thumb|Structure of the hexathionate dianion.<ref>{{cite journal|volume=27|year=1973|title=Refinement of the Crystal Structure of trans-Dichlorobis(ethylenediamine)cobalt(III) Hexathionate Monohydrate|author=Marøy, Kjartan|journal=Acta Chemica Scandinavica|pages=1705–1716|doi=10.3891/acta.chem.scand.27-1705|doi-access=free}}</ref> '''Polythionates''' are oxyanions with the formula {{chem2|-O3S\sS_{''n''}\sSO3-}} (''n'' ≥ 0). They occur naturally and are the products of redox reactions of thiosulfate. Polythionates are readily isolable, unlike the parent polythionic acids.<ref>{{Greenwood&Earnshaw2nd}}</ref>
==Preparation== Many members of the polythionates have been characterized: dithionate, trithionate, tetrathionate, pentathionate, etc.
These salts are often generated by oxidation of thiosulfate. For example, tetrathionate is obtained by oxidation of thiosulfate ion with iodine (reaction is used in iodometry): :{{chem2|2 S2O3(2−) + I2 → S4O6(2−) + 2 I−}}
More specialized routes involve reactions of sulfur chlorides with bisulfite salts: :{{chem2|SCl2 + 2 HSO3− → [O3SSSO3](2−) + 2 HCl}} :{{chem2|S2Cl2 + 2 HSO3− → [O3SS2SO3](2−) + 2 HCl}} :{{chem2|SCl2 + 2 HS2O3− → [O3SS3SO3](2−) + 2 HCl}} Potassium pentathionate ion has been obtained from {{chem2|SCl2}}, sodium thiosulfate, and potassium acetate. Initially prismatic crystals of potassium tetrathionate appear, then lamellar crystals of potassium pentathionate, from which the influence of tartaric acid makes an aqueous solution of pentathionic acid.<ref>{{cite book|author=P. W. Schenk|chapter=Sulfur, Selenium, Tellurium|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1|pages=401}}</ref>
Potassium hexathionate {{chem2|K2S6O6}} has been synthesized by combining {{chem2|KNO2}} and {{chem2|K2S2O3}} in concentrated HCl at low temperatures.<ref>{{cite book|author=P. W. Schenk|chapter=Sulfur, Selenium, Tellurium|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1|pages=403}}</ref>
==References== {{Reflist}}
Category:Sulfur compounds