Mystery calcium sulfate
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Here is an example label from a gypsum replacement product of ambiguous composition. It claims to be gypsum and derived from CaSO4*2H2O, but the chemical abstract citation for 41798-04-0 indicates that the product is actually calcium sulfate anhydrite, CaSO4. Only the gypsum quick test will help you figure this one out. Gypsum quick test. If you are interested in the CAS number for gypsum it is 13397-24-5.
