Cadmium Nitrite, Cd(NO₂)₂

Pale yellow crystals of anhydrous nitrite, Cd(NO₂)₂, are obtained by triturating cadmium chloride and silver nitrite together, adding water, filtering, and evaporating in vacuo over sulphuric acid. Its decomposition by heat seems to be represented by the two equations

3Cd(NO₂)₂ = 2CdO+Cd(NO₃)₂+4NO;
Cd(NO₂)₂ = CdO+NO+NO₂.

Cadmium nitrate is ionised very distinctly in aqueous solution and tends to form basic salts.

A solution of cadmium nitrite is obtained by interaction between equivalent quantities of barium nitrite and cadmium sulphate in solution. A hygroscopic crystalline mass of the monohydrate, Cd(NO₂)₂.H₂O, has been obtained from such a solution, but, even by careful evaporation, a basic salt is often obtained, and it is difficult to obtain a salt in which the ratio NO₂:Cd is as high as 2:1.

The colourless double salt, KNO₂.Cd(NO₂)₂, and the yellow salts, 2KNO₂.Cd(NO₂)₂ and 4KNO₂.Cd(NO₂)₂, have been prepared crystalline by treating a solution of cadmium acetate with potassium nitrite. The salt 2NH₄.NO₂.Cd(NO₂)₂.H₂O.CdO.2NH₄ has been obtained in transparent rhomboidal prisms by treating a saturated solution of ammonium nitrate with granulated cadmium, and the complex nitrites, 4KNO₂.2Cd(NO₂)₂.Ni(NO₂)₂, 4ThNO₂.2Cd(NO₂)₂.Ni(NO₂)₂, and 2NH₄NO₂.Cd(NO₂)₂.Ni(NO₂)₂, have also been prepared.

Cadmium nitrite also forms the compound Cd(NO₂)₂.2H₂O.C₆H₁₂N₄ with hexamethylenetetramine.