Potassium Osmiamate, OsNO₃K

Potassium Osmiamate, OsNO₃K, may be obtained by the action of ammonia on a cold solution of osmium tetroxide in potassium hydroxide. Thus:

OsO₄ + KOH + NH₃ = OsNO₃K + 2H₂O.

The salt crystallises in orange-yellow, tetragonal pyramids, which partially decompose upon recrystallisation, becoming darker in colour. When heated, nitrogen gas is evolved.

The corresponding barium, silver, and sodium salts have been prepared.