Palladous Nitrate, Pd(NO₃)₂

Palladous Nitrate, Pd(NO₃)₂, may be obtained by dissolving the metal in nitric acid of density 1.35 to 1.4, and cooling the concentrated solution, when the salt crystallises out in brownish yellow, orthorhombic crystals. These are deliquescent, and readily dissolve in water, yielding a solution that is not very stable. When heated, the crystals decompose, yielding palladous oxide.

Although Palladous Nitrite has not been isolated, double salts of general formula 2MNO₂.Pd(NO₂)₂ or M₂Pd(NO₂)₄ have been prepared. The most important of these is:

Potassium Pallado-nitrite, K₂Pd(NO₂)₄, which is obtained by addition of potassium nitrite to a solution of palladous nitrate or chloride, and subsequent boiling. On crystallisation in the warm the anhydrous salt is obtained, whilst in the cold the dihydrate, K₂Pd(NO₂)₄.2H₂O, separates out as yellow, efflorescent, triclinic prisms. These are readily soluble in water, but less so in an aqueous solution of potassium chloride. The solution does not behave like one of an ordinary palladous salt towards chemical reagents. For example, it is not precipitated by hydrogen sulphide, nor even by mercuric cyanide, until after prolonged boiling, a fact that indicates its complex nature. It is not a simple double nitrite, but a pallado-nitrite in which the palladium occurs, not in the positive, but in the negative radicle.