以上本報では, 通常フォルステライト耐火物製造に用いられる5種類の添加が, マトリックス部分におよぼす影響を荷重下の軟化性状から比較したが, T₁点以後の軟化進行状態を5%圧縮点 (仮にT₅点と名づけたが) までの温度間隔すなわち (T₅-T₁) で比較すると石灰添加の場合が最も良好な結果を示した。又焼締り, 耐火度, 工業的操作の適否等の各観点から綜合的に判断して, 石灰添加が最も望ましいことを示した。

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On the glass sealing of vacuum tubes, the intermediate glass of law melting point can be used effectively.
The results of the work are as foffows.
1) The fact is confirmed theoretically that the sealed tubes are safe from crack and leakage, when the relativities of expansion coefficient between the bulb glass, stem glass and intermediate glass ars suitably selected.
2) A few sealing methodes are tried practically.

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The authors, in continuing the previous studies (This Journal, 59, 61 and 202, 1951) on the relation between chemical compositions and waser solubilities of special glasses containing zirconia in soda-lime-silica glass type (Na₂O-CaO-ZrO₂-SiO₂), reported in the present paper the results of further studies on the water solubility or water resisting degree of various special glass samples containing boric oxide B₂O₃ in the above mentioned soda-lime-zirconia-silica glass (Na₂O-CaO-ZrO₂-SiO₂-B₂O₃), in amounts of 2, 4, 6, 8, 10 and 12% by replacing silica, lime or soda.
The tests were carried out by the powder method with various heating conditions in water, as following: (1) under the atmospheric pressure on water bath, and (2) under the hydrothermal pressure of superheated steam in the closed autoclave by the following four cases. (a) 8 atm. and about at 172°C, (b) 17 atm. and about at 205°C, (c) 25 atm. and about at 225°C, and (d) 40 atm. and about at 251°C. The results of these experiments, (1) cc of titrated N/50-H₂SO₄ solution, (2) the percentage of dissolved alkali (AS) by the calculation, (3) the percentage of dissolved alkali and silica as weight decrease (WD), and (4) the percentage of the dissolved alkali to the weight decrease as (AS)/(WD), were odtained and fully discussed. The results were compared with those reported in the previous reports (IX and X) (loc. cit.), and it was determined to be able to obtain the special glass of good water resisting property, which is the special glass type of soda-lime-zirconia borosilicate glass, containing SiO₂: 66-68%, ZrO₂: 6-8%, B₂O₃: 10-12%, Na₂O: 2-4% and CaO: 3-5%.

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