著者

村上 恵一 田中 弘文 成田 光昭 三塚 雄一

出版者

無機マテリアル学会

雑誌

石膏と石灰

巻号頁・発行日

vol.1966, no.84, pp.163-169, 1966

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The calcium sulfate hemihydrate obtained by the decomposition of the Kola Phosphate Rock with H<SUB>2</SUB>SO<SUB>4</SUB> fairly differs from a common calcium sulfate hemihydrate in physical and chemical properties.<BR>The time of hydration of this hemihydrate is extremely long in 30% P<SUB>2</SUB>O<SUB>5</SUB> solution or water.<BR>This is caused by the peculiarity of the crystalline formation of the hemihydrate, and the results of the study are summarised as follows.<BR>(1) Though the common hemihydrate from the Florida rock contain about 0.07% Sr, this hemihydrate is characterized by containing high content of it about 1. 5% Sr.<BR>(2) By the precise measurement of X-ray diffraction patterns, it is made clear that the crystal lattice of the hemihydrate slightly expends as compared with the hemihydrate from Florida rock.<BR>This phenomenon will be explained because ionic radius of Sr is longer than that of Ca and the solid solution of strontium sulfate in calcium hemihydrate will be formed.<BR>(3) As this hemihydrate is much easier to lose the crystal water than that from Florida rock, the crystal water decreased to about 3% after five days in desicator, but that from Florida rock does not lose crystal water in desicator.