nonahydrate

Nonahydrate refers to a hydrated chemical compound that contains nine molecules of water of crystallization per molecule of the anhydrous compound. This water is incorporated into the crystal structure of the substance and can be released upon heating. The presence of this water can significantly alter the physical properties of the compound, such as its melting point, solubility, and appearance. Many common inorganic salts, for example, can exist in hydrated forms, and nonahydrate is one such specific hydration state.

The chemical formula of a nonahydrate is typically written by indicating the anhydrous compound followed by a dot and the number of water molecules. For instance, a hypothetical nonahydrate of a salt "X" would be represented as X·9H₂O. The water molecules are not simply adsorbed onto the surface but are chemically bound within the crystal lattice, often coordinated to the metal ions or forming hydrogen bonds with the anion.

The determination of the hydration state is important in chemical analysis and industrial processes. Heating a nonahydrate will drive off the water molecules, leading to the anhydrous form. The temperature at which this dehydration occurs is dependent on the specific compound. Some nonahydrates are stable under ambient conditions, while others may be more sensitive to humidity or temperature changes. Examples of compounds that can form nonahydrates include certain sulfates and phosphates, though specific examples are less common than lower hydration states like monohydrates or dihydrates.