Definition of "water of hydration" []

• Water chemically combined with a substance in such a way that it can be removed, as by heating, without substantially changing the chemical composition of the substance. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.