Potassium Nitrosochlorosmate, K₂Os(NO)Cl₅

Potassium Nitrosochlorosmate, K₂Os(NO)Cl₅, may be readily obtained by boiling potassium osminitrite with concentrated hydrochloric acid:

2K₂Os(NO₂)₅ + 10HCl = 2K₂Os(NO)Cl₅ + 3NO + 5NO₂ + 5H₂O.

The salt yields orthorhombic crystals isomorphous with the corresponding nitrosochlor-ruthenate. It is very stable for a compound of osmium. Its aqueous solution is quite stable, and even nitric acid does not attack the salt as vigorously as usual.