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Name: Naveed
Status: Educator
Age: 30s
Location: N/A
Country: N/A
Date: December 10, 2002
Question:
What is the difference between half-hydrate and hemihydrate of gypsum?


Replies:
Naveed,

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 Paris.

Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois


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