Calcium sulfate is a white crystalline powder, odorless, astringent, with a density of 2.960g/cm3, slightly soluble in water and glycerin, and insoluble in ethanol. It is hygroscopic and usually contains two crystal water. One molecule of crystal water is lost at 128 ℃, and all water is lost at 163 ℃. It exists in nature in the form of gypsum ore. The molecular weight is 136.14, which is a colorless monoclinic system. The natural monoclinic system also has a quasi stable monoclinic system due to its slightly cyan color containing impurities, and it turns into a monoclinic system at 1193 ℃.
