Hydrates of Gypsum
Date: December 10, 2002
What is the difference between half-hydrate and
hemihydrate of gypsum?
They are the same. Either way you call it, half hydrate or
hemihydrate, the substance is Plaster of Paris. Natural
gypsum is the dihydrate form of calcium sulfate.
There is an entry in the Newton database that describes the
water-proportional chemistry of the two forms.
David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory
As far as I know, they are the same thing, otherwise known as plaster of
Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois
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Update: June 2012