Nickel(II) selenate

Nickel(II) selenate is a selenate of nickel with the chemical formula NiSeO₄.

Preparation

Nickel(II) selenate can be produced by the reaction of nickel(II) carbonate and selenic acid.

$\mathrm{N}\mathrm{i}\mathrm{C}{\mathrm{O}}_{\mathrm{3}}\mathrm{+}{\mathrm{H}}_{\mathrm{2}}\mathrm{S}\mathrm{e}{\mathrm{O}}_{\mathrm{4}}\mathrm{\to }\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{e}{\mathrm{O}}_{\mathrm{4}}\mathrm{+}{\mathrm{H}}_{\mathrm{2}}\mathrm{O}\mathrm{+}\mathrm{C}{\mathrm{O}}_{\mathrm{2}}\mathrm{\uparrow }$

Properties

Nickel(II) selenate hexahydrate is a green solid. It is tetragonal, space group P4₁2₁2 (No. 92). At 100 °C, nickel(II) selenate hexahydrate slowly loses water to the tetrahydrate, with space group P2₁/n (No. 14). At 510 °C, nickel(II) selenate decomposes directly into nickel selenite, which on further heating decomposes into nickel(II) oxide and selenium dioxide.

$\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{e}{\mathrm{O}}_{\mathrm{4}}\mathrm{\cdot }\mathrm{6}{\mathrm{H}}_{\mathrm{2}}\mathrm{O}\underset{-H_{2}O}{\overset{100{}^{\circ }C}{\to }}\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{e}{\mathrm{O}}_{\mathrm{4}}\mathrm{\cdot }\mathrm{4}{\mathrm{H}}_{\mathrm{2}}\mathrm{O}\underset{-H_{2}O}{\overset{300{}^{\circ }C}{\to }}\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{e}{\mathrm{O}}_{\mathrm{4}}\mathrm{\cdot }{\mathrm{H}}_{\mathrm{2}}\mathrm{O}\underset{-H_{2}O}{\overset{390{}^{\circ }C}{\to }}\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{e}{\mathrm{O}}_{\mathrm{4}}\underset{-O_2}{\overset{510{}^{\circ }C}{\to }}\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{e}{\mathrm{O}}_{\mathrm{3}}\underset{-Se{O}_2}{\overset{690{}^{\circ }C}{\to }}\mathrm{N}\mathrm{i}\mathrm{O}$

It and potassium selenate are cooled and crystallized in hot aqueous solution to obtain the blue-green [Ni(H₂O)₆](SeO₄)₂.

${\mathrm{K}}_{\mathrm{2}}\mathrm{S}\mathrm{e}{\mathrm{O}}_{\mathrm{4}}\mathrm{+}\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{e}{\mathrm{O}}_{\mathrm{4}}\mathrm{+}\mathrm{6}{\mathrm{H}}_{\mathrm{2}}\mathrm{O}\mathrm{\to }{\mathrm{K}}_{\mathrm{2}}\mathrm{[}\mathrm{N}\mathrm{i}\mathrm{(}{\mathrm{H}}_{\mathrm{2}}\mathrm{O}{\mathrm{)}}_{\mathrm{6}}\mathrm{]}\mathrm{(}\mathrm{S}\mathrm{e}{\mathrm{O}}_{\mathrm{4}}{\mathrm{)}}_{\mathrm{2}}$