Monohydrat

Monohydrat, also known as monohydrate, is a chemical substance that contains exactly one molecule of water for each formula unit in its crystal lattice. It is a type of hydrate formed when a compound crystallizes from an aqueous solution or when water becomes bound to the solid. The water molecules are called waters of crystallization. In chemical formulas, monohydrates are indicated by a dot followed by H2O, for example CaC2O4·H2O (calcium oxalate monohydrate).

Hydrates can lose or gain water. Upon heating, a monohydrate may dehydrate to form the anhydrous compound, and rehydration can occur when the solid is exposed to moisture in the air. The presence of one water molecule per formula unit can affect properties such as solubility, stability, and crystal structure, making monohydrates distinct from other hydrates with more or fewer water molecules.

Common examples include calcium oxalate monohydrate (whewellite), which occurs as a mineral and can be found in kidney stones; glucose monohydrate, a crystalline form used in some pharmaceutical and food contexts; and copper(II) sulfate monohydrate (CuSO4·H2O), a dehydration product of the pentahydrate in certain conditions. The study of monohydrates is important in crystallography, mineralogy, and chemistry because water content can influence processing, storage, and reactivity of materials.