著者

安達 正雄 谷本 明

出版者

無機マテリアル学会

雑誌

石膏と石灰 (ISSN:21854351)

巻号頁・発行日

vol.1975, no.135, pp.63-72, 1975-03-01 (Released:2011-03-07)

参考文献数

75

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To analize mechanism of calcium scale deposit on heated wall in evaporator, accurate solubility data of calcium sulfate in pure water are required, but satisfactory data are not available from databooks. Therefore, an attempt to determine the equations which represent accurately the solubility of calcium sulfate is performed.All the solubility data which are taken from available original literatures are classified in five groups corresponding to modifications of calcium sulfate, i. e. dihydrate, α-and β-hemihydrate, soluble anhydrite and insoluble anhydrite. The equations for each group are determined by so-called double-minimum-square method using digital computor FACOM 230-35 of Kanazawa University.It is found that all the data for soluble anhydrite are obviously classified in two groups. Because of this fact and the other verification, two types of α and β exist in soluble anhydrite. At last, the equations of solubility for six modifications of calcium sulfate are presented. Deviation of the data from the equations are less than ±10% for temperature ranges from 0 to 170 or 200°C, but for dihydrate ±-1%, 0 to 110°C.It seems that the given each equation of solubility for modifications of calcium sulfate is the most accu-rate, comparing with the other's solubility equations.