S4O62

S4O6^2−, commonly called tetrathionate, is an oxoanion of sulfur with the formula S4O6^2−. It consists of a four-sulfur chain capped by oxygen-containing groups and carries a 2− overall charge. In aqueous solution it is typically formed by partial oxidation of thiosulfate or by redox processes involving sulfur species. It is encountered in laboratory settings, natural waters, and certain industrial contexts.

Structure and properties: The tetrathionate ion has a linear or near-linear chain of four sulfur atoms with six oxygens arranged around the terminal sulfurs. The two inner sulfur atoms are bonded within the chain, while the terminal sulfur atoms are linked to oxygens as in thionate-like groups. The ion is soluble in water and is relatively stable under moderate pH, though it can participate in redox chemistry under more extreme conditions.

Formation and occurrence: In aqueous environments, oxidants such as chlorine, iodine, hypochlorite, or dissolved oxygen can convert thiosulfate to tetrathionate. It also arises as an intermediate in microbial sulfur metabolism and in natural sulfur cycles, where various bacteria catalyze redox transformations involving tetrathionate.

Chemical reactions: Tetrathionate can be further oxidized to sulfate in oxidizing environments and reduced to sulfur-containing species such as sulfite or sulfide under reducing conditions. It participates in redox cycling in natural waters and in certain microbial pathways, where it may serve as an electron sink or source depending on the organism and conditions.

Applications: In analytical chemistry, tetrathionate is used in iodometric-type redox assays and related methods. In microbiology, tetrathionate-containing media, such as tetrathionate broth, are used to enrich and detect certain pathogens by exploiting the selective effects of tetrathionate on microbial growth.