Sodium chromate

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Sodium chromate
Chroman sodný.JPG
IUPAC name
Sodium chromate
Other names
Chromic acid, (Na2CrO4), disodium salt
Chromium disodium oxide
7775-11-3 YesY
EC Number 231-889-5
Jmol interactive 3D Image
PubChem 24488
RTECS number GB2955000
UN number 3288
Molar mass 161.97 g/mol
Appearance yellow crystals
Odor odorless
Density 2.698 g/cm3
Melting point 792 °C (1,458 °F; 1,065 K) (anhydrous)
20 °C (decahydrate)
31.8 g/100 mL (0 °C)
84.5 g/100 mL (25 °C)
126.7 g/100 mL (100 °C)
Solubility slightly soluble in ethanol
Solubility in methanol 0.344 g/100 mL (25 °C)
orthorhombic (hexagonal above 413 °C)
142.1 J/mol K
174.5 J/mol K
−1329 kJ/mol
-1232 kJ/mol
Safety data sheet ICSC 1370
Carc. Cat. 2
Muta. Cat. 2
Repr. Cat. 2
Very toxic (T+)
Harmful (Xn)
Corrosive (C)
Dangerous for the environment (N)
R-phrases R45, R46, R60, R61, R21, R25, R26, R34, R42/43, R48/23, R50/53
S-phrases S53, S45, S60, S61
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity (yellow): no hazard code Special hazard OX: Oxidizer. E.g., potassium perchlorateNFPA 704 four-colored diamond
Flash point Non-flammable
Related compounds
Other anions
Sodium dichromate
Sodium molybdate
Sodium tungstate
Other cations
Potassium chromate
Calcium chromate
Barium chromate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Sodium chromate is the inorganic compound with the formula Na2CrO4. It exists as a yellow hygroscopic solid, which can form tetra-, hexa-, and decahydrates. It is an intermediate in the extraction of chromium from its ores. Sodium chromate, like other hexavalent chromium compounds, is toxic and carcinogenic.[1]

Production and reactivity[edit]

It is obtained on a vast scale by roasting chromium ores in air in the presence of sodium carbonate:

Cr2O3 + 2 Na2CO3 + 3/2 O2 → 2 Na2CrO4 + 2 CO2

This process converts the chromium into a water-extractable form, leaving behind iron oxides. Subsequent to its formation, the chromate salt is converted to sodium dichromate, the precursor to most chromium compounds and materials.[1] The industrial route to chromium(III) oxide involves reduction of sodium chromate with sulfur.

Acid-base behavior[edit]

It converts to sodium dichromate when treated with acids:

2 Na2CrO4 + 2 H+ → + H2O + Na2Cr2O7

Further acidification affords chromium trioxide:

Na2CrO4 + H2SO4 → CrO3 + Na2SO4 + H2O


Aside from its central role in the production of chromium from its ores, sodium chromate is used as a corrosion inhibitor in the petroleum industry.[1] It is also a dyeing auxiliary in the textile industry[1] and a wood preservative.[2] It is a diagnostic pharmaceutical in determining red blood cell volume.[3]

In organic chemistry, sodium chromate is used as an oxidant, converting primary alcohols to carboxylic acids and secondary alcohols to ketones.[4]

See also[edit]


  1. ^ a b c d Gerd Anger, Jost Halstenberg, Klaus Hochgeschwender, Christoph Scherhag, Ulrich Korallus, Herbert Knopf, Peter Schmidt, Manfred Ohlinger (2005), "Chromium Compounds", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a07_067 
  2. ^ "Sodium chromate - Pesticide use statistics for 2005". PAN Pesticides Database. Retrieved 2008-06-20. 
  3. ^ Bracco Diagnostics Inc. "chromitope sodium (Sodium Chromate, Cr 51) injection, solution". DailyMed. Retrieved 2008-06-20. 
  4. ^ Louis F. Fieser4-cholesten-3,6-dione" Org. Synth. 1955, 35, 36. doi:10.15227/orgsyn.035.0036

Further reading[edit]