SODIUM DICHROMATE
SODIUM DICHROMATE
CAS number: 10588-01-9
EC Number: 234-190-3
Chemical formula: Na2Cr2O7
Molar mass: 261.97 g/mol
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.
Sodium Dichromate is a strong oxidising agent and a source in preparing chromium based derivatives.
Sodium dichromate is used in metal passivation and finds applications across diverse industries including pigments and coatings, screen printing in photographic engraving, electroplating, pyrotechnics and explosives.
As a wood preservative, Sodium Dichromate protects wood from termites and fungi while in metal treatment it works as a corrosion inhibitor.
Sodium dichromate is also used in pigment preparations like chrome oxide green and lead chromate.
APPLICATIONS of Sodium dichromate:
-Source in preparing chromium based derivative
-Screen printing & Photographic engraving
-Electroplating
-Pyrotechnics and explosives
-Pigment preparation like chrome oxide green, lead chromate etc.
-Wood preservative for protection from termites and fungi
-Metal treating and corrosion inhibitor
-Oil well drilling as treating agents in drilling mud systems
-Catalyst for the chromium metal production
-As an oxidizing agent in organic synthesis
Sodium dichromate or Na2Cr2O7 is an orange to red-coloured, crystalline, and inorganic compound which emits toxic chromium fumes on heating.
Sodium dichromate is highly corrosive in nature and is a strong oxidizing agent.
This substance is usually used to produce other chromium compounds but is also used for drilling muds, metal treatments, wood preservatives, production of dyes and organic chemicals, and as a corrosion inhibitor.
In this article, we will learn about sodium dichromate in detail like the sodium dichromate reaction, sodium dichromate chemical formula, its uses, properties, density, and structure.
Let us first learn about what is sodium dichromate or Na2Cr2O7 .
What is Sodium Dichromate?
Sodium dichromate or Na2Cr2O7 is an inorganic compound.
Sodium dichromate is also known as bichromate of soda, disodium dichromate, or sodium dichromate (VI).
Sodium dichromate is known to be a powerful oxidizing agent and is highly corrosive.
Sodium dichromate is a red to reddish-orange crystalline solid.
Sodium dichromate is odourless and dissolves in water, methanol and ethanol.
Sodium dichromate is commonly used as a corrosion inhibitor.
On heating, Sodium dichromate liberates chromium fumes that are toxic in nature.
Sodium Dichromate Structure
Sodium dichromate structure is shown below:
Production of Sodium Dichromate
On a larger scale, sodium dichromate is obtained from ores which contain chromium (III) oxides.
Let us have a look at the Na2Cr2O7 reaction and how it is produced.
The first step is to fuse the ore with a base such as sodium carbonate.
Next, maintain a temperature around 1000 °C.
Then, conduct the above two steps in the presence of air that is the source of oxygen.
The reaction is given below:
2Cr2O3 + 4Na2CO3 + 3O2 —> 4Na2CrO4 + 4CO2
These steps solubilize chromium and allow it to extract in the hot water.
The other components present in the ore are poorly soluble and therefore, acidification of the resulting aqueous extract by utilizing carbon dioxide or sulfuric acid helps to produce dichromate.
The reaction is as follows:
2Na2CrO4 + 4CO + H2O —> Na2CrO7 + 2NaHCO3
2Na2CrO4 + H2SO4 —> Na2CrO7 + Na2So4 + H2O
Using the process of crystallization, dichromate is extracted as a dihydrate.
Sodium Dichromate Uses
Apart from its importance for the production of other chromium products, sodium dichromate also has many uses as an ingredient in the production of the following materials:
Metallic Finish – it helps to prevent corrosion, making it easier to clean the metallic surfaces and allows the paint to stick.
Organic products – used as oxidisers for the production of vitamin K and wax.
Pigments – used in making inorganic chromate pigments where it produces a range of light-stable colours.
Some grades of chromate are used for the prevention of corrosion in undercoats and primers.
Ceramics – used to produce coloured glass and ceramic glaze.
Textiles – used as a mordant in the acidic dyes to improve colour-fast properties.
Sodium dichromate is used in the chromium sulphate production.
Application areas of Sodium dichromate:
Sodium dichromate has various uses, the most important direct uses are:
-Metal finishing/surface treatment: corrosion resistance, paint adhesion properties, supports cleaning the metal surface
-Metal working auxiliary
-Electroplating
-Pigments: preparation of pigments and as corrosion inhibitor
-ceramics: used in the production of colored glass and ceramic glazes
-Catalyst for the chromium metal production
-Laboratory chemical
-Initial product for chemical reactions
-Chemical intermediate
-Surface modifiers
-Surface additive
-Chromium source in preparing other chromium compounds (see chrome based chemicals)
-Formulation (mixing) of preparations and/or re-packaging (excluding alloys)
-Manufacture of plastics products, including compounding and conversion
-Industrial uses: uses of substances as such or in preparations at industrial sites
Sodium Dichromate is a bright orange inorganic chromium salt that is very similar to potassium dichromate in its appearance.
Sodium dichromates chemical formula is Na2Cr2O7, but is used in its dihydrate form Na2Cr2O7.2H2O.
Sodium dichromate is around 20 times more water-soluble than potassium dichromate, it also has a relatively low equivalent weight.
The production of almost all chromium ores and chromate based compounds is through this salt.
Na2Cr2O7: Sodium dichromate
Molecular weight of Na2Cr2O7: 261.97 g/mol (anhydrous)
Density of Sodium dichromate: 2.52 g/dm3
Melting point of Sodium dichromate: 356.7 °C
Boiling point of Sodium dichromate: 400 °C
Chemical Properties of Sodium dichromate:
Red or red-orange deliquescent crystals.
Decomposes at 400C, loses 2H 2 O on prolonged heating at 100C.
Soluble in water; insoluble in alcohol. Noncombustible.
Chemical Properties of Sodium dichromate:
Sodium chromate, including the hexahydrate, is yellow crystalline solids that can also be used in solution.
Disodium dichromate (10588-01-9):
Uses of Sodium dichromate:
Colorimetry (copper determination), complex- ing agent, oxidation inhibitor in ethyl ether.
Sodium dichromate is red solid, soluble, powerful oxidizing agent, and consequently a fire hazard with dry carbonaceous materials.
Formed by acidifying sodium chromate solution, and then evaporating.
Sodium dichromate is used (1) in matches and pyrotechnics, (2) in leather tanning and in the textile industry, (3) as a source of chromate, cheaper than potassium dichromate.
General Description of Sodium dichromate:
Sodium dichromate is a red or red-orange crystalline solid.
Sodium dichromate may be strongly irritating to skin, eyes and mucous membranes.
Sodium dichromate is used as a corrosion inhibitor, and in the manufacture of other chemicals.
Air & Water Reactions of Sodium dichromate:
Deliquescent. Soluble in water.
Preparation of Sodium dichromate:
Sodium dichromate is generated on a large scale from ores containing chromium(III) oxides.
The ore is fused with a base, typically sodium carbonate, at around 1000 °C in the presence of air (source of oxygen):
2Cr2O3 + 4Na2CO3 + 3O2 -> 4Na2CrO4 + 4CO2
This step solubilizes the chromium and allows it to be extracted into hot water.
At this stage, other components of the ore such as aluminium and iron compounds, are poorly soluble.
Acidification of the resulting aqueous extract with sulfuric acid or carbon dioxide affords the dichromate:
2Na2CrO4 + 2CO2 + H2O -> Na2Cr2O7 + 2NaHCO3
2Na2CrO4 + H2SO4 -> Na2Cr2O7 + Na2SO4 + H2O
The dichromate is isolated as the dihydrate by crystallization.
In this way, many millions of kilograms of sodium dichromate are produced annually.
Since chromium(VI) is toxic, especially as the dust, such factories are subject to stringent regulations.
For example, effluent from such refineries is treated with reducing agents to return any chromium(VI) to chromium(III), which is less threatening to the environment.
A variety of hydrates of this salt are known, ranging from the decahydrate below 19.5 °C (CAS# 13517-17-4 ) as well as hexa-, tetra-, and dihydrates.
Above 62 °C, these salts lose water spontaneously to give the anhydrous material.
Sodium dichromate is crystallised around 30 to 35 degrees C.
Reactions of Sodium dichromate:
Dichromate and chromate salts are oxidizing agents.
For the tanning of leather, sodium dichromate is first reduced with sulfur dioxide.
In the area of organic synthesis, this compound oxidizes benzylic and allylic C-H bonds to carbonyl derivatives.
For example, 2,4,6-trinitrotoluene is oxidized to the corresponding carboxylic acid.
Similarly, 2,3-dimethylnaphthalene is oxidized by Na2Cr2O7 to 2,3-naphthalenedicarboxylic acid.
Secondary alcohols are oxidized to the corresponding ketone, e.g. menthol to menthone; dihydrocholesterol to cholestanone:
3 R2CHOH + Cr2O72− + 2 H+ → 3 R2C=O + Cr2O3 + 4 H2O
Relative to the potassium salt, the main advantage of sodium dichromate is its greater solubility in water and polar solvents like acetic acid.
Sodium dichromate can be used in fluorene to fluorenone conversion.
Na2Cr2O7 Uses (Sodium dichromate):
-Sodium dichromate is a primary material in the manufacturing of chromium chemicals.
-Sodium dichromate is used as textile dyes.
-Sodium dichromate is used in water treatment.
-Sodium dichromate is used in leather tanning.
-Sodium dichromate is used as a catalyst.
-Sodium dichromate is used as an oxidising agent in the manufacturing of synthetic organic chemicals.
-Sodium dichromate is used in the refining of petroleum.
-Sodium dichromate is used in metal treatments such as electro-engraving of copper.
-Sodium dichromate is used in Colorimetry experiment to determine the amount to copper.
-Sodium dichromate is used as an insecticide and fungicide.
-Sodium dichromate is used as a colourant in glass.
IUPAC name: Sodium dichromate
Other names: Chromic acid disodium salt
What is sodium dichromate?
Sodium dichromate is a red to orange crystalline solid. It is a member of a chemical group known as chromium (VI) compounds.
Other names for sodium dichromate include sodium bichromate, bichromate of soda and sodium dichromate (VI).
What is sodium dichromate used for?
Sodium dichromate is mainly used as a chemical intermediate in the production of other chromium compounds.
Sodium dichromate is also used in the production of dyes, as a bleaching agent and a corrosion inhibitor.
In the past sodium dichromate was used in wood preservatives.
How does sodium dichromate get into the environment?
Sodium dichromate may be released into the environment during its production and use.
How might I be exposed to sodium dichromate?
The general public may be exposure to very low levels of sodium dichromate as a contaminant in air or water.
Exposure to sodium dichromate is more likely to occur in the workplace.
However, safe limits are enforced to protect employees.
Such levels are below those that are thought to cause harmful effects.
CAS number: 7789-12-0
EC index number: 024-004-00-7
EC number: 234-190-3
Grade: ACS
Molar Mass: 278 g/mol
HS Code: 2841 30 00
Applications of Sodium dichromate:
Tanning leather, inorganic pigments, dyestuffs/stain (staining cotton/woolen fabric and color fixing of textile printing)
Raw material for other chromium compounds,Tanning of leather,Mordant for dyeing,Dyestuffs,Pigments
Oxidizing agent in organic syntheses,Catalysts,Metal finishing,Corrosion inhibitors.
Compound Formula: Cr2Na2O7
Molecular Weight: 261.97
Appearance : Orange or red crystalline solid
Melting Point: 357 °C
Boiling Point: 400 °C
Density: 2.35 g/cm3
Solubility in H2O: N/A
Exact Mass: 261.824956
Monoisotopic Mass: 261.824956
Sodium dichromate in aqueous sulfuric acid has been used since the turn of the century.
Sodium dichromate is a very strong oxidant; the use of this system to oxidize primary alcohols is severely limited by overoxidation, via the aldehyde hydrate, to the corresponding acid.
This problem can be partially circumvented in the preparation of volatile aldehydes (in particular aromatic aldehydes), by slow addition to excess alcohol and continuous removal of the aldehyde by distillation.
Oxidation of secondary alcohols that are reasonably soluble is acceptable, but milder methods are now available, and are discussed in detail later.
As may be expected, a totally aqueous system is also restricted by the low solubility of many potential substrates.
Hence several variations have subsequently been developed from this basic technique.
Sodium chromate and dichromate are the most important chromium products, used chiefly for manufacturing chromic acid and chromium pigments used in leather tanning and corrosion control.
Cr (III) is considered to be an essential trace metal in humans whereas various Cr (VI) compounds are classified as human carcinogens.
Human exposure to occupational chromium usually occurs through inhalation, and the severity depends upon the nature and function of the industry.
Inhalation of Cr compounds causes irritation of the respiratory tract with the bronchial tree being the primary target organ for carcinogenic effects of Cr (VI).
Inhalation of Cr-containing aerosols leads to perforations of the nasal septum, chronic bronchitis, decreased pulmonary function, pneumonia, and other respiratory effects.
Though inhalation is the major route of Cr exposure, other routes such as the gastrointestinal tract and skin may also be involved.
Nonoccupational Cr exposure may occur through automobile emissions and smoking cigarettes.
Consuming contaminated water and food may also contribute significantly to the Cr intoxication; however, surrounding industrial sources and the nature of the underlying soil determine the concentration of Cr in water.
CAS Number:
10588-01-9
7789-12-0 (dihydrate)
CHEBI: 39483
ChemSpider: 23723
ECHA InfoCard: 100.031.070
EC Number: 234-190-3
Gmelin Reference: 21597
PubChem CID: 25408
RTECS number:
HX7750000
HX7750000 (dihydrate)
UNII:
C9G6VY6ZZ4
52125XYY2A (dihydrate):
UN number: 3288
CompTox Dashboard (EPA): DTXSID8021274
Sodium dichromate, Na2Cr2O7·2H2O, is widely used when manufacturing chromium metal, magnetic tapes, tanning of leather, as a preservation compound for timber, metal finishing, pigments for plastic and ceramic industry, as well for corrosion prevention and in oil and detergent industry.
Sodium dichromate is obtained from ground chromite roasted with soda and oxidized, and then quenched with water.
Sodium dichromate is extracted with sulfuric acid to produce a commercially pure solution.
Sodium dichromate (solutions)
Sodium dichromate liquid solutions are an appropriate and cost-effective method of shipping bulk quantities.
Liquids are convenient because the need for manual handling (crystal dissolving) is not required.
Liquid sodium dichromate chemicals therefore offer a cleaner, safer and healthier working environment and can lower costs due to reduced housekeeping and maintenance requirements.
Chemical formula: Na2Cr2O7
Molar mass:
261.97 g/mol (anhydrous)
298.00 g/mol (dihydrate)
Appearance bright: orange
Odor: odorless
Density: 2.52 g/cm3
Melting point: 356.7 °C (674.1 °F; 629.8 K)
Boiling point: 400 °C (752 °F; 673 K) decomposes
Solubility in water: 73 g/100 mL at 25 °C
Solubility in other solvents: soluble in methanol, ethanol
Refractive index (nD): 1.661 (dihydrate)
Formula : Na2Cr2O7
Synonyms : Dichromic Acid Disodium Salt, Disodium Dichromate (VI), Sodium Pyrochromate, Chromium Salt.
Product description : Sodium dichromate comes as orange to red powder, hygroscopic product with a purity of 98.9% minimum.
Uses : main uses for sodium dichromate are surface treatment and leather tanning.
Sodium dichromate is also used as a strong oxidant in organic chemistry, as a corrosion inhibitor, in inks, dyes and pigments.
In surface treatment, sodium dichromate is used for passivation on stainless steel, steel and aluminum in acid baths.
Sodium dichromate
10588-01-9
Bichromate of soda
Disodium dichromate
Natriumdichromat
Sodium dichromate(VI)
UNII-C9G6VY6ZZ4
Dichromic acid, disodium salt
C9G6VY6ZZ4
disodium;oxido-(oxido(dioxo)chromio)oxy-dioxochromium
Celcure
Chromic acid (H2Cr2O7), sodium salt (1:2)
Caswell No. 761
Celcure Wood Presrvative
Natriumbichromaat
Natriumdichromaat
Natriumbichromaat [Dutch]
Natriumdichromaat [Dutch]
Natriumdichromat [German]
Koppers Wolman Salts CCA
Wolman Salts CCA-Type B
Wolman Salts CCA-Type C
Dichromate, sodium
Oakite Composition No. 155
Bichromate de sodium
Bichromate de sodium [French]
Wood Cure A Wood Preservative
HSDB 737
Osmose Hollow Heart Concentrate
Sodium(dichromate de)
Sodium(dichromate de) [French]
Sodio (dicromato di)
Sodio (dicromato di) [Italian]
Sodium dichromate (Na2(Cr2O7))
Na2Cr2O7
Chromium sodium oxide (Cr3Na2O7)
EINECS 234-190-3
Sodium dichromate solution
EPA Pesticide Chemical Code 06830
Dichromic acid, sodium salt
Chromic acid (H2Cr2O7), disodium salt
Dichromic acid (H2Cr2O7), disodium salt
CCRIS 8137
J. H. Baxter Chromated Zinc Chloride Solution
EINECS 252-062-5
Natriumdichromat(VI)
sodium dichromate(2-)
Sodium dichromate solution (70% or less)
Cr2O7.2Na
Na2[Cr2O7]
Sodium dichromate [Chromium and chromium compounds]
DTXSID8021274
CHEBI:39483
DICHROMIC ACID,SODIUM SALT
8506AF
AKOS015913934
34493-01-1
Q407873
Sodium dichromate [Wiki]
10588-01-9 [RN]
Bicromato di sodio [Italian]
C9G6VY6ZZ4
Dichromate de sodium [French]
dichromate, sodium
Natriumbichromaat [Dutch]
Natriumdichromaat [Dutch]
Natriumdichromat [German]
Sel disodique de l’acide dichromique [French]
Sodio (dicromato di) [Italian]
Sodium(dichromate de) [French]
二クロム酸ナトリウム [Japanese]
重铬酸钠 [Chinese]
[10588-01-9]
Bichromate de sodium [French]
Bichromate de sodium [French]
bichromate of soda
C016104
Celcure
CHEBI:39483
dichromic acid, disodium salt
dichromic acid, sodium salt
DICHROMIC ACID,SODIUM SALT
disodium (diketo-oxido-chromio)oxy-diketo-oxido-chromium
disodium dichromate
disodium oxido-(oxido-dioxochromio)oxy-dioxochromium
disodium oxido-(oxido-dioxo-chromio)oxy-dioxo-chromium
EINECS 234-190-3
J. H. Baxter Chromated Zinc Chloride Solution
Koppers Wolman Salts CCA
MFCD00003483
Na2[Cr2O7]
Na2Cr2O7
Natriumbichromaat [Dutch]
Natriumdichromaat [Dutch]
Natriumdichromat
Natriumdichromat [German]
Natriumdichromat(VI)
Oakite Composition No. 155
Osmose Hollow Heart Concentrate
Sodio (dicromato di) [Italian]
SODIUM BICHROMATE
Sodium dichromate solution (70% or less)
sodium dichromate(VI)
Sodium(dichromate de) [French]
UNII:C9G6VY6ZZ4
UNII-C9G6VY6ZZ4
Wolman Salts CCA-Type B
Wolman Salts CCA-Type C
Wood Cure A Wood Preservative