Potassium bisulfate

Potassium bisulfate
IUPAC name
Potassium hydrogen sulfate
Other names
Potassium acid sulfate
7646-93-7 YesY
3D model (Jmol) Interactive image
ChemSpider 56396 N
ECHA InfoCard 100.028.722
EC Number 231-594-1
PubChem 516920
RTECS number TS7200000
UN number 2509
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.
-1163.3 kJ/mol
Safety data sheet External MSDS
Corrosive (C)
R-phrases R34, R36, R37, R38
S-phrases (S1/2), S26, S36/37/39, S45
Lethal dose or concentration (LD, LC):
2340 mg*kg−1
Related compounds
Related compounds
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.

Natural Occurrence

Mercallite, the mineralogical form of potassium bisulfate, occurs very rarely. Misenite is another, more complex, form of potassium bisulfate.


Potassium bisulfate is prepared by neutralizing sulfuric acid with an equal molar amount of a potassium containing base, for example potassium hydroxide:[1]

H2SO4 + KOH → KHSO4 + H2O

Potassium bisulfate is also formed by the union of sulfuric acid with potassium sulfate:[2]

H2SO4 + K2SO4 → 2 KHSO4

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

KNO3 + H2SO4 → KHSO4 + HNO3

Chemical Properties

Thermal decomposition of potassium bisulfate forms potassium pyrosulfate and water:[2]

2 KHSO4 → K2S2O7 + H2O

Temperatures above 600 °C further decompose potassium bisulfate to potassium sulfate and sulfur trioxide:[4]

KHSO4 → K2SO4 + SO3 + H2O

Aqueous solutions of potassium bisulfate behave as two separate, uncombined compounds, K2SO4 and H2SO4. Adding ethanol to the solution precipitates out potassium sulfate.


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

See also


  1. McPherson, William (1913). A Course in General Chemistry. New York: Ginn and Company. p. 156. Retrieved 31 December 2015.
  2. 1 2 Washington Wiley, Harvey (1895). Principles and Practice of Agricultural Analysis: Fertilizers. Easton, PA.: Chemical Publishing Co. p. 218. Retrieved 31 December 2015.
  3. Pradyot, Patnaik (2003). Handbook of Inorganic Chemicals. New York: McGraw-Hill. p. 636. ISBN 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.
  5. Brauer, Georg (1963). Handbook of Preparative Inorganic Chemistry Vol. 1, 2nd Ed. Newyork: Academic Press. p. 392. ISBN 978-0121266011.

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