Telluropentathionic Acid, H₂TeS₄O₆

The sodium salt of this acid may be prepared by the action of tellurium dioxide on an aqueous solution of sodium thiosulphate in the presence of hydrochloric acid:

TeO₂ + 4Na₂S₂O₃ + 4HCl = Na₂TeS₄O₆ + Na₂S₄O₆ + 4NaCl + 2H₂O, The salt decomposes in the presence of alkali with separation of tellurium.