Water of crystallization degree of hydration can be critical to the resulting chemical properties. For example, anhydrous RhCl is not soluble in water and is relatively useless in organometallic chemistry whereas RhCl•3HO is versatile. Similarly, hydrated AlCl is a poor Lewis acid and thus inactive as a catalyst for Friedel-Crafts reactions. Samples of AlCl must therefore be protected from atmospheric moisture to preclude the formation of hydrates. Crystals of hydrated copper(II) sulfate consist of [Cu(HO)] centers linked to SO ions. Copper is surrounded by six oxygen atoms, provided by two different sulfate groups and four molecules of water. A fifth water resides elsewhere
Heavy water not melt in ice-cold normal water. An early experiment reported not the "slightest difference" in taste between ordinary and heavy water. However, rats given a choice between distilled normal water and heavy water were able to avoid the heavy water based on smell, and it may have a different taste. No physical properties are listed for "pure" semi-heavy water, because it is unstable as a bulk liquid. In the liquid state, a few water molecules are always in an ionised state, which means the hydrogen atoms can exchange among different oxygen atoms. Semi-heavy water could, in theory, be created via