What does dithionic mean?
Dithionic is an adjective used exclusively in chemistry to describe dithionic acid (H₂S₂O₆) and the salts derived from it, known as dithionates. The name reflects the acid's defining feature: two sulfur atoms joined together, each in the +5 oxidation state. Dithionic acid itself can only be obtained in dilute aqueous solution, but its salts — such as sodium and barium dithionate — are stable crystalline solids studied for their unusual resistance to oxidation by many common oxidising agents. The word belongs to a family of sulfur-oxyacid terms distinguished by numerical prefixes (as in thionic, dithionic, trithionic) that signal how many sulfur atoms the acid contains. Outside laboratory and academic writing it is essentially never encountered, so it carries no connotations beyond precise chemical meaning; using it signals familiarity with inorganic nomenclature rather than any stylistic register.
adjectiveOf or relating to dithionic acid (H₂S₂O₆) and its salts; containing sulfur in an intermediate oxidation state characteristic of that acid.
- Relating to or denoting dithionic acid (H₂S₂O₆) or its salts (dithionates).
"The chemist prepared a solution of a dithionic salt to study its oxidation behaviour."
"Barium dithionate was isolated as crystalline needles during the analysis."
"Dithionic compounds are notable for resisting oxidation by mild agents such as chlorine water under some conditions."
Despite the 'di-' prefix suggesting double trouble, dithionic acid's two sulfur atoms sit at a surprisingly tame +5 oxidation state — right in the middle of sulfur's wild range.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of dithionic
The term combines the prefix di- ('two') with the Greek-derived element -thionic, from Greek 'theion', meaning sulfur, plus the adjectival suffix -ic. It was coined in nineteenth-century chemistry when the series of polythionic acids (containing chains of sulfur atoms) was being characterised. Cognate formations include thionic, trithionic, and the corresponding noun dithionate.
Related word forms
How dithionic is actually used
A technical term confined almost entirely to chemistry, appearing chiefly in textbooks and research literature as part of the fixed phrases 'dithionic acid' and 'dithionic salt'. It has no figurative or everyday use.
Easily confused with dithionic
Dithionous refers to dithionous acid (H₂S₂O₄), in which the two sulfur atoms are in a lower oxidation state (+3) than in dithionic acid (+5).
Thionic acids contain one replaceable oxygen replaced by sulfur in a monobasic oxyacid, whereas dithionic specifically denotes the dibasic acid H₂S₂O₆ with two sulfur atoms.