The gamma-ray dose rate distribution in a small closed space, 80mm in dia., 110mm in high, was determined by the use of small pieces of ordinary plate glass, 15×6×1.72mm, as a dosimeter. The technique of the measurement was described. The advantageous features of the glass dosimeter, i.e., its small size, convenient usage, and preciseness in the measurement, were discussed. A brief description of the construction of a small Co-60 irradiator, in which the measurement was made, was appended.

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陶磁器や耐火物を製造するばあいに最も重要な工程は壊土の調整にあり, この問題を解決するためには使用する原料の特性, 粒度分布, 混合, 成形方法, 乾燥と焼成の条件などについて注意することは当然であるが, 実験で明らかにされたように, “ねりかた” によって, 得られる素地と製品の性質が左右され, しかも同じ機械を用いても素地の組成や性質によって著しく異なってくることが明らかにされた. 従って調整ということは目的の製品に要求される性能を考慮して初めて考えられることで, この事実を掌握しておかなければ,その組成で最高の製品を得ることは不可能であるわけである. 特にねり土のつくりかた, あるいは成形時の圧力のかかりかたによる粒子の配向性のために収縮の方向性, 加熱による膨脹収縮の方向性, 乾燥速度の差異などが必然的に発生し, 結果的には製品の収率に著しく差を生ずるので, 調整に当っては使用する操作様式の詳細を明確に知っておかなければならないことになる.

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This is the first paper in a series of articles concerning the thermodynamic considerations of the possibility and its related problems that silicate glasses would have the “microheterogeneous structure” containing different types of SiO₄ groups. Methods of thermodynamic applications available for the considerations mentioned above are presented, together with examples of the calculations.
A semi-empirical method is described to estimate the entropies per mole of SiO₄ group for the fundamental building units of crystalline and/or vitreous silicates. These entropies may be estimated by means of dividing the “molal” entropy of each building unit, which is expressed in the form of rational formula, by the number of SiO₄ groups contained in the unit. The entropies of the building units are determined from the entropies of silicate compounds. As for the standard entropies of silicate compounds which have not been experimentally determined, these can be approximately computed by the use of K.K. Kelley's rule (1943) which was summarized in the form of a rule by W. J. Knapp and W. D. Van Vorst (1951).
The method for calculations is presented to obtain free-energy changes for such reactions concerned in the formation of silicate glasses that a silicate is resulted from the combination of other silicates and/or the combination of another silicate with silica. The standard changes of enthalpy per mole of each reacting SiO₄ group for the abovementioned reactions at room temperature are calculated by the use of additive relationships shown by M. L. Huggins and K. -H. Sun (1946) for the energy of formation of oxygen-containing inorganic crystals and glasses from their component ions in the gaseous state. The standard changes of entropy per mole of each reacting SiO₄ group for the foregoing reactions are obtained by making use of the above-mentioned semi-empirical method concerning the estimation of entropies for fundamental building units of silicates. The standard changes in Gibbs free-energy for those reactions are easily determined from the foregoing two kinds of thermodynamic functions. This method may be available for the estimation of the effect of the error contained in entropies computed by the additive law on the value of free-energy change when accurately determined entropy data are lacking, provided that the appropriate values of the error are added in the calculation. The values of standard change in free energy at elevated temperatures are calculated by the methods well established in thermochemistry in the case that heat-capacity data at those temperatures are available, and are also estimated by means of the approximation emphasized by F. D. Richardson, J. H. E. Jeffes, and G. Withers (1950) in such cases that the heat-capacity data are not available.
These free-energy calculations will allow for the prediction of equilibria for the above-mentioned reactions concerned in the formation of silicate glasses. Two examples for the calculations are given. One of them is for the reaction in the standard state at room temperature between the building units of sodium orthosilicate and of silica to form the building unit of sodium metasilicate. Another is for the reaction at elevated temperatures resulting in the building unit of sodium disilicate from the combination of the building unit of sodium metasilicate with that of silica.

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This paper presents the results of the investigations on the effect of vanadium oxide on the oxidation of pure silicon oxide powder, since the former has proved to be most influential material for such action (J. Ceram. Assoc., Japan, 67 [6] 189 (1959)).
V₂O₅ melts at 660°C and in order to investigate the wettability of the molten oxide against silicon carbide the change of contact angle by temperature as well as the penetrability of the molten liquid into the powder were measured.
Through the measurement of the change of weight and by X-ray analysis of mixed powder heated in argon atmosphere the temperature dependency of the chemical reaction and its details were studied. From the results obtained the rate of reaction at 950° and 1150°C in oxygen stream was measured. Furthmore, through the measurement of the penetrability V₂O₅ into thedry-pressed silica powder, and of the pyrometric cone equivalent temperature of the mixture the author has tried to approach to the mechanism of chemical reaction.
The results are summarised as follows:
1) Large wettability of SiC with the melt from V₂O₅ in air as well as in argon atmosphere was confirmed. At the temperatures higher than the melting point the contact angle decreased rapidly approaching soon to practical zero value. No bubble at the interface was observed. Also, the melt denetrated rapidly into the pressed mass of the fine powder of SiC. Especially, the rate of penetration of the melt into the pressed silica powder was to be very high between the temperatures of 950° and 1150°C.
2) V₂O₅ reacts with SiC in three steps in the atmosphere of argon, namely at 640°-670°C, 750-920°C and 1020°-1180°C-. It was confirmed that V₂O₅ was reduced to V₂O⁴ in the second step, and to V₂O₃ in the third step. The temperature of the completion of the third step changed by the nature of V₂O₅, but not by the kind of SiC used. On the other hand, as V₂O₃ was oxidized to V₂O₅ through V₂O₄ at the temperatures as low as 500°C, and it may be concluded that the coexistence of O₂ is to accelerate the rate of oxidation of SiC by V₂O₅ which naturaly will be influenced strongly by temperature.
3) When V₂O₅+SiC mixture was heated to 900°C in argon and then O₂ was introduced oxidation proceed very slowly at the begining, fast gradually, and again slowed down with time. This may be interpreted by assuming the fact that when SiO₂, the reaction product of the oxidation of SiC, accumulate over ten per cent the migration of V⁺⁵ became difficult owing to the solidification of the melt. In this stage V₂O₄ is formed at the interface.
4) When the same experiment was carried out at a higher temperature, 1150°C, two types of the reaction were observed, namely
a) When all V₂O₅ was reduced to V₂O₃ the reaction rate was possible to be expressed by a second order equation, i.e. very high at the initial stage falling gradually with time.
b) When most part was reduced to V₂O₄ the reaction represented by the equation.
logΔr=kt+c,
where Δr is the amount of the oxidized SiC measured by the thickness from the surface, t is the time, and k, c are constants.
Taking a serious view of the roll played by SiO₂ at the interface between the oxide film and the surface of SiC crystal the author discussed the mechanism of the oxidation of SiC with the mobility of V⁺⁵ in the system SiO₂-V₂O₅ and the cone equivalent temperature.

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