Potassium bisulfate

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Potassium bisulfate
One potassium cation and one hydrogensulfate anion
Ball-and-stick model of the component ions
Potassium bisulfate crystals on filter paper
IUPAC name
Potassium hydrogen sulfate
Other names
Potassium acid sulfate
  • 7646-93-7 checkY
3D model (JSmol)
ECHA InfoCard 100.028.722 Edit this at Wikidata
EC Number
  • 231-594-1
E number E515(ii) (acidity regulators, ...)
RTECS number
  • TS7200000
UN number 2509
  • InChI=1S/K.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+1;/p-1 ☒N
  • InChI=1/K.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+1;/p-1
  • OS(=O)(=O)[O-].[K+]
Molar mass 136.169 g/mol
Appearance colorless solid
Odor odorless
Density 2.245 g/cm3
Melting point 197 °C (387 °F; 470 K)
Boiling point 300 °C (572 °F; 573 K) (decomposes)
36.6 g/100 mL (0 °C)
49 g/100 mL (20 °C)
121.6 g/100 mL (100 °C)
Solubility soluble in acetone, ethanol.
−49.8·10−6 cm3/mol
-1163.3 kJ/mol
Safety data sheet External MSDS
Corrosive (C)
R-phrases (outdated) R34, R36, R37, R38
S-phrases (outdated) (S1/2), S26, S36/37/39, S45
Lethal dose or concentration (LD, LC):
2340 mg*kg−1
Related compounds
Related compounds
Potassium sulfate
Sodium bisulfate
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 bisulfate is an inorganic compound with the chemical formula KHSO4 and is the potassium acid salt of sulfuric acid. It is a white, water-soluble solid.


More than 1 million tons were produced in 1985 as the initial stage in the Mannheim process for producing potassium sulfate. The relevant conversion is the exothermic reaction of potassium chloride and sulfuric acid:[1][2]

KCl + H2SO4 → HCl + KHSO4

Potassium bisulfate is a by-product in the production of nitric acid from potassium nitrate and sulfuric acid:[3]

KNO3 + H2SO4 → KHSO4 + HNO3

Chemical Properties[edit]

Thermal decomposition of potassium bisulfate forms potassium pyrosulfate:[1]

2 KHSO4 → K2S2O7 + H2O

Above 600 °C potassium pyrosulfate converts to potassium sulfate and sulfur trioxide:[4]

K2S2O7 → K2SO4 + SO3


Potassium bisulfate is commonly used to prepare potassium bitartrate for winemaking.[5] Potassium bisulfate is also used as a disintegrating agent in analytical chemistry or as a precursor to prepare potassium persulfate, a powerful oxidizing agent.[6]


Mercallite, the mineralogical form of potassium bisulfate, occurs very rarely.[7] Misenite is another more complex form of potassium bisulfate with the formula K8H6(SO4)7.


  1. ^ a b Washington Wiley, Harvey (1895). Principles and Practice of Agricultural Analysis: Fertilizers. Easton, PA.: Chemical Publishing Co. p. 218. Retrieved 31 December 2015. Potassium disulfate.
  2. ^ H. Schultz, G. Bauer, E. Schachl, F. Hagedorn, P. Schmittinger (2005). "Potassium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a22_039. ISBN 978-3527306732.CS1 maint: uses authors parameter (link)
  3. ^ Pradyot, Patnaik (2003). Handbook of Inorganic Chemicals. New York: McGraw-Hill. p. 636. ISBN 978-0070494398.
  4. ^ 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.
  5. ^ Weisblatt, Jayne; Montney, Charles B. (2006). Chemical Compounds. ISBN 978-1-4144-0453-0.
  6. ^ Brauer, Georg (1963). Handbook of Preparative Inorganic Chemistry Vol. 1, 2nd Ed. New York: Academic Press. p. 392. ISBN 978-0121266011.
  7. ^ "Mercallite: Mineral information, data and localities". mindat.org. Retrieved 2019-05-08.