Hydrated Ruthenium Sesquioxide, Ru₂(OH)₆

Hydrated Ruthenium Sesquioxide, Ru₂O₃.3H₂O or Ru₂(OH)₆, was prepared by Gutbier and Ransohoff by addition of sodium hydroxide to an aqueous solution of ruthenium sesquichloride, Ru₂Cl₆. A blackish brown amorphous precipitate was obtained which was dried in a vacuum desiccator over sulphuric acid. Analysis yielded figures agreeing fairly well with the formula given above, but it was not found possible to remove the last traces of alkali, even by washing with very dilute hydrochloric acid. Ignition in a current of hydrogen yields the pure metal.

Ruthenium hydroxide is obtained in colloidal form by reducing an aqueous solution of potassium chlor-ruthenite, K₂RuCl₅, by hydrazine sulphate in the presence of gum acacia, which serves as a protective colloid, preventing the coagulation of the hydroxide.