Sodium tellurite

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Sodium tellurite
Names
Other names
Sodium Tellurite IV, Tellurous acid disodium salt
Identifiers
3D model (
JSmol
)
ChemSpider
ECHA InfoCard
 100.030.231 Edit this at Wikidata
EC Number
  • 233-268-4
RTECS number
  • WY2450000
UNII
UN number 3288
  • InChI=1S/2Na.H2O3Te/c;;1-4(2)3/h;;(H2,1,2,3)/q2*+1;/p-2 checkY
    Key: VOADVZVYWFSHSM-UHFFFAOYSA-L checkY
  • InChI=1/2Na.H2O3Te/c;;1-4(2)3/h;;(H2,1,2,3)/q2*+1;/p-2
    Key: VOADVZVYWFSHSM-NUQVWONBAS
  • [Na+].[Na+].[O-][Te]([O-])=O
Properties
Na2TeO3
Molar mass 221.57774 g/mol
Appearance white crystals, powder
Density 6.245 g/cm3
Melting point 710 °C (1,310 °F; 983 K)
soluble
greater than or equal to 100 mg/mL at 68°F
Structure
rhombic
Hazards
GHS labelling:
GHS06: Toxic
Danger
H300, H301, H311, H330, H331
P260, P261, P264, P270, P271, P280, P284, P301+P310, P302+P352, P304+P340, P310, P311, P312, P320, P321, P322, P330, P361, P363, P403+P233, P405, P501
Lethal dose or concentration (LD, LC):
83 mg/kg (rat, oral)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Not to be confused with Sodium telluride.

Sodium tellurite is an inorganic

anode slimes
and is a precursor to tellurium.

Preparation

The main source of tellurium is from copper anode slimes, which contain precious metals as well as various tellurides. These slimes are roasted with sodium carbonate and oxygen to produce sodium tellurite.[1]

Ag2Te + Na2CO3 + O2 → 2Ag + Na2TeO3 + CO2 (400–500 °C)

This is a reaction with silver telluride. The telluride is oxidized to tellurite and the silver(I) is reduced to silver.

Purification

The electrolysis of a tellurite solution yields purified tellurium.[1]

Anode: 4OH− → 2H2O + O2 + 4e−
Cathode: TeO32− + 3H2O + 4e− → Te + 6OH−

Structure and properties

Tellurium has properties similar to sulfur and selenium. In the anhydrous form Na2TeO3 the tellurium atoms are 6 coordinate, three Te-O at 1.87 

Å and the O-Te-O angle is close to 99.5°.[3] The tellurite anion is a weak base. Sodium tellurite would be similar to sodium selenite and sodium sulfite
. Sodium tellurite is both a weak oxidizing agent and a weak reducing agent.

Tellurite-related reactions

H2TeO3 → H+ + HTeO3− pK 2.48

Telluric acid loses a proton at this pKa.

HTeO3− → H+ + TeO32− pK 7.7

Hydrogen tellurite loses a proton at this pKa to become the tellurite ion. This would happen in the reaction of tellurous acid with sodium hydroxide to make sodium tellurite.

TeO2 + 2OH− → TeO32− + H2O

This is the reaction of tellurium dioxide with a base to make a tellurite salt.

Applications

Sodium tellurite improves the corrosion resistance of electroplated nickel layers. Solutions of sodium tellurite are used for black or blue-black coatings on iron, steel, aluminum, and copper. In microbiology, sodium tellurite can be added to the growth medium to isolate bacteria with an inherent physiological resistance to its toxicity.[4]

References

  1. ^
    ISBN 0-12-352651-5
    .
  2. ISSN 0025-5408
    .
  3. doi:10.1107/S0567740879006403
    .
  4. doi:10.1016/S0014-5793(03)01180-3
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