One of the important properties of the checker bricks is the resistance to attack of the variours vapour of batch materials and the melting glass at high temprature in the tank.
In this paper, the corrosion process of magnesia brick under influence of the vapour of boric oxide is studied by changing the temperature and the time of corrosion by its vapour.
At the temperature of 1300°C, magnesium-orthoborate (3MgO⋅B₂O₃) was formed in all portion of the brick, but after about 20 hours in this reaction process, liquid phase of composition of magnesium-metaborate (MgO⋅B₂O₃) was formed at the surface of the brick.
But, at the temperature of 1400°C, only magnesium-orthoborate (3MgO⋅B₂O₃) was formed through all reaction process. It is supposed that as the reaction product (3MgO⋅B₂O₃) in the first rcaction process was formed in liquid phase directly this product had no chance to change into the next reaction product (MgO⋅B₂O₃).

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Notwithstanding water content of phosphate glass is, in general, exceedingly greater than that of silicate or borate glass, it is rather difficult to gather informations about influences of water on structure and properties of glass.
First, in purpose to study on this problem more thoroughly, the writers prepared a vast number of glass samples having the different values of MO/P₂O₅ ratio, R_M, or (MO+H₂O)/P₂O₅ ratio, R_MH. Water content of glass was regulated by means of repeated remelting. Various series of samples suitable to understand the influences of water content on structure and properties of glass were taken up from those many samples prepared. And then, it was attempted to clarify behavior of water in glass structure.
From the results of infra-red spectrophotometry and measurements of characteristic properties of glass, it was proved that, in whichever system, R_MH had much more important significance as a composition parameter rather than R_M.
In reference to R_MH and R_M values, considering behaviors of the end and the middle OH-groups in glass structure and the effects of electron donating power of element M and field strength or polarizability of M²⁺ ion on hydrogen bond (OH…O) in glass, one can explain, from a structural viewpoint, the influences of residual water on the characteristic properties of glass, especially, density and refractivity. Thus, the following interesting findings were obtained.
(1) Density of glass decreased with decreasing water content. This reveals that, in general, dehydration makes to expand the glass structure. However, in case that the middle OH-groups in glass of anomalous type, e.g., those in the system MgO-or ZnO-P₂O₅, were obliged to be removed from the structure, the glass resulted in structural contraction rather than expansion.
(2) In respect to the series of samples almost constant in H₂O/P₂O₅ ratio, it could be found that an anomalous change of density and refractivity occurred when R_MH=1. Therefore, R_MH-value should be dealt with as a conclusive composition parameter for marking the structure exchange of water containing phosphate glass. Especially, the physical properties of magnesium phosphate glass showed a drastic change at the critical composition, presumably, on account of a particularity of the glasses of anomalous type.

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市販ポルトランド中にどのような種類の含水化合物が存在するかを, 示差熱分析およびカールフィッシャー試薬を用いる水分測定法により検討したところ, 試料セメントによっては, 石膏, 水酸化カルシウムのほかにSyngenite (K₂SO₄・CaSO₄・H₂O) が生成していることを認めた. Syngeniteは, DTA曲線において270℃に顕著な吸熱ピークを示し, そのピーク面積からの定量によると12個の試料のうち最大1.2%, 平均0.59%の含有量を示した. 2水塩としての石膏の含有量は, 平均0.5%にとどまり, おそらくボールミル粉砕中に大部分脱水していること, および全遊離石灰中, 平均75%の酸化カルシウムはCa(OH)₂の形で存在することを知った.

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