As a fundamental study on corrosion of refractories by alkali-containing vapor, the present study has been made for the purpose of researching the reactions occurred in the refractory materials such as corundum, mullite and forsterite when they were exposed to vapors from the melt of mixed salt, K₂CO₃-Na₂CO₃, at 1200°C and from the melt of mixed salt, K₂SO₄-Na₂SO₄, at 1300°C.
In the tests with carbonate vapor, the reactions took place through two stages under the condition held in a steady vapor composition and at a constant temperature. At the early stage the mole ratio of K₂O to Na₂O found in the reaction products was almost the same as that in the vapor, whereas at the later stage the products were altered progressively into those richer in Na₂O by replacing K in the products by Na in the vapor. In the respective cases of corundum, mullite and forsterite, the solid solutions of K- and Nacompounds as shown by the following formulas were formed, namely, (K, Na) AlO₂, (K, Na)₃Al₃SiO₈ and (K, Na)_2xMg_xSi_10-xO₂₀ (4≤x≤5). During cooling, however, the solid solutions were separated into two phases of K- and Na-compounds. Consequently, the amount of Na-compounds in the reaction products increased with increasing time of reaction.
In comparison to the tests with carbonate vapor, the reaction velocity observed when tested with sulphate vapor were very sluggish, nevertheless, at the early stage of reaction the mole ratio of K₂O to Na₂O in the product was almost the same as that vapor also in this case.

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Evaporations of chromic oxide and lanthanum oxide component from the sintered body of lanthanum chromite (LaCrO₃) were studied by means of both the target-collection method combined with the Knudsen-cell and the langmuir free evaporation method at temperatures ranging from 1650° to 1900°C in vacuum.
The results obtained were as follows:
(1) The vapor pressure of chromic oxide componet over the lanthanum chromite measured by the target-collection method was about one-fifth of that of pure chromic oxide, and the ratios of vapor pressures of lanthanum oxide component (P_La2O3) to chromic oxide component (P_Cr2O3) were 0.045-0.050.
(2) P_Cr2O3 over LaCrO₃ measured by the Langmuir method was about 1/100 of that measured by the target-collection method mentioned above, and then the evaporation coefficient of Cr₂O₃ was determined as 0.01.
(3) The X-ray diffraction patterns of the surfaces of LaCrO₃ after the evaporations did not show those of mixtures of the usual lanthanum oxide and the chromic oxide and the chromic oxide. It was thus confirmed that the lanthanum oxide contaning 2-3 mol% Cr₂O₃ formed on the surface turned into the C-type rare earth oxide (cubic) at 1900°C in vacuum and that the decomposition reaction proceeding at a boundary between the surface layer of La₂O₃ and the original part of LaCrO₃ was a rate-determining step for the evaporation rate.

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The effect of addition of fluorine on the crystallization of the glass having the composition Li₃Mg_1.75Al₃Si₈O_23.75-x/2F_x, where x=0 to 1.84, was studied. The results obtained are summarized as follows:
1) For a small amount of fluorine content (x=0-1.34), the tendency of the glass to crystallization increased with addition of fluorine. For more amount of fluorine content (x=1.43-1.84), however, the tendency of the glass to bulk crystallization and surface crystallization at relatively low temperatures decreased with addition of fluorine and the crystallization occured throughout the samples at higher temperatures. The cause for this effect of the addition of the fluorine was considered as follows. If it is assumed that fluorine atoms exist in the form of SiFO₃ in the glass, addition of fluorine would weaken the structure of the glass, promoting its crystallization. When the fluorine content is over a certain value (x=1.43), however, the process of the exclusion of fluorine from the formation of the crystalline lattice, and the formation of β-quartz solid solution might be suppressed at relatively low temperatures. It was inferred that the precipitation of tiny MaF₂ crystals in this step might have facilitated the subsequent crystallization of β-quartz solid solution in the bulk of the glass.
2) β-quartz solid solution precipitated in the glass at relatively low temperatures transformed to β-spodumene solid solution at relatively high temperatures. The stability of the former depended on the content of fluorine in the glass. When the glass was heated once at various temperatures, the temperature of transformation decreased with increasing fluorine content. When the glass was heated at a higher temperature after the heat-treatment at lower temperatures, however, β-quartz solid solution was more stable in the glass with richer fluorine content (x=1.84) than in the glass with smaller fluorine content (x=1.34, 1.59). This was attributed to the smaller fluorine content of the residual glass in the sample with x=1.84 than those in the samples with x=1.34 and 1.59.
3) The effects of fluorine content on the bending strength and the thermal expansion coefficient of the crystallized glsses were explained in terms of the state and the thermal expansion coefficient of the precipitated crystals.

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Glass forming region in the system Li₂O-B₂O₃-GeO₂ was determined. Glasses in three series, xLi₂O⋅B₂O₃⋅2GeO₂, xLi₂O⋅B₂O₃⋅GeO₂ and Li₂O⋅xB₂O₃⋅(3-x)GeO₂ were prepared. Measurements of density, refractive index, thermal expansion and Vickers microhardness have been made with these glasses. Infra-red absorption spectra of Li₂O⋅B₂O₃⋅2GeO₂ crystal and glass were also studied.
Rules for the structure of alkali-boro-germanate glass were proposed. The rules are as follows:
(1) BO₄ groups are formed in preference to GeO₆ groups.
(2) Following bonds cannot occur, BO₄-BO₄, GeO₆-GeO₆ and BO₄-GeO₆.
(3) Non bridging oxygen ions cannot belong to BO₄ and GeO₆ groups.
To verify these rules, the relation between properties and structure of lithium-boro-germanate glasses studied was discussed.
It was found that the predictions of these rules were best accord with the observed trend of properties with composition in these series of glasses except for thermal expansion coefficient, which obeyed to Abe's theory.

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Shirasu, which is widely distributed in Southern Kyushu, is mainly composed of the volcanic ash and the pumice. In order to utilize shirasu as the industrial materials, the Production of the Lightweight sand, i. e. perlite, was examined.
Firstly, it was found out in the experiments using an electric furnace that shirasu (the particle size used was under 1.0mm) bloated at about 1000°C by the instantaneous heating, but it didn't bloat by the gradual heating from the room temperature to 1030°C.
The effect of preheating for the bloating was very complex and changed with the particle size of shirasu and the preheating time and temperature.
It was concluded from the following reasons that the main component of the bloating gas in shirasu would be water which was released over 100°C.
1. The weight decrease curves of shirasu by the thermal balance were very analogous with those of the natural volcanic glass rock whose bloating gas was said to be consisted mainly of water.
2. The weight decrease ratio by the thermal balance agreed well with the weight ratio of the water catched in absorbent.
Shirasu enriched with volcanic glass which contained more water bloated better than shirasu enriched with crystals of feldspar, quarz and others.
Nextly, the continuous production of shirasu perlite was performed with an experimental rotary kiln.
Shirasu perlite A and B, which had open pores and closed pores respectively, could be produced arbitrarily by changing the heating speed.
The methods were mainly divided into two of the instantaneous heating method and the heating method with a little preheating.
The bulk densities and the coefficients of water absorption of these shirasu perlites elutriated by air were nearly equal with those of perlites which were sold on the market.
These shirasu perlite-cement mortars showed low thermal conductivity.

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It has well known that the most probale number of sides per polygon in planar random sections of polycrystalline single phase materials lies closer to 5 than to 6.
The present note offers a simple mathematical proof of the fact without any special assumption.
The formula derive here showed that the mean number of sides of polygonal grains in a section asymptotically approached to 5 when the number of glains increased infinitely. 1 fig., 1 table, 3 refs.

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