title: Tellurite
text: # Tellurite
  
  The tellurite ion is $TeO^{2−}$ $_3.$ A tellurite (compound), for example sodium tellurite, is a compound that contains this ion. They are typically colorless or white salts, which in some ways are comparable to sulfite. A mineral with the formula $TeO_2$ is called tellurite.
  
  ## Structure and reactions
  
  Tellurite dianion is pyramidal, like selenite and sulfite. The anion has $C_{3v}$ symmetry.
  
  Tellurites can be reduced to elemental tellurium by electrolysis or a strong reducing agent. When fused with nitrate salts, tellurite salts oxidize to tellurates $(TeO^{2−}$ $_4).$
  
  Upon acidification of aqueous solutions of tellurite salts, solid hydrated tellurium dioxide $(TeO_2)$ precipitates. This reaction allows the separation of tellurium from selenium since selenous acid remains soluble at low pH. The intermediate in the protonation occurs at oxygen to give $[TeO_2(OH)]^−.$
  
  ## Uses
  
  Potassium tellurite $(K_2TeO_3)$ is used together with agar as part of a selective medium for growth of some bacteria (Clauberg medium). Corynebacteria and some other species reduce $TeO^{2−}$ $_3$ to elemental Te, which stains the bacteria black.
  
  