Tetrahydrate
Encyclopedia
A tetrahydrate is a molecule surrounded by four (4) molecules of water, forming a hydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....

. The notation for a tetrahydrate is anhydrous
Anhydrous
As a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another...

molecule's formula
·4H2O, where the 4 represents tetrahydrate, and the H2O represents the tetrahydrate. And the molecule's name changes to anhydrous molecule's name tetrahydrate.
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