9120. Telluric(VI) Acid

Nomenclature

CAS number: 7803-68-1
Orthotelluric acid.
H6O6Te; mol wt 229.64.
H 2.63%, O 41.80%, Te 55.57%.
Te(OH)6.

Description and references

Most stable form. Prepd by oxidizing tellurium or its dioxide with chromic acid or potassium permanganate in nitric acid: Staudenmaier, Z. Anorg. Chem. 10, 189 (1895); Mathers et al., Inorg. Synth. 3, 145 (1950); from tellurium by oxidation with chloric acid: Meyer, Franke, Z. Anorg. Allg. Chem. 193, 191 (1930); Meyer, Holowatyi, Ber. 81, 119 (1948); Fehér in Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) pp 451-453°. Forms polymetatelluric acid (H2TeO4)n when heated in air at 100-200°; n approx 11. Concd soln of polymerized form called allotelluric acid; formed when orthotelluric acid is heated in a sealed tube and dissolves in its water of constitution. Review: Datton, Cooper, Chem. Rev. 66, 657-675 (1966).

Properties

White solid; dimorphic: monoclinic, d 3.068; cubic, d 3.163: Avinens, Petit, C. R. Seances Acad. Sci. Ser. C 266, 981 (1968). Crystallizes as tetrahydrate at temp below 10°. Very weak acid: K1 = 2 × 10-8; K2 = 1 × 10-11. Soly in water about 33% at 30°: Mylius, Ber. 34, 2208 (1901). Strong tendency to polymerize (like stannic acid) as the mol wt increases the soly becomes less and less and aq solns become truly colloidal. Sparingly sol in concd nitric acid. Soly in dil nitric acid: Inorg. Syn. (loc. cit.).