tellurite

Tellurite refers to the tellurite anion TeO3^2− and to salts that contain this anion. The ion features tellurium in the +4 oxidation state coordinated to three oxygens, and it is the conjugate base of tellurous acid, H2TeO3. In aqueous solution the system is pH-dependent, with H2TeO3 forming under mildly acidic conditions and TeO3^2− predominating in neutral to basic solutions.

Chemistry and properties: Tellurite is a weak reducing agent that can be oxidized to tellurate (TeO4^2−, tellurate) under stronger oxidizing conditions, and it can be reduced to elemental tellurium or to TeO2. Common tellurite salts include sodium tellurite Na2TeO3 and potassium tellurite K2TeO3, which are typically white to pale yellow solids. Many tellurites are water-soluble, though some transition-metal tellurites exhibit lower solubility. In solution, equilibria between TeO3^2− and H2TeO3 govern speciation with pH.

Preparation: Tellurite salts are often prepared by dissolving TeO2 in hot alkali to form Na2TeO3 or K2TeO3, which can be crystallized or used as solutions. Acidification yields tellurous acid, H2TeO3, enabling retrieval or interconversion of species as needed.

Applications and occurrence: Potassium tellurite is widely used in microbiology as a selective agent in culture media to isolate certain bacteria, notably Corynebacterium diphtheriae. Tellurite compounds also serve as reagents in inorganic synthesis and as precursors for tellurium-containing materials in research and industry.

Safety: Tellurite compounds are toxic and should be handled with appropriate safety precautions. They can be irritants and pose health risks if inhaled, ingested, or absorbed; disposal should follow relevant regulatory guidelines.