Cadmium Nitrate, Cd(NO₃)₂

The tetrahydrate, Cd(NO₃)₂.4H₂O, crystallises in mixed prisms and needles from solutions of cadmium nitrate at ordinary temperatures. It is deliquescent, has a density of 2.450 at 14° C. or 2.460 at 20° C., melts at 59.5° C., and boils at about 132° C. The latter solution remains clear till about three-quarters of the water is lost. According to Ditte, some nitric acid is also lost and a basic salt remains. A red heat finally decomposes the salt into crystalline cadmium oxide.

The solubility of the tetrahydrate varies from 52.31 parts of Cd(NO₃)₂ in 100 parts of solution at 0° C. to 76.54 parts at 59.5° C. At lower temperatures a heptahydrate separates from the solution - its solubility varies from 37.37 at -13° C. to 52.73 at +1° C.

[Cd(NO₃)₂.4H₂O]+400Aq. = Cd(NO₃)₂.Aq.-5.04 Cal.

Vasilieff obtained anhydrous cadmium nitrate, melting at about 350° C. and dissolving in water with much evolution of heat, by evaporating the hydrated salt, and an octahydrate by crystallisation at low temperatures. He could not obtain a di- or hexa-hydrate.

The basic nitrates, Cd(OH)(NO₃).H₂O, 12CdO.N₂O₅.11H₂O, 2CdO.N₂O₅.3H₂O, and 5CdO.2N₂O₅.8H₂O, have been described.

Bulky anhydrous crystals of the hexammoniate, Cd(NO₃)₂.6NH₄, were prepared by passing ammonia gas into a solution of cadmium nitrate in ammonia solution. Its dihydrate was obtained by cooling a solution of cadmium nitrate in 20 per cent, ammonia solution. It melts when heated, evolving a little water, and then blackens with a slight explosion.