Colloidal Ruthenium

Ruthenium may be obtained in the colloidal condition, as a Colloidal Ruthenium, by reduction of its salts in aqueous solution by hydrazine hydrate in the presence of gum acacia. Other reducing agents may be employed for the same purpose, such as acrolein.

Ruthenium Sponge results on ignition of ammonium chlor-ruthenate. It readily dissolves in a solution of hydrogen chloride saturated with chlorine yielding halogen derivatives. Hydrobromic acid saturated with bromine likewise effects the solution of ruthenium sponge.

Explosive Ruthenium is obtained by dissolving an alloy of the metal with excess of zinc in hydrochloric acid. The zinc passes into solution, leaving metallic ruthenium as a finely divided, explosive residue. Unlike rhodium and iridium, Colloidal Ruthenium is explosive even when prepared in the entire absence of air. It seems hardly possible, therefore, that the same explanation for the explosivity can apply as for the first two metals. Perhaps Bunsen's original explanation is the correct one, namely, that an unstable modification or allotrope is first formed, and that this is converted into the stable variety with considerable heat evolution.