Sodium tetrathionate is a

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

and

tetrathionate The tetrathionate anion, , is a sulfur oxoanion derived from the compound tetrathionic acid, H2S4O6. Two of the sulfur atoms present in the ion are in oxidation state 0 and two are in oxidation state +5. Alternatively, the compound can be viewed ...

with the formula Na₂S₄O₆^.H₂O. The salt normally is obtained as the

dihydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

( = 2). It is a colorless, water-soluble solid. It is a member of the polythionates, which have the general formula (SO₃)₂sup>2-. Other members include trithionite ( = 1), pentathionate ( = 3), hexathionate ( = 4). Sodium tetrathionate is formed by the oxidation of

sodium thiosulfate Sodium thiosulfate (sodium thiosulphate) is an inorganic compound with the formula . Typically it is available as the white or colorless pentahydrate, . The solid is an efflorescent (loses water readily) crystalline substance that dissolves well in ...

(Na₂S₂O₃), e.g. by the action of iodine: :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: :2 NaHSO₃ + S₂Cl₂ → Na₂S₄O₆ + 2 HCl The ion has ideal C₂ symmetry, like H₂S₂. The S-S-S

dihedral angle A dihedral angle is the angle between two intersecting planes or half-planes. In chemistry, it is the clockwise angle between half-planes through two sets of three atoms, having two atoms in common. In solid geometry, it is defined as the un ...

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. EntryWithCollCode40833

References

Tetrathionates {{inorganic-compound-stub