oktahidrál

Oktahidrál is a fictional chemical term used in educational contexts to describe a metal salt that forms eight water molecules of crystallization, i.e., an octahydrate. The term derives from octa- meaning eight and hidrál, a cognate related to hydration in some languages; in English the standard term would be octahydrate.

Concept and scope: In theoretical discussions, oktahidrál serves as a placeholder to illustrate how hydration affects properties such as solubility, melting point, and lattice energy. The exact metal and anion are not specified; any chosen MX salt could be described in its octahydrate form as MX·8H2O.

Properties: Oktahidrál crystals are typically colorless or pale-colored, depending on the parent salt. They are soluble in water, with the eight water molecules forming a hydration shell around the ions. Dehydration by heating yields the anhydrous salt MX.

Synthesis: In demonstrations, oktahidrál can be prepared by slow evaporation of an aqueous solution of MX at modest temperature, followed by controlled cooling to promote crystal formation and hydration.

Applications and limitations: Primarily used in teaching to discuss hydration numbers, crystal water, and thermodynamics. It is not widely used in industry due to the instability or rarity of stable octahydrates for many salts.

See also: Hydrates, Octahydrate, Crystal water, Coordination chemistry.