Telluric acid

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Structural formula
Structure of telluric acid
Surname Telluric acid
other names

Orthotelluric acid

Molecular formula H 6 TeO 6
Brief description

colorless powder

External identifiers / databases
CAS number 7803-68-1
EC number 232-267-6
ECHA InfoCard 100.029.334
PubChem 62686
Wikidata Q425172
Molar mass 229.66 g mol −1
Physical state



3.16 g cm −3

Melting point

136 ° C

pK s value

7.70 (pK s1 ); 10.95 (pK s2 )


moderate in water (100 g l −1 at 20 ° C)

safety instructions
GHS labeling of hazardous substances
07 - Warning


H and P phrases H: 332
P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Telluric acid is a very weak acid of tellurium . The low acidity is due to the structure. The negative charge in the anion cannot be delocalized . Tellurium has the VI oxidation state in the compound.


Telluric acid is obtained from finely divided tellurium and aqueous chloric acid solution, by oxidizing tellurium dioxide with potassium permanganate in nitric acid , by oxidizing tellurium or tellurium dioxide with hydrogen peroxide or by oxidizing tellurium with nitric acid and chromium trioxide .


Telluric acid has an octahedral structure and is therefore also called ortho telluric acid. It forms colorless and water-soluble crystals . Since the 1st dissociation stage of telluric acid is already very small and the last (6th) is therefore vanishingly small, most tellurates (salts) only exist as hydrogen tellurates , but there is silver tellurate, Ag 6 TeO 6 . The anhydride of telluric acid, tellurium trioxide (TeO 3 ), is a yellow crystal powder . Telluric acid and (water-soluble) tellurates are poisonous and have a very strong oxidizing effect. Telluric acid comes in a monoclinic modification and a cubic modification. Large crystals are usually monoclinic, while the microcrystalline powder often consists of a mixture of both forms. When heated, the compound turns into solid, water-insoluble polymetatelluric acid between 100 and 220 ° C, which breaks down into tellurium trioxide above 220 ° C and into tellurium dioxide and oxygen above 400 ° C. Telluric acid melts in a closed tube at about 136 ° C to form a concentrated aqueous solution of polymetatelluric acid and some ortho acid.

Individual evidence

  1. ^ Frank C. Mathers et al .: Telluric acid . In: Ludwig F. Audrieth (Ed.): Inorganic Syntheses . tape 3 . McGraw-Hill, Inc., 1950, pp. 145-147 (English).
  2. Claudia Synowietz (Ed.): Paperback for chemists and physicists . founded by Jean d'Ans, Ellen Lax. 4th edition. Volume II: Organic Compounds . Springer, Berlin 1983, ISBN 3-540-12263-X .
  3. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 .
  4. ^ A b A. F. Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , p. 634.
  5. a b c Datasheet Telluric acid from Sigma-Aldrich , accessed on October 03, 2016 ( PDF ).
  6. G. Brauer (Ed.), Handbook of Preparative Inorganic Chemistry 2nd ed., Vol. 1, Academic Press 1963, pp. 451-3.
  7. Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume I, Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 , p. 439.