Caesium tetroxide

Of particular interest is Caesium Chlor-ruthenite, Cs,.RuC]6.H20, which Howe4 obtained by the action of hydrochloric acid on ruthenium tetroxide and subsequent addition of caesium chloride to the solution. The salt is precipitated as a dark brown powder, fairly soluble in water and hydrochloric acid, exhibiting the chemical reactions of a trivalent ruthenium salt. Howe also describes an isomeride of this salt, which lie termed, in accordance with Werner s nomenclature, Caesium Aquo-chlor-ruthenate [vide infra). 

Oxychlorides.—When ruthenium tetroxide is covered with water, to which caesium chloride acidulated with hydrochloric acid is subsequently added, caesium oxychlor-mthenate,3 Cs2Ru02C14 or 2CsCl.RuOCl2, is formed. On crystallisation dark purple isometric octahedra, cubes, and rhombic dodecahedra separate out. These are soluble in cold hydrochloric acid, from which they may be recrystallised unchanged. 

Ruthenium tetroxide dissolves to a slight extent in water. It is also soluble in caustic alkali, from which solutions a black precipitate of finely divided ruthenium is obtained on addition of alcohol.2 Both the aqueous solution and the pure substance itself possess an odour resembling that of ozone. Its vapour, however, is not poisonous like that of the corresponding tetroxide of osmium. In contact with alcohol the solid tetroxide is reduced with explosive violence.3-4 When covered with water, to which a concentrated solution of caesium chloride is subsequently added and a little hydrochloric acid, ruthenium tetroxide is gradually converted into the oxy-salt, Cs2Ru02CI4. The corresponding rubidium salt has likewise been prepared.3... 

It is interesting to note, in passing, that a similar reaction applied to ruthenium tetroxide led Howe (see p. 143) to discover the oxychlor-ruthenates of caesium and rubidium. 

Hexanitrato Complexes. Alkali metal and ammonium hexanitrato complexes, M2Th(N03)e (M = Rb, Cs, NH4), crystallise from nitric acid solutions containing the appropriate cation and thorium nitrate [1,3 to 7,13]. The caesium salt is also obtained when (N02)2Th(N03)e is reacted with CSNO3. The nitronium complex, (N02)2Th(N03)e, is conveniently obtained by addition of chlorine nitrate to thorium tetrachloride [8] or by the addition of dinitrogen pentoxide to thorium tetranitrate tetrahydrate in anhydrous nitric acid [23]. Treatment with dinitrogen tetroxide results in the formation of (N0)2Th(N03)e [8]. 

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