Potassium pyrosulfate

Potassium pyrosulfate
Names
	IUPAC name dipotassium (sulfonatooxy)sulfonate
	Other names Potassium pyrosulphate; potassium disulfate
Identifiers
CAS Number	7790-62-7 ;
3D model (JSmol)	Interactive image;
ChemSpider	56432 ;
ECHA InfoCard	100.029.288
EC Number	232-216-8;
PubChem CID	62681;
UNII	AVJ6ZST7L6;
CompTox Dashboard (EPA)	DTXSID10889580 ;
	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	25.4 g/100 mL (20 °C)
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314, H331
Precautionary statements	P260, P261, P264, P271, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P311, P321, P363, P403+P233, P405, P501
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) 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 present in a catalyst in conjunction with vanadium(V) oxide in the industrial production of sulfur trioxide.^[7]

^ Washington Wiley, Harvey (1895). Principles and Practice of Agricultural Analysis: Fertilizers. Easton, PA.: Chemical Publishing Co. p. 218. Retrieved 31 December 2015. Potassium disulfate.
^ Iredelle Dillard Hinds, John (1908). Inorganic Chemistry: With the Elements of Physical and Theoretical Chemistry. New York: John Wiley & Sons. p. 547. Retrieved 31 December 2015. Potassium disulfate.
^ Brauer, Georg (1963). Handbook of Preparative Inorganic Chemistry Vol. 2, 2nd Ed. New York: Academic Press. p. 1716. ISBN 9780323161299.
^ Ståhl, K.; Balic-Zunic, T.; da Silva, F.; Eriksen, K. M.; Berg, R. W.; Fehrmann, R. (2005). "The crystal structure determination and refinements of K₂S₂O₇, KNaS₂O₇ and Na₂S₂O₇ from X-ray powder and single crystal diffraction data". Journal of Solid State Chemistry. 178 (5): 1697–1704. Bibcode:2005JSSCh.178.1697S. doi:10.1016/j.jssc.2005.03.022.
^ Trostbl, L. J.; Wynne, D. J. (1940). "Determination of quartz (free silica) in refractory clays". Journal of the American Ceramic Society. 23 (1): 18–22. doi:10.1111/j.1151-2916.1940.tb14187.x.
^ Sill, C. W. (1980). "Determination of gross alpha, plutonium, neptunium, and/or uranium by gross alpha counting on barium sulphate". Analytical Chemistry. 52 (9): 1452–1459. doi:10.1021/ac50059a018.
^ Burkhardt, Donald (1965). "Sulfur trioxide production, US3362786A". Google Patents. Retrieved 31 December 2015.