Overview

Telluric acid is the inorganic oxyacid of tellurium with the empirical formula H6TeO6. It is an oxygen-rich, crystalline acid that behaves as a weak acid in water and is the precursor to a family of salts called tellurates. For a concise definition see chemical compound.

Structure and chemical characteristics

Chemically, telluric acid contains hydrogen and tellurate-derived units; the bulk solid can be described as containing Te in an octahedral coordination of oxygen atoms. The acid contains hydrogen atoms bonded in a manner that gives rise to acidic behavior when dissolved, and the tellurate anion is commonly represented by TeO6(6-) cores. Basic elemental components include hydrogen and tellurium-based oxyanions such as the tellurate species; the concept of discrete ions is useful for describing its salts.

Preparation

Telluric acid can be prepared by oxidizing lower tellurium oxides with strong oxidants. Typical laboratory oxidizing agents used to convert tellurium dioxide into the higher-oxygen acid include strong oxidizers such as hydrogen peroxide or chromium(VI) reagents. Heating and careful control of conditions may be required to obtain the hydrated acid rather than related oxides.

Reactions and practical uses

As a weak acid it reacts with bases to form tellurate salts: reaction with strong bases produces tellurate anions and corresponding cations. Telluric acid is also an oxidizing agent in some chemical contexts; it can act as an electron acceptor in reactions where tellurium is reduced. Heating or dehydration of telluric acid can yield lower oxygen-content materials such as tellurium trioxide. It is commonly used as a reagent to prepare other tellurate salts, for example sodium tellurate and related compounds.

History, nomenclature and notable distinctions

The name "telluric" derives from tellurium, a metalloid discovered in the 18th century. Unlike many common oxyacids of lighter elements, a simple metatelluric acid of formal formula H2TeO4 is not a stable, isolable compound in standard conditions; statements that a distinct H2TeO4 exists are not supported by typical inorganic chemistry texts. Telluric acid is often discussed alongside other tellurium oxides and oxyacids to distinguish oxidation states and coordination geometries.

Safety and handling

Telluric acid and its concentrated solutions should be handled with appropriate laboratory precautions. As with many oxidizing and metal-containing acids, wearing gloves and eye protection and working in a fume hood are recommended. For more about its oxidative character see general references to oxidizing agents.

  • Related topics: preparation methods and reagent grades (overview).
  • Comparisons with other tellurium oxyacids and oxides (tellurate chemistry).