Thiosulfuric acid is the inorganic compound with the formula . It has attracted academic interest as a simple, easily accessed compound that is
labile
Lability refers to the degree that something is likely to undergo change. It is the opposite ( antonym) of stability.
Biochemistry
In reference to biochemistry, this is an important concept as far as kinetics is concerned in metalloprotein ...
. It has few practical uses.
Preparation and degradation
The acid cannot be made by acidifying aqueous
thiosulfate
Thiosulfate ( IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur with the chemical formula . Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid, ...
salt solutions as the acid readily decomposes in water. The decomposition products can include
sulfur
Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
,
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...
,
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...
,
polysulfane
A polysulfane is a chemical compound of formula , where ''n'' > 1 (although disulfane () is sometimes excluded). Compounds containing 2 – 8 sulfur atoms have been isolated, longer chain compounds have been detected, but only in solution.R. Steud ...
s,
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
and
polythionates, depending on the reaction conditions.
[.] Anhydrous methods of producing the acid were developed by Max Schmidt:
:
:
:
The anhydrous acid also decomposes above −5 °C:
:
Structure

The isomer is more stable than the isomer as established by
Hartree–Fock/
ab initio calculations with a 6-311 G**
basis set and MP2 to MP4 refinements.
The theoretically predicted structure conforms with the
double bond rule
In chemistry, the double bond rule states that elements with a principal quantum number (''n'') greater than 2 for their valence electrons ( period 3 elements and higher) tend not to form multiple bonds (e.g. double bonds and triple bonds). Do ...
.
An isomer of thiosulfuric acid is the
adduct
In chemistry, an adduct (; alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is ...
of
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...
and
sulfur trioxide
Sulfur trioxide (alternative spelling sulphur trioxide) is the chemical compound with the formula SO3. It has been described as "unquestionably the most conomicallyimportant sulfur oxide". It is prepared on an industrial scale as a precursor to ...
, , which can also be prepared at low temperature. It is a white crystalline solid.
References
{{Hydrogen compounds
Hydrogen compounds
Sulfur oxoacids
Thiosulfates