Ordered Water: Just how much water is there in calcined gypsum?

(PhysOrg.com) -- Gypsum was used as a building material in antiquity and is still widely used as a binder in plaster, drywall, and spackling paste. Known as dihydrate in construction chemistry, gypsum is a water-containing calcium sulfate (CaSO₄• 2 H₂O). In various calcination processes, some of the water of crystallization is removed, resulting in calcined gypsum, or hemihydrate (CaSO₄• 0.5 H₂O). When this material comes into contact with water, it reabsorbs it and sets up. The structure and exact water content of hemihydrate have remained a matter of speculation.

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<p><a href="http://www.physorg.com/news159012528.html">Ordered Water: Just how much water is there in calcined gypsum?</a></p> <p>(PhysOrg.com) -- Gypsum was used as a building material in antiquity and is still widely used as a binder in plaster, drywall, and spackling paste. Known as dihydrate in construction chemistry, gypsum is a water-containing calcium sulfate (CaSO₄• 2 H₂O). In various calcination processes, some of the water of crystallization is removed, resulting in calcined gypsum, or hemihydrate (CaSO₄• 0.5 H₂O). When this material comes into contact with water, it reabsorbs it and sets up. The structure and exact water content of hemihydrate have remained a matter of speculation.</p>