Osmium Nitrite, Os(NO₂)₃

Osmium Nitrite, Os(NO₂)₃, is obtained when barium osminitrite is decomposed with the theoretical amount of dilute sulphuric acid. By operating in the cold the evolution of nitrous fumes may be avoided, and the liquid appears to contain osminitrous acid, H₂Os(NO₂)₅. On concentrating, nitrous fumes are evolved, and osmium nitrite is obtained as a deep brown powder, stable in air.