Sodium perxenate

Xenon Tetroxide. Xe04, mw 195.30, colorl gas, mp -40° (explds). Prepn is by reacting sodium perxenate with coned sulfuric acid. Compd is v unstable... 

Xe03p2 was the first oxyfluoride of octavalent xenon to be prepared. It was made by reaction of XeFe with sodium perxenate solid at room temperature. Xe03p2 is, like Xe04, sufficiently volatile to distil at 195 K. The much greater volatihty of Xe03p2 as compared to Xe02p2 indicates that the molecule of Xe03p2 is more symmetrical and probably nonpolar (Z>3/,). 

The perxenates are colorless, thermally stable solids. Anhydrous sodium perxenate can be obtained at 373 K. It decomposes at 633 K. The corresponding barium salt decomposes at about 570 K. Perxenate solutions are powerful and rapid oxidizing agents. Xenon(VIII) is reduced to xenon(VI). Oxidation processes in acid media are more effective, but they must be fast enough to compete with decomposition of the perxenate, which is also rapid in acid. 

Hydrolysis of xenon hexafluoride or tetrafluoride with a sodium hydroxide solution results in the precipitation of a stable xenon (VIII) salt, sodium perxenate, Na4XeOe, which on heating does not decompose until around 300°. Similar hydrolysis with potassium hydroxide can yield a yellow precipitate which is a mixed potassium perxenate-xenon trioxide salt, and is explosive even when damp. With more concentrated base, the much more stable hydrated perxenate may be isolated. 

In this procedure, sodium perxenate is precipitated from 1-2 M sodium hydroxide, presumably in accordance with the above equation. The actual stoichiometry with respect to ozone has... 

Freshly precipitated sodium perxenate has 2-8 waters of hydration per xenon. Exhaustive drying at room temperature leaves ca. 0.6 water per xenon. In an earlier publication, drying in vacuum at 110 was recommended to obtain the anhydrous product. This recommendation was based on thermogra imetric studies that indicated the complete loss of water at this temperature. Iore careful investigation has shown, however, that the loss of water is accompanied by loss of several percent of the xenon, leaving a contaminating residue of sodium h droxide. It therefore seems advisable to be content with the slightlj" hydrated product obtainable at room temperature. 

Sodium perxenate may also be prepared without the use of ozone by allowing HXe04 to disproportionate in strong NaOH, but in that case the jdeld cannot exceed 50%. ... 

Sodium perxenate is stable at room temperature, but if left exposed to the air, it may absorb water and carbon dioxide. The salt is soluble in water to the extent of about 0.025 M, and the solutions are basic because of hydrolysis ... 

Solutions of sodium perxenate are very powerful oxidants, and accidental contact with reducing substances should be avoided. A frequent reaction product is xenon trioxide, the hazards of which are detailed in the preceding s Oithesis. ... 

Although a total analysis of sodium perxenate can be devised, two relatively simple analjrses are generally sufficient to characterize the product ... 

Sodium perxenate, first prepared in 1963, has a standard electrode potential estimated to be 3.0 V in acid solution. Without a catalyst and at room temperature it rapidly oxidizes Mn(II) to Mn(VII). In neutral solution it oxidizes Np(IV) and Pu(IV) hydroxides to Np(VI) and Pu(VI). Sodium perxenate decomposes in acid solution ... 

A normal-co-ordinate treatment of Xe02F2 using a modified Urey-Bradley force field has been carried out and the results have been compared with new treatments for XeOp4 and Xe03p2, as well as with force constants reported for other xenon compounds.The results have been set out in Table 2, from which it is evident that, as oxygen atoms are added to Xep2, the Xe—F bond distance decreases while the Xe—O bond distance increases. Aqueous solutions of pure XeOs at concentrations up to 0.1 mol T can be prepared from sodium perxenate by means of a cation-exchange resin. 

It is prepared from barium perxenate or sodium perxenate by reaction with anhydrous sulphuric acid. 

XeO is an unstable gas, exploding even at a low temperature. It is prepared by reaction of anhydrous HjSO with barium perxenate or sodium perxenate. 

Test by oxidation with sodium perxenate to permanganic acid... 

Manganese i salts in dilute acidic solution (sulfuric, perchloric or nitric acid) are immediately oxidized by sodium perxenate to permanganic acid ... 

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