Potassium bisulfate

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Potassium bisulfate
Potassium bisulfate.jpg
Crude potassium bisulfate leftover from nitric acid synthesis
IUPAC name
Potassium hydrogen sulfate
Other names
Potassium acid sulfate
Sal enixum
Molar mass 136.169 g/mol
Appearance White 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 FischerScientific
Lethal dose or concentration (LD, LC):
2340 mg/kg
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).
Infobox references

Potassium bisulfate is an acid salt of potassium, with the formula KHSO4, made from the partial neutralization of a potassium base.



Potassium bisulfate will decompose when heated above 250-300°C to form potassium pyrosulfate and water:

2 KHSO4 → K2S2O7 + H2O

Heating the potassium pyrosulfate above 600°C will give off sulfur trioxide and leave behind potassium sulfate. Strong heating of the potassium bisulfate will above this temperature will achieve the same result:

K2S2O7 → K2SO4 + SO3
2 KHSO4 → K2SO4 + SO3 + H2O


Potassium bisulfate is a white solid, soluble in water. It has a density of 2.245 g/cm3.


Unlike its sodium counterpart, potassium bisulfate does not appear to be available as pH lowering chemical for swimming pools.

Addition of Oxone to water will yield potassium bisulfate and hydrogen peroxide. Potassium sulfate will also be a secondary product.

It can best be purchased from eBay and Amazon.


Potassium hydrogen sulfate can be made by reacting two solutions containing equimolar amounts of potassium hydroxide and sulfuric acid:

KOH + H2SO4 → KHSO4 + H2O

The bisulfate is then recrystallized from the solution.

Potassium bisulfate is a side product in Glauber's nitric acid synthesis. Dissolving the solid waste and recrystallizing it from water will give a relative pure potassium bisulfate.




Contact with potassium bisulfate will irritate the skin, eyes and mucous tissues. Despite being a salt rather than a fully saturated acid, potassium bisulfate solutions have a much lower pH than many acids themselves, and should be treated with care. It may also release sulfuric acid fumes upon storage.


In closed plastic or glass containers.


Can be neutralized with any base.


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