Date: circa 1889 water that is chemically combined with a substance to form a hydrate and can be expelled (as by heating) without essentially altering the composition of the substance
WATER OF HYDRATION
Meaning of WATER OF HYDRATION in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012