Sodium chromate

Last updated
Sodium chromate
Sodium-chromate.svg
Chroman sodny.JPG
Names
IUPAC name
Sodium chromate
Other names
Chromic acid, (Na2CrO4), disodium salt
Chromium disodium oxide
Rachromate
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.028.990 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 231-889-5
PubChem CID
RTECS number
  • GB2955000
UNII
UN number 3288
  • InChI=1S/Cr.2Na.4O/q;2*+1;;;2*-1
  • [O-][Cr](=O)(=O)[O-].[Na+].[Na+]
Properties
Na2CrO4
Molar mass 161.97 g/mol
Appearanceyellow 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)
+55.0·10−6 cm3/mol
Structure
orthorhombic (hexagonal above 413 °C)
Thermochemistry
142.1 J/mol K
Std molar
entropy
(S298)
174.5 J/mol K
−1329 kJ/mol
-1232 kJ/mol
Hazards
GHS labelling:
GHS-pictogram-acid.svg GHS-pictogram-skull.svg GHS-pictogram-exclam.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
Danger
H301, H312, H314, H317, H330, H334, H340, H350, H360, H372, H410
P201, P202, P260, P261, P264, P270, P271, P272, P273, P280, P281, P284, P285, P301+P310, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P304+P341, P305+P351+P338, P308+P313, P310, P312, P314, P320, P321, P322, P330, P333+P313, P342+P311, P363, P391, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability (yellow): no hazard codeSpecial hazard OX: Oxidizer. E.g. potassium perchlorate
3
0
OX
Flash point Non-flammable
Safety data sheet (SDS) ICSC 1370
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).
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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.

Contents

Production and reactivity

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

2Cr2O3 + 4 Na2CO3 + 3 O2 → 4 Na2CrO4 + 4 CO2

This process converts the chromium into a water-extractable form, leaving behind iron oxides. Typically calcium carbonate is included in the mixture to improve oxygen access and to keep silicon and aluminium impurities in an insoluble form. The process temperature is typically around 1100 °C. [1] For lab and small scale preparations a mixture of chromite ore, sodium hydroxide and sodium nitrate reacting at lower temperatures may be used (even 350 C in the corresponding potassium chromate system). [2] Subsequent to its formation, the chromate salt is converted to sodium dichromate, the precursor to most chromium compounds and materials. [3] The industrial route to chromium(III) oxide involves reduction of sodium chromate with sulfur.

Acid-base behavior

It converts to sodium dichromate when treated with acids:

2 Na2CrO4 + 2HCl → Na2Cr2O7 + 2NaCl + H2O

Further acidification affords chromium trioxide:

Na2CrO4 + H2SO4 → CrO3 + Na2SO4 + H2O

Uses

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. [3] It is also a dyeing auxiliary in the textile industry. [3] It is a diagnostic pharmaceutical in determining red blood cell volume. [4]

In organic chemistry, sodium chromate is used as an oxidant, converting primary alcohols to carboxylic acids and secondary alcohols to ketones. [5] Sodium chromate is a strong oxidizer.

Safety

As with other Cr(VI) compounds, sodium chromate is carcinogenic. [6] The compound is also corrosive and exposure may produce severe eye damage or blindness. [7] Human exposure further encompasses impaired fertility, heritable genetic damage and harm to unborn children.

See also

Related Research Articles

<span class="mw-page-title-main">Chromium</span> Chemical element, symbol Cr and atomic number 24

Chromium is a chemical element; it has symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal.

Chromic acid is jargon for a solution formed by the addition of sulfuric acid to aqueous solutions of dichromate. It consists at least in part of chromium trioxide.

<span class="mw-page-title-main">Chromate and dichromate</span> Chromium(VI) anions

Chromate salts contain the chromate anion, CrO2−
4
. Dichromate salts contain the dichromate anion, Cr
2
O2−
7
. They are oxyanions of chromium in the +6 oxidation state and are moderately strong oxidizing agents. In an aqueous solution, chromate and dichromate ions can be interconvertible.

<span class="mw-page-title-main">Potassium dichromate</span> Chemical compound

Potassium dichromate, K2Cr2O7, is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications. As with all hexavalent chromium compounds, it is acutely and chronically harmful to health. It is a crystalline ionic solid with a very bright, red-orange color. The salt is popular in laboratories because it is not deliquescent, in contrast to the more industrially relevant salt sodium dichromate.

<span class="mw-page-title-main">Pyridinium chlorochromate</span> Chemical compound

Pyridinium chlorochromate (PCC) is a yellow-orange salt with the formula [C5H5NH]+[CrO3Cl]. It is a reagent in organic synthesis used primarily for oxidation of alcohols to form carbonyls. A variety of related compounds are known with similar reactivity. PCC offers the advantage of the selective oxidation of alcohols to aldehydes or ketones, whereas many other reagents are less selective.

<span class="mw-page-title-main">Chromium trioxide</span> Chemical compound

Chromium trioxide is an inorganic compound with the formula CrO3. It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name. This compound is a dark-purple solid under anhydrous conditions and bright orange when wet. The substance dissolves in water accompanied by hydrolysis. Millions of kilograms are produced annually, mainly for electroplating. Chromium trioxide is a powerful oxidiser, a mutagen, and a carcinogen.

<span class="mw-page-title-main">Copper chromite</span> Chemical compound

Copper chromite is an inorganic compound with the formula Cu2Cr2O5. It is a black solid that is used to catalyze reactions in organic synthesis.

<span class="mw-page-title-main">Potassium chromate</span> 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.

<span class="mw-page-title-main">Sodium dichromate</span> Inorganic compound

Sodium dichromate is the inorganic compound with the formula Na2Cr2O7. However, the salt is usually handled as its dihydrate Na2Cr2O7·2H2O. Virtually all chromium ore is processed via conversion to sodium dichromate and virtually all compounds and materials based on chromium are prepared from this salt. In terms of reactivity and appearance, sodium dichromate and potassium dichromate are very similar. The sodium salt is, however, around twenty times more soluble in water than the potassium salt (49 g/L at 0 °C) and its equivalent weight is also lower, which is often desirable.

<span class="mw-page-title-main">Chromyl chloride</span> Chemical compound

Chromyl chloride is an inorganic compound with the formula CrO2Cl2. It is a reddish brown compound that is a volatile liquid at room temperature, which is unusual for transition metal compounds.

<span class="mw-page-title-main">Caesium chromate</span> Chemical compound

Caesium chromate or cesium chromate is an inorganic compound with the formula Cs2CrO4. It is a yellow crystalline solid that is the caesium salt of chromic acid, and it crystallises in the orthorhombic system.

<span class="mw-page-title-main">Chromium compounds</span> Chemical compounds containing chromium

Chromium compounds are compounds containing the element chromium (Cr). Chromium is a member of group 6 of the transition metals. The +3 and +6 states occur most commonly within chromium compounds, followed by +2; charges of +1, +4 and +5 for chromium are rare, but do nevertheless occasionally exist.

<span class="mw-page-title-main">Potassium chlorochromate</span> Chemical compound

Potassium chlorochromate is an inorganic compound with the formula KCrO3Cl. It is the potassium salt of chlorochromate, [CrO3Cl]. It is a water-soluble orange compound is used occasionally for oxidation of organic compounds. It is sometimes called Péligot's salt, in recognition of its discoverer Eugène-Melchior Péligot.

<span class="mw-page-title-main">Nickel(II) chromate</span> Chemical compound

Nickel(II) chromate (NiCrO4) is an acid-soluble compound, red-brown in color, with high tolerances for heat. It and the ions that compose it have been linked to tumor formation and gene mutation, particularly to wildlife.

<span class="mw-page-title-main">Calcium chromate</span> Chemical compound

Calcium chromate is an inorganic compound with the formula CaCrO4, i.e. the chromate salt of calcium. It is a bright yellow solid which is normally found in the dihydrate form CaCrO4·2H2O. A very rare anhydrous mineral form exists in nature, which is known as chromatite.

Alcohol oxidation is a collection of oxidation reactions in organic chemistry that convert alcohols to aldehydes, ketones, carboxylic acids, and esters where the carbon carries a higher oxidation state. The reaction mainly applies to primary and secondary alcohols. Secondary alcohols form ketones, while primary alcohols form aldehydes or carboxylic acids.

<span class="mw-page-title-main">Chromium(VI) oxide peroxide</span> Chemical compound

Chromium(VI) oxide peroxide is the name given to a collection of chromium coordination complexes. They have the formula CrO(O2)2L where L is a ligand. These species are dark blue and often labile. They all feature oxo ligand and two peroxo ligands, with the remaining coordination sites occupied by water, hydroxide, ether, or other Lewis bases.

<span class="mw-page-title-main">Jones oxidation</span> Oxidation of alcohol

The Jones oxidation is an organic reaction for the oxidation of primary and secondary alcohols to carboxylic acids and ketones, respectively. It is named after its discoverer, Sir Ewart Jones. The reaction was an early method for the oxidation of alcohols. Its use has subsided because milder, more selective reagents have been developed, e.g. Collins reagent.

<span class="mw-page-title-main">Potassium hypochromate</span> Chemical compound

Potassium hypochromate is a chemical compound with the formula K3CrO4 with the unusual Cr5+ ion. This compound is unstable in water but stable in alkaline solution and was found to have a similar crystal structure to potassium hypomanganate.

Europium(III) chromate is a chemical compound composed of europium, chromium and oxygen with europium in the +3 oxidation state, chromium in the +5 oxidation state and oxygen in the −2 oxidation state. It has the chemical formula of EuCrO4.

References

  1. IARC Monographs 49 Ch. 2 (PDF). ISBN   9789283212492.
  2. Zhi Sun, Yi Zhang, Shi-Li Zheng, Yang Zhang (2009). "A new method of potassium chromate production from chromite and KOH-KNO3-H2O binary submolten salt system". AIChE Journal. 55 (10): 2646–2656. doi:10.1002/aic.11871.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. 1 2 3 Gerd Anger, Jost Halstenberg, Klaus Hochgeschwender, Christoph Scherhag, Ulrich Korallus, Herbert Knopf, Peter Schmidt, Manfred Ohlinger. "Chromium Compounds". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a07_067. ISBN   978-3527306732.{{cite encyclopedia}}: CS1 maint: multiple names: authors list (link)
  4. Bracco Diagnostics Inc. "chromitope sodium (Sodium Chromate, Cr 51) injection, solution". DailyMed. Retrieved 2008-06-20.
  5. Louis F. Fieser4-cholesten-3,6-dione" Org. Synth. 1955, 35, 36. doi : 10.15227/orgsyn.035.0036
  6. IARC (2012) [17-24 March 2009]. Volume 100C: Arsenic, Metals, Fibres, and Dusts (PDF). Lyon: International Agency for Research on Cancer. ISBN   978-92-832-0135-9. Archived from the original (PDF) on 2020-03-17. Retrieved 2020-01-05. There is sufficient evidence in humans for the carcinogenicity of chromium (VI) compounds. Chromium (VI) compounds cause cancer of the lung. Also positive associations have been observed between exposure to Chromium (VI) compounds and cancer of the nose and nasal sinuses. There is sufficient evidence in experimental animals for the carcinogenicity of chromium (VI) compounds. Chromium (VI) compounds are carcinogenic to humans (Group 1).
  7. "Potassium dichromate MSDS". JT Baker.

Further reading