The tellurite ion

Ion

An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

 is TeO₃²⁻. A tellurite (compound) is a compound that contains this ion. An example is sodium tellurite

Sodium tellurite

Sodium tellurite is an inorganic tellurium compound with formula Na2TeO3. It is a water soluble white solid and a weak reducing agent. Sodium tellurite is an intermediate in the extraction of the element, tellurium; it is a mineral obtained from slimes and is a precursor to...

. Tellurites are one of the more stable tellurium compounds, although they can be reduced to elemental tellurium by electrolysis or a strong reducing agent.

Acidified forms

In slightly acidic conditions, hydrogen tellurite ion, HTeO₃⁻, is prevalent; with more acidic conditions tellurous acid

Tellurous acid

Tellurous acid is an inorganic compound with the formula H2TeO3. It is the oxoacid of tellurium. The compound is not well characterized. An alternative way of writing its formula is 2TeO. In principle, tellurous acid would form by treatment of tellurium dioxide with water, i.e. hydrolysis...

, H₂TeO₃, is prevalent. Only in basic conditions is tellurite formed.

Preparation

Most tellurite compounds can be formed by heating the relevant oxide with tellurium dioxide

Tellurium dioxide

Tellurium dioxide is a solid oxide of tellurium. It is encountered in two different forms, the yellow orthorhombic mineral tellurite, β-TeO2, and the synthetic, colourless tetragonal , α-TeO2...

, e.g., Na₂O + TeO₂ →-> Na₂TeO₃.

Uses

Potassium tellurite (K₂TeO₃)is used together with agar as part of a selective medium for growth of some bacteria (Clauberg medium). Corynebacteria and some other species reduce TeO₃^2- to elemental Te, which stains the bacteria black.