Potassium pyrosulfate

Potassium pyrosulfate
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Names
	IUPAC name dipotassium (sulfonatooxy)sulfonate
	Other names Potassium pyrosulphate; potassium disulfate
Identifiers
CAS Number	7790-62-7
ChemSpider	56432
Jmol 3D model	Interactive image
PubChem	62681
	InChI InChI=1S/2K.H2O7S2/c;;1-8(2,3)7-9(4,5)6/h;;(H,1,2,3)(H,4,5,6)/q2+1;/p-2 Key: KAQHZJVQFBJKCK-UHFFFAOYSA-L ; InChI=1/2K.H2O7S2/c;;1-8(2,3)7-9(4,5)6/h;;(H,1,2,3)(H,4,5,6)/q2+1;/p-2 Key: KAQHZJVQFBJKCK-NUQVWONBAQ ;
	SMILES [O-]S(=O)(=O)OS(=O)(=O)[O-].[K+].[K+] ;
Properties
Chemical formula	K2O7S2
Molar mass	254.31 g·mol−1
Density	2.28 g/cm3
Melting point	325 °C (617 °F; 598 K)
Solubility in water	soluble
Vapor pressure	{{{value}}}
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references

Potassium pyrosulfate, or potassium disulfate, is an inorganic compound with the chemical formula K₂S₂O₇.

Production

Potassium pyrosulfate is obtained by the thermal decomposition of other salts, most directly from potassium bisulfate:^[1]

2 KHSO₄ → K₂S₂O₇ + H₂O

Temperatures above 600°C further decompose potassium pyrosulfate to potassium sulfate and sulfur trioxide however:^[2]

K₂S₂O₇ → K₂SO₄ + SO₃

Other salts, such as potassium trisulfate,^[3] can also decompose into potassium pyrosulfate.

Potassium pyrosulfate contains the pyrosulfate anion which has a dichromate like structure. The geometry can be visualized as a tetrahedron with two corners sharing the SO₄ anion's configuration and a centrally bridged oxygen atom.^[4] A semi-structural formula for the pyrosulfate anion is O₃SOSO₃²⁻. The oxidation state of sulfur in this compound is +6.

Potassium pyrosulfate is used in analytical chemistry; samples are fused with potassium pyrosulfate, (or a mixture of potassium pyrosulfate and potassium fluoride) to ensure complete dissolution prior to a quantitative analysis.^[5]^[6]

The compound is also used as a catalyst in conjunction with vanadium(V) oxide in the industrial production of sulfur trioxide.^[7]

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