Potassium Chromate - Wikipedia

Not to be confused with Potassium dichromate. Potassium chromate

Names
IUPAC name Potassium chromate
Other names Potassium dichromate, Chromic acid, (K2CrO4), dipotassium salt
Identifiers
CAS Number	7789-00-6 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:75249 N
ChemSpider	22999 N
ECHA InfoCard	100.029.218
EC Number	232-140-5
PubChem CID	24597
RTECS number	GB2940000
UNII	5P0R38CN2X Y
UN number	3077
CompTox Dashboard (EPA)	DTXSID8064858
InChI InChI=1S/Cr.2K.4O/q;2*+1;;;2*-1 NKey: XMXNVYPJWBTAHN-UHFFFAOYSA-N N InChI=K2CrO4Key: XMXNVYPJWBTAHN-QALQIXLOAU
SMILES [O-][Cr](=O)(=O)[O-].[K+].[K+]
Properties
Chemical formula	K2CrO4
Molar mass	194.189 g·mol−1
Appearance	Yellow powder
Odor	odorless
Density	2.7320 g/cm3
Melting point	968 °C (1,774 °F; 1,241 K)
Boiling point	1,000 °C (1,830 °F; 1,270 K)
Solubility in water	63.7 g/100 mL (20 °C (68 °F; 293 K)) 75.1 g/100 mL (80 °C (176 °F; 353 K)) 79.2 g/100 mL (100 °C (212 °F; 373 K))
Magnetic susceptibility (χ)	3.9×10−6 cm3/mol
Refractive index (nD)	1.74
Structure
Crystal structure	rhombic
Hazards
GHS labelling:[2]
Pictograms
Signal word	Danger
Hazard statements	H315, H317, H319, H335, H340, H350, H410
Precautionary statements	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)	[1] 2 0 0
Safety data sheet (SDS)	Fisher Scientific[1]
Related compounds
Other anions	Potassium dichromate
Other cations	Sodium chromate Calcium chromate Barium chromate
Related chromates	Potassium hypochromate Potassium perchromate
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

Chemical compound

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.

Production and reactions

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It is prepared by treating potassium dichromate with potassium hydroxide:[3]

K2Cr2O7(aq) + 2 KOH → 2 K2CrO4 + H2O

Or, the fusion of potassium hydroxide and chromium trioxide:

2 KOH + CrO3 → K2CrO4 + H2O

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

Applications

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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.[4]

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 and sodium chloride (they can be used as standard as well as titrant for each other) as potassium chromate turns red in the presence of excess of silver ions.[5]

Structure

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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).[4] These structures are complex, although the chromate ion adopts the typical tetrahedral geometry.[6][better source needed]

• Structure of β-K2CrO4
• Coordination sphere of one of two types of K+ site
• The environment about the tetrahedral CrO2−4 center in β-K2CrO4

Safety

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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 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.[7]

As a highly soluble hexavalent chromium compound, potassium chromate is also acutely toxic, though it is poorly absorbed from the intestinal tract.[7] The compound is also corrosive and exposure may produce severe eye damage or blindness.[1]

References

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1. ^ a b c "SDS - Potassium Chromate". fishersci.com. Thermo Fisher Scientific. 29 March 2024. Retrieved 31 October 2025.
2. ^ Sigma-Aldrich Co., Potassium chromate.
3. ^ PubChem. "Potassium Chromate". pubchem.ncbi.nlm.nih.gov. Retrieved 2025-12-08.
4. ^ a b 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.
5. ^ "Titration | Definition, Types, & Facts | Britannica". Encyclopedia Britannica. Archived from the original on 2025-09-07. Retrieved 2025-12-08.
6. ^ Gaultier, M.; Pannetier, G. "Structure cristalline de la forme 'basse temperature' du sulfate de potassium K2SO4-beta" (Crystal structure of the "low temperature" β-form of potassium sulfate) Bulletin de la Société Chimique de France 1968, vol. 1, pp. 105-12.
7. ^ a b 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.

v t e Potassium compounds
H, (pseudo)halogens	KBr KBrO3 KBrO4 KCl KClO KClO2 KClO3 KClO4 KCN KCNO KF KHF2 KH KI KIO3 KIO4 KOCN KSCN
chalcogens	K2O KOH K2O2 KO2 KO3 K2S KHS K2SO3 KHSO3 K2SO4 KHSO4 KHSO5 K2S2O3 K2S2O5 K2S2O7 K2S2O8 K2Se K2SeO4 K2Te K2TeO3 K2Po
pnictogens	KAsO2 KH2AsO4 K3N KN3 KNH2 KNO2 KNO3 K2HPO4 KH2PO3 KH2PO4 K3P KPF6 K3PO4
B, C group	KBF4 K2Al2B2O7 K2Al2O4 K2CO3 KHCO3 K2SiF6 K2SiO3
transition metals	K2ReBr6 KCrO3Cl K4Mo2Cl8 K2OsCl6 K2PtCl4 K2PtCl6 K2ReCl6 K3CrO4 K2CrO4 K3CrO8 K2Cr2O7 K2FeO4 K4[Fe(CN)6]·3H2O K3[Fe(CN)6] K3[Fe(C2O4)3] K2TiF6 K2ReF6 KAsF6 K2ZrF6 K2ReI6 K2[Pt(CN)4] K2MnO4 KMnO4
organic	KHCO2 KCH3CO2 KCF3CO2 KHC2O4 C6H5COOK KC8H5O4 KC12H23O2 KC18H35O2 CF3KO3S

v t e Chromates and dichromates
Chromates	Na2CrO4 K2CrO4 Cs2CrO4 BeCrO4 MgCrO4 CaCrO4 SrCrO4 BaCrO4 Fe2(CrO4)3 NiCrO4 Ag2CrO4 ZnCrO4 CdCrO4 PbCrO4 Pb2CrO5 [NH4]2CrO4 Chlorochromates KCrO3Cl [C5H5NH]CrO3Cl Chromate esters CrO2(OC(CH3)3)2 CrO2(OSi(OCH3)3)2
Dichromates	Na2Cr2O7 K2Cr2O7 Ag2Cr2O7 [NH4]2Cr2O7 [C5H5NH]2Cr2O7
Other chromates	EuCrO4 CrO5
Related	H2CrO4/H2Cr2O7 CrO3