They can also be generated directly from iodates by treatment with other strong oxidizing agents such as hypochlorites: NaIO 3 sodium iodate + Cl 2 + 4 NaOH ⟶ Na 3 H 2 IO 6 + 2 NaCl + H 2 O {\displaystyle {\ce {{\overset {sodium\ iodate}{NaIO3}}+Cl2{}+4NaOH->Na3H2IO6{}+2NaCl{}+H2O}}} NaI + 4 Br 2 + 10 NaOH ⟶ Na 3 H 2 IO 6 + 8 NaBr + 4 H 2 O {\displaystyle {\ce {NaI + 4 Br2 + 10 NaOH -> Na3H2IO6 + 8 NaBr + 4 H2O}}} Periodates were discovered by Heinrich Gustav Magnus and C. F. Ammermüller; who first synthesised periodic acid in 1833. [1] Synthesis [ edit ] NaIO 3 + NaOCl sodium hypochlorite ⟶ NaIO 4 + NaCl {\displaystyle {\ce {NaIO3{}+{\overset {sodium\ hypochlorite}{NaOCl}}->NaIO4{}+NaCl}}} Forms and interconversion [ edit ]

Metaperiodates are typically prepared by the dehydration of sodium hydrogen periodate with nitric acid, [2] or by dehydrating orthoperiodic acid by heating it to 100 °C under vacuum. Periodate can exist in a variety of forms in aqueous media, with pH being a controlling factor. Orthoperiodate has a number of acid dissociation constants. [5] [6] H 5 IO 6 ↽ − − ⇀ H 4 IO 6 − + H + {\displaystyle {\ce {H5IO6 <=> H4IO6- + H+}}} p K a = 3.29 H 4 IO 6 − ↽ − − ⇀ H 3 IO 6 2 − + H + {\displaystyle {\ce {H4IO6- <=> H3IO6Na 3 H 2 IO 6 + 2 HNO 3 ⟶ NaIO 4 + 2 NaNO 3 + 2 H 2 O {\displaystyle {\ce {Na3H2IO6 + 2 HNO3 -> NaIO4 + 2 NaNO3 + 2 H2O}}} H 5 IO 6 ⟶ HIO 4 + 2 H 2 O {\displaystyle {\ce {H5IO6 -> HIO4 + 2 H2O}}} H 5 IO 6 + H + + 2 e − ⟶ IO 3 − + 3 H 2 O {\displaystyle {\ce {H5IO6 + H+ + 2e- -> IO3- + 3 H2O}}} E° = 1.6 V [4] Modern industrial scale production involves the electrochemical oxidation of iodates, on a lead dioxide ( PbO 2) anode, with the following standard electrode potential: Classically, periodate was most commonly produced in the form of sodium hydrogen periodate ( Na 3H 2IO 6). [2] This is commercially available, but can also be produced by the oxidation of iodates with chlorine and sodium hydroxide. [3] Or, similarly, from iodides by oxidation with bromine and sodium hydroxide: In this regard it is comparable to the tellurate ion from the adjacent group. It can combine with a number of counter ions to form periodates, which may also be regarded as the salts of periodic acid.

Periodate / p ə ˈ r aɪ . ə d eɪ t/ is an anion composed of iodine and oxygen. It is one of a number of oxyanions of iodine and is the highest in the series, with iodine existing in oxidation state +7. Unlike other perhalogenates, such as perchlorate, it can exist in two forms: metaperiodate IO −