Ruthenium Nitrosotrihydroxide, Ru(NO)(OH)₃

Ruthenium Nitrosotrihydroxide, Ru(NO)(OH)₃, is readily obtained by addition of the requisite quantity of potassium hydroxide to a solution of potassium nitrosochlor-ruthenate, K₂Ru(NO)Cl₅ or 2KCl.Ru(NO)Cl₃, at the boiling-point.

2KCl.Ru(NO)Cl₃ + 3KOH = 5KCl + Ru(NO)(OH)₃.

The liquid, which had a reddish blue colour, becomes colourless, a clear brown, gelatinous precipitate of the hydroxide separating out. Since the hydroxide is soluble in excess of the potash, yielding a brown solution, care must be taken to add only the theoretical quantity required. Thorough washing with boiling water, in which the precipitate is insoluble, is desirable to remove all traces of potassium chloride.

When dissolved in potassium hydroxide solution and reduced with formaldehyde, a mixture of hydrates is obtained. Addition of hydrochloric acid and potassium chloride and subsequent evaporation results in brown crystals of potassium chlor-ruthenite, K₂RuCl₅, and red crystals of Ru₂(NO)Cl.3KCl.4HCl separating out. These differ in solubility, the former being more rapidly dissolved by cold water than the latter ; the isolation of each in a pure state is thus easy.

When ruthenium nitrate is boiled with hydrochloric acid and evaporated at 120° C., a Nitrosochloride, RuCl₃.NO.H₂O, is obtained as a red crystalline mass. On recrystallisation a pentahydrate is formed, RuCl₃.NO.5H₂O, as dichroic triclinic crystals, which effloresce in dry air.

The nitrosochloride is also obtained by boiling for several days with aqua regia the precipitate formed on addition of dilute alcoholic potash to ruthenium tetroxide.

Several other complex nitroso derivatives of ruthenium have been prepared, namely:

Ru₂(NO)H₂(OH)Cl₂, Ru₂(NO)H₂(OH)₃, Ru₂(NO)H₂Cl₃.2HCl, and Ru₂(NO)H₂Cl₃.(NH₃)₆.2HCl; but for accounts of these the reader is referred to the original memoir.