Perxenate

The perxenates are salts of perxenic acid, H₄XeO₆. The acid and the anion XeO₆⁴⁻ are both strong oxidizing agents, and the acid can be formed by dissolving xenon tetroxide, XeO₄, into water, like most preparations. The sodium and potassium salts are soluble, but the barium salt may form a marvellous display of xenon trapped in an insoluble crystal.
Barium perxenate is used as starting material for the synthesis of xenon tetroxide (XeO₄) by mixing it with concentrated sulfuric acid, when the following reaction occurs:

: Ba₂XeO₆(s) + 2H₂SO₄(aq) → H₄XeO₆(aq) + 2BaSO₄(s).

The reaction is similar to that of barium peroxide with concentrated sulfuric acid to produce hydrogen peroxide, the standard laboratory way of preparation. Solubility trends and characteristics of perxenates follow closely that of carbonates (most are insoluble).