無水石膏より結晶石膏への轉化に關する研究 (第1報) 常温浸漬試驗について

概要

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To obtain well-crystallized gypsum crystal (CaSO4.2H2O) for making gypsum plaster (CaSO4.1/2H2O) of high quality, the studies on conversion of anhydrous gypsum (CaSO4.2H2O) were systematically carried out. In the present report, the results of experiments were summarized and reported, as following: (1) Anhydrous gypsum was obtained as byproduct from making hydrogen fluoride by the double decomposition CaF2+H2SO4=HF+CaSO4, (2) Another anhydrous gypsum was obtained by calcining powder of natural crystal gypsum to 400, 700 or 1200°C for 30 minutes CaSO4.2H2O=2H2OCaSO4, (3) These samples of anhy-drous gypsum powder were dipped in 5% solution of various salts of Al-, Fe-, Mn-, K- or Na- and sulphate or nitrate at room temperature for 3, 7, 14, 21 or 28 days, (4) Tbedegree of conversin of the anhydrous CaSO4 to crystal CaSO4. 2H2O was compared by determining the amount of crystal water, (5) The crystal form and size of thus obtained gypsum crystal were strictly compared, (6) Solution of aluminium or iron sulphate [Al2(SO4)3 or Fe2 (SO4)3 gave best results of anhydrous gypsum to large tablet form of gypsum crystal, which can be made by calcining to gypsum plaster of highest quality, and (7) These experiments are now being further continued, which results will be hereafter reported in the next report
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