Potassium bisulfate

Potassium bisulfate (potassium bisulphate) 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.

Potassium bisulfate

One potassium cation and one hydrogensulfate anion
Ball-and-stick model of the component ions
Potassium bisulfate crystals on filter paper
Names
IUPAC name Potassium hydrogen sulfate
Other names Potassium acid sulfate
Identifiers
CAS Number	7646-93-7 Y
3D model (JSmol)	Interactive image
ChemSpider	56396 Y
ECHA InfoCard	100.028.722
EC Number	231-594-1
E number	E515(ii) (acidity regulators, ...)
PubChem CID	516920
RTECS number	TS7200000
UNII	1J1K03241F Y
UN number	2509
CompTox Dashboard (EPA)	DTXSID8047715
InChI InChI=1S/K.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+1;/p-1 N Key: CHKVPAROMQMJNQ-UHFFFAOYSA-M N InChI=1/K.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+1;/p-1 Key: CHKVPAROMQMJNQ-REWHXWOFAH
SMILES OS(=O)(=O)[O-].[K+]
Properties
Chemical formula	KHSO4
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 to form potassium pyrosulfate and water)
Solubility in water	36.6 g/100 mL (0 °C) 49 g/100 mL (20 °C) 121.6 g/100 mL (100 °C)
Solubility	soluble in acetone, insoluble in ethanol.
Magnetic susceptibility (χ)	−49.8·10−6 cm3/mol
Thermochemistry
Std enthalpy of formation (ΔfH⦵298)	−1163.3 kJ/mol
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314, H335
Precautionary statements	P260, P261, P264, P271, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P363, P403+P233, P405, P501
Lethal dose or concentration (LD, LC):
LD50 (median dose)	2340 mg*kg−1
Safety data sheet (SDS)	External MSDS
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). N verify (what is YN ?) Infobox references

Preparation

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

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

Uses

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]

Occurrence

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.