Sodium tetrathionate dihydrate
Names
IUPAC name
Sodium (sulfonatodisulfanyl)sulfonate dihydrate
Identifiers
3D model (JSmol)
ECHA InfoCard 100.208.917 Edit this at Wikidata
  • InChI=1S/2Na.H2O6S4.2H2O/c;;1-9(2,3)7-8-10(4,5)6;;/h;;(H,1,2,3)(H,4,5,6);2*1H2/q2*+1;;;/p-2
    Key: HAEPBEMBOAIUPN-UHFFFAOYSA-L
  • O.O.[O-]S(=O)(=O)SSS(=O)(=O)[O-].[Na+].[Na+]
Properties
Na2S4O6
Molar mass 306.2665 g/mol (dihydrate)
Appearance white powder
Density 2.1 g/mL (25 °C)
30.6 g/L (20 °C)
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
0
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Sodium tetrathionate is a salt of sodium and tetrathionate with the formula Na2S4O6.xH2O. The salt normally is obtained as the dihydrate (x = 2). It is a colorless, water-soluble solid. It is a member of the polythionates, which have the general formula [Sn(SO3)2]2-. Other members include trithionite (n = 1), pentathionate (n = 3), hexathionate (n = 4).[1]

Sodium tetrathionate is formed by the oxidation of sodium thiosulfate (Na2S2O3), e.g. by the action of iodine:[1]

2 Na2S2O3 + I2 → Na2S4O6 + 2 NaI

The reaction is signaled by the decoloration of iodine. This reaction is the basis of iodometric titrations.

Other methods include the coupling of sodium bisulfite with disulfur dichloride:[1]

2 NaHSO3 + S2Cl2 → Na2S4O6 + 2 HCl

The ion has ideal C2 symmetry, like H2S2. The S-S-S dihedral angle is nearly 90°. The central S-S distance is 2.115 Å, 0.01 Å longer than the two other S-S distances as well as those distances in most polysulfanes.[2]

Structure of tetrathionate as its dihydrated sodium salt.[2]

References

  1. ^ a b c Greenwood, N. N.; Earnshaw, A. (2 January 1991). Chemistry of the Elements - 3rd Edition. Elsevier. doi:10.1016/C2013-0-11881-8. ISBN 978-1-4832-8008-0. OCLC 1040594550. Retrieved 2022-02-15.
  2. ^ a b P. C. Christidis; P. J. Rentzeperis; C. A. Bolos (4 January 1986). "Crystal structure and chirality of sodium tetrathionate dihydrate, Na2S4O6·2H2O". Zeitschrift für Kristallographie. 177 (1–2): 107–p116. Bibcode:1986ZK....177..107C. doi:10.1524/zkri.1986.177.1-2.107.


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