Compound of nickel
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Chemical compound
Nickel(II) perchlorate is a collection of inorganic compounds with the chemical formula of . Its colors of these solids vary with the degree of hydration. For example, the hydrate forms cyan crystals, the pentahydrate forms green crystals, but the hexahydrate (Ni(ClO4)2·6H2O) forms blue crystals. Nickel(II) perchlorate hexahydrate is highly soluble in water and soluble in some polar organic solvents.
Preparation.
Aqueous solutions of nickel(II) perchlorate can be obtained by treating nickel(II) hydroxide, nickel(II) chloride or nickel(II) carbonate with perchloric acid.
Ni(OH)2 + 2HClO4 + 4H2O → Ni(ClO4)2·6H2O
Two hydrates have been characterized by X-ray crystallography: the hexahydrate and the octahydrate. Several other hydrates are mentioned including the pentahydrate, which is claimed to crystallize at room temperature, the nonahydrate, which is claimed to crystallize at −21.3 °C, a tetrahydrate, and a monohydrate. 
The yellow anhydrous product is obtained by treating nickel(II) chloride with chlorine trioxide. As deduced by X-ray crystallography, Ni resides in a distorted octahedral environment and the perchlorate ligands bridge between the Ni(II) centers.
Applications.
Nickel(II) perchlorates has few practical uses.
References.
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