mixing condition in which glass particles are effectively pulverized, such as in attrition milling, is applied, homogeneous mixing is easily achieved, and densely sintered glass composites with homogeneously dispersed SnO₂ particles are obtained at low firing temperatures.
(2) The electrical conductivity and the temperature coefficient of resistivity (TCR) of the glass composites fired at low temperatures largely depend on the degree of densification. The glass composites well densified at low firing temperatures, such as an attrition-milled sample, show a high electrical conductivity and a small negative TCR at low firing temperatures.
On the other hand, the electrical conductivity and TCR of the glass composites fired at high temperatures are significantly influenced by the SnO₂ particle dispersion in a glass matrix. When comparing the densely sintered glass composites, the electrical conductivity becomes higher, and TCR approaches zero when the highly aggregated SnO₂ particles form networks in the glass matrix.

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