A polysulfane is a chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 of formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

x, where x > 1, although sometimes disulfane, H2S2 is excluded. Polysulfanes consist of unbranched chains of sulfur atoms terminated
An end-group in polymer chemistry is a constitutional unit that is an extremity of a macromolecule or oligomer molecule. For example the end-group of a PET polyester may be an alcohol group or a carboxylic acid group...

 with hydrogen. Compounds containing 2-8 concatenated sulfur atoms have been isolated, longer chain compounds have been detected, but only in solution. H2S2 is colourless, higher members are yellow with the colour increasing with the sulfur content. Even a trace of alkali
In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...

 will cause chemical decomposition
Chemical decomposition
Chemical decomposition, analysis or breakdown is the separation of a chemical compound into elements or simpler compounds. It is sometimes defined as the exact opposite of a chemical synthesis. Chemical decomposition is often an undesired chemical reaction...

 and containers need to treated with acid to remove any traces of alkali.

In the chemical literature the term polysulfanes is sometimes used for compounds containing (Sn), e.g. organic polysulfanes R(Sn)R.

Chemistry and properties

Polysulfanes are thermodynamically unstable with respect to decomposition (disproportionation) to H2S and sulfur
H2Sn H2S + (n1)/8 S8

However the production of polysulfide
Polysulfides are a class of chemical compounds containing chains of sulfur atoms. There are two main classes of polysulfides: anions and organic polysulfides. Anions have the general formula Sn2−. These anions are the conjugate bases of the hydrogen polysulfides H2nSn...

 ions from S2 and S is thermodynamically favourable
S2 + (n-1) S Sn2 ; ΔH= ve

Attempting to make a polysulfane by acidifying an alkali metal polysulfide salt (e.g. sodium disulfide) simply produces hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...

, H2S, and sulfur. Polysulfanes can be made from polysulfides by pouring polysulfide into cooled concentrated hydrochloric acid to produce a mixture of metastable polysulfanes as a yellow oil, from which individual compounds may be separated by fractional distillation. Other more selective syntheses are:
Na2Sn + 2HCl 2NaCl + H2Sn (n=4-6)

SnCl2 + 2H2Sm 2HCl + H2Sn+2m

The reaction of polysulfanes with sulfur dichloride
Sulfur dichloride
Sulfur dichloride is the chemical compound with the formula SCl2. This cherry-red liquid is the simplest sulfur chloride and one of the most common. It is used as a precursor to organosulfur compounds.-Chlorination of sulfur:...

 or disulfur dichloride
Disulfur dichloride
Disulfur dichloride is the chemical compound with the formula S2Cl2 . Some alternative names for this compound are sulfur monochloride , disulphur dichloride and sulphur monochloride...

 produces long chain dichloropolysulfanes
2SCl2 + H2Sn 2HCl + S2+nCl2
2S2Cl2 + H2Sn 2HCl +S4+nCl2

The reaction with a sulfite
Sulfites are compounds that contain the sulfite ion SO. The sulfite ion is the conjugate base of bisulfite. Although the acid itself is elusive, its salts are widely used.-Structure:...

 salt (a base) quantitatively decomposes the polysulfane to produce thiosulfate
Thiosulfate is an oxyanion of sulfur. The prefix thio indicates that thiosulfate ion is a sulfate ion with one oxygen replaced by a sulfur. Thiosulfate occurs naturally and is produced by certain biochemical processes...

and hydrogen sulfide
(n1)SO32 + H2Sn (n1)S2O32 + H2S
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