Potassium chromate

Potassium chromate
Names
IUPAC name
Potassium chromate
Other names
  • Chromic acid, dipotassium salt
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.029.218 Edit this at Wikidata
EC Number
  • 232-140-5
RTECS number
  • GB2940000
UNII
UN number 3077
  • InChI=1S/Cr.2K.4O/q;2*+1;;;2*-1 X markN
    Key: XMXNVYPJWBTAHN-UHFFFAOYSA-N X markN
  • InChI=K2CrO4
    Key: XMXNVYPJWBTAHN-QALQIXLOAU
  • [O-][Cr](=O)(=O)[O-].[K+].[K+]
Properties
K2CrO4
Molar mass 194.189 g·mol−1
Appearance Yellow orthorhombic crystals
Odor odorless
Density 2.73 g/cm3
Melting point 975 °C (1,787 °F; 1,248 K)
65.0 g/100 mL
−3.9×10−6 cm3/mol
1.74
Structure
  • hexagonal (α-form, above 666 °C (1,231 °F; 939 K))
  • rhombic (β-form, common)
Hazards
GHS labelling:
GHS07: Exclamation markGHS08: Health hazardGHS09: Environmental hazard
Danger
H315, H317, H319, H335, H340, H350, H410
P201, P202, P261, P264, P271, P272, P273, P280, P302+P352, P304+P340+P312, P305+P351+P338, P308+P313, P333+P313, P337+P313, P362, P391, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
0
0
Safety data sheet (SDS) Fisher Scientific
Related compounds
Other anions
 Potassium dichromate
Other cations
Related chromates
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Potassium chromate is the inorganic compound with the formula K2CrO4. This yellow solid is the potassium salt of the chromate anion. It is a common laboratory chemical, whereas sodium chromate is important industrially.

Structure

Two crystalline forms are known, both being very similar to the corresponding potassium sulfate. Orthorhombic β-K2CrO4 is the common form, but it converts to an α-form above 666 °C (1,231 °F).

Production and reactions

It is prepared by treating potassium dichromate with potassium hydroxide:[citation needed]

K2Cr2O7(aq) + 2 KOH → 2 K2CrO4 + H2O

Or with potassium carbonate:

K2Cr2O7 + K2CO3 → 2 K2CrO4 + CO2

Or, the fusion of potassium hydroxide and chromium trioxide:[citation needed]

2 KOH + CrO3 → K2CrO4 + H2O

When treated with lead(II) nitrate, it gives an orange-yellow precipitate, lead(II) chromate.[citation needed]

Applications

Unlike the less expensive sodium salt, the potassium salt is mainly used for laboratory work in situations where an anhydrous salt is required, or as an oxidizing agent in organic synthesis.

It is used in qualitative inorganic analysis, e.g. as a colorimetric test for silver ion. It is also used as an indicator in precipitation titrations with silver nitrate to measure levels of chloride ion (the Mohr method of determining chloride) since red silver chromate is precipitated in the presence of any excess of silver ions when potassium chromate is present. This titration proceeds by the following reactions, where silver nitrate is used as the titrant:

Ag+ + Cl− → AgCl
2 Ag+ + CrO−4 → Ag2CrO4

Safety

As with other Cr(VI) compounds, potassium chromate is carcinogenic. Positive associations with lung cancer at a very high rate, and nasal / sinus cancer at a 100x lower rate than lung cancer have been found using worker exposure data. In general, less soluble chromates are a larger chronic hazard as they can be encapsulated in the lung without being absorbed and excreted, giving more time for reactive intermediates to be produced. Animal data indicates a potential for impaired fertility, heritable genetic damage and harm to unborn children, along with other types of cancer via less common exposure routes.

As a highly soluble hexavalent chromium compound, potassium chromate is also acutely toxic, though it is poorly absorbed from the intestinal tract. The compound is also corrosive and exposure may produce severe eye damage or blindness.

References

  1. ↑ Lide, David R., ed. (2004). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. pp. 4–76, 4–147. ISBN 978-0-8493-0485-9.
  2. ↑ "Potassium Chromate". Pubchem.ncbi.nlm.nih.gov. Retrieved August 8, 2026.
  3. ↑ Sigma-Aldrich Co., Potassium chromate. Retrieved on 31 October 2025.
  4. 1 2 3 "SDS - Potassium Chromate". fishersci.com. Thermo Fisher Scientific. 29 March 2024. Retrieved 31 October 2025.
  5. 1 2 Anger, Gerd; Halstenberg, Jost; Hochgeschwender, Klaus; Ulrich Korallus, Christoph Scherhag; Knopf, Herbert; Schmidt, Peter; Ohlinger, Manfred. "Chromium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a07_067. ISBN 978-3-527-30673-2.
  6. ↑ Fedoroff, Basil T.; Sheffield, Oliver E. (1 January 1966). "C - Chromates - Potassium Chromate". Encyclopedia of Explosives and Related Items (PDF) (Technical report). Vol. 3, Chlorides through Detonating Relays. Picatinny Arsenal, NJ: U.S. Army Armament Research Development And Engineering Center - TACOM, ARDEC - Warheads, Energetics And Combat Support Armaments Center. pp. C281-2. AD0653029, PATR 2700.
  7. ↑ Chloride, titrimetric, Mohr (Report). National Environment Methods Index (NEMI). I-1183-85.
  8. 1 2 Volume 100C: Arsenic, Metals, Fibres, and Dusts (PDF). Lyon, France: World Health Organization - International Agency for Research on Cancer. 2012 [17–24 March 2009]. pp. 153–64. ISBN 978-92-832-0135-9. Retrieved 2020-01-05.