Potassium Nitrosochloivifuthenate K₂RuCl₅NO

Potassium Nitrosochloivifuthenate or Potassium Ruthenium Nitrosochloride, 2KCl.RuCl₃.NO or K₂RuCl₅NO, is obtained by direct precipitation of concentrated solutions of potassium chloride and ruthenium nitrosochloride ; it also results on evaporation of mixed dilute solutions of the two substances. It yields black orthorhombic crystals which dissolve in water to a reddish violet solution. The aqueous solution is stable, its electric conductivity showing no alteration whatever after standing for two weeks. Its solution apparently contains three ions, namely, К^•, К^•, and RuCl₅.NO''.

This salt is interesting as being the one which led Claus in 1845 to identify ruthenium as a new element. He believed it to be K₂RuCl₃, analogous to potassium chlorplatinate, but Joly showed it to be a nitroso compound. The dihydrate, 2KCl.RuCl₃.NO.2H₂O, is deposited as black, efflorescent crystals when the mother-liquors of the salt are slowly concentrated.

The corresponding bromine and iodine derivatives, namely, 2KBr.RuBr₃.NO and 2KI.RuI₃.NO respectively, have been prepared.