Pronunciation: (hī'drāt), [key]
—n., v., -drat•ed, -drat•ing.
any of a class of compounds containing chemically combined water. In the case of some hydrates, as washing soda, Na2CO3·10H2O, the water is loosely held and is easily lost on heating; in others, as sulfuric acid, SO3·H2O, or H2SO4, it is strongly held as water of constitution.
to combine chemically with water.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.