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Send EmailSodium Chromate, Sodium Monochromate, Chromium Disodium Oxide, 7775-11-3, 12680-48-7
SODIUM CHROMATE (Na₂CrO₄)
Chromium Disodium Oxide / Sodium Monochromate / Chromium Sodium
CAS Numbers: 7775-11-3 (Anhydrous), 12680-48-7 (Hydrate)
EC Number: 231-889-5
1. IDENTIFICATION
| Property | Information |
|---|---|
| Chemical Name | Sodium Chromate |
| Synonyms | Chromium disodium oxide, Sodium monochromate, Chromium sodium, Chromic acid disodium salt |
| Chemical Formula | Na₂CrO₄ |
| Molecular Weight | 161.97 g/mol |
| CAS Numbers | 7775-11-3 (Anhydrous) 12680-48-7 (Hydrate) |
| EC Number (EINECS) | 231-889-5 |
| Appearance | Yellow to pale yellow crystalline solid |
| Odor | Odorless |
| Taste | Bitter, metallic taste |
2. PHYSICAL PROPERTIES
| Property | Value |
|---|---|
| Physical State (20°C) | Solid (crystalline) |
| Appearance | Yellow to pale yellow, orthorhombic crystals |
| Odor | Odorless |
| Taste | Bitter, metallic taste |
| Molecular Weight | 161.97 g/mol |
| Density (20°C) | 2.70 g/cm³ |
| Melting Point | 762 °C (1,404 °F) |
| Boiling Point | Decomposes above 1,000°C |
| Solubility in Water (25°C) | 87.6 g/100 g water (very high) |
| Solubility in Methanol | Slightly soluble |
| Solubility in Ethanol | Slightly soluble |
| pH (1% solution) | 10 – 12 (strongly alkaline) |
| Hygroscopicity | Hygroscopic – absorbs moisture from air |
| Crystal Form | Orthorhombic (anhydrous), tetrahydrate (hydrate) |
3. CHEMICAL PROPERTIES
| Property | Information |
|---|---|
| Chemical Formula | Na₂CrO₄ |
| Molecular Weight | 161.97 g/mol |
| Chromium (Cr) Content | ~32.1% (as Cr(VI)) |
| Sodium (Na) Content | ~28.4% |
| Oxygen (O) Content | ~39.5% |
| Oxidation State | Cr(VI) (hexavalent chromium) – highly toxic and carcinogenic |
| pH (1% solution) | 10 – 12 (strongly alkaline) |
| Stability | Stable under normal storage conditions |
| Oxidizing Properties | Strong oxidizer |
| Reaction with Acids | Converts to dichromate: 2 Na₂CrO₄ + H₂SO₄ → Na₂Cr₂O₇ + Na₂SO₄ + H₂O |
| Reaction with Reductants | Violent reactions, may cause fire or explosion |
| Incompatible Materials | Organic materials, reducing agents, combustible materials, acids |
Equilibrium in Solution (Chromate – Dichromate):
2 CrO₄²⁻ (yellow) + 2 H⁺ ⇌ Cr₂O₇²⁻ (orange) + H₂O
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Alkaline solution: CrO₄²⁻ (yellow, chromate dominant)
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Acidic solution: Cr₂O₇²⁻ (orange, dichromate dominant)
Conversion to Dichromate:
2 Na₂CrO₄ + H₂SO₄ → Na₂Cr₂O₇ + Na₂SO₄ + H₂O
4. HYDRATE FORMS
| Form | Formula | CAS | Appearance | Properties |
|---|---|---|---|---|
| Anhydrous | Na₂CrO₄ | 7775-11-3 | Yellow crystals | Hygroscopic |
| Tetrahydrate | Na₂CrO₄·4H₂O | 12680-48-7 | Yellow crystals | More stable |
| Hexahydrate | Na₂CrO₄·6H₂O | – | Yellow crystals | Less common |
5. PRODUCTION PROCESS
| Stage | Description |
|---|---|
| 1. Raw Material | Chromite ore (FeCr₂O₄) |
| 2. Roasting | Chromite ore is roasted with soda ash (Na₂CO₃) and lime in a reverberatory furnace with air |
| 3. Reaction | 4 FeCr₂O₄ + 8 Na₂CO₃ + 7 O₂ → 8 Na₂CrO₄ + 2 Fe₂O₃ + 8 CO₂↑ |
| 4. Leaching | Roasted product is leached with water |
| 5. Filtration | Insoluble impurities (iron oxides) are removed |
| 6. Acidification | Small amount of acetic acid is added to adjust pH |
| 7. Concentration | Solution is concentrated by evaporation |
| 8. Crystallization | Sodium chromate crystallizes |
| 9. Centrifugation | Crystals are separated |
| 10. Drying & Packaging | Product is dried and packaged |
Reaction Equation:
4 FeCr₂O₄ + 8 Na₂CO₃ + 7 O₂ → 8 Na₂CrO₄ + 2 Fe₂O₃ + 8 CO₂↑
6. APPLICATIONS
6.1. Production of Sodium Dichromate (Primary Use – Largest)
| Application | Function |
|---|---|
| Sodium Dichromate Production | Main precursor for sodium dichromate (Na₂Cr₂O₇) |
| Chromic Acid Production | Indirect precursor for chromic acid |
| Chromium Compounds | Raw material for other chromium compounds |
6.2. Corrosion Inhibition
| Application | Function |
|---|---|
| Cooling Water Systems | Corrosion inhibitor in industrial cooling systems |
| Geothermal Power Plants | Prevents corrosion in geothermal energy systems |
| Metal Treatment | Passivation of metal surfaces |
| Antifreeze Formulations | Corrosion inhibitor in automotive antifreeze |
6.3. Pigments & Dyes
| Application | Function |
|---|---|
| Chrome Yellow | PbCrO₄ – yellow pigment for paints and inks |
| Chrome Orange | Orange pigment |
| Chrome Green | Mixed pigment |
| Textile Dyeing | Mordant for wool dyeing |
6.4. Wood Preservation
| Application | Function |
|---|---|
| Wood Treatment | Protects against decay, fungal growth, and insect damage |
| CCA Component | Component in chromated copper arsenate (CCA) wood preservatives |
6.5. Oil & Gas Drilling
| Application | Function |
|---|---|
| Drilling Fluids | Corrosion inhibitor, biocide |
| Workover Fluids | Corrosion protection |
6.6. Paints & Inks
| Application | Function |
|---|---|
| Paint Manufacturing | Component in anti-corrosive paints |
| Printing Inks | Pigment component |
| Metal Coatings | Corrosion-resistant coatings |
6.7. Insecticides & Pesticides
| Application | Function |
|---|---|
| Insecticide Production | Raw material for certain insecticides |
| Pesticide Formulations | Component in pesticide formulations |
6.8. Catalysis & Organic Synthesis
| Application | Function |
|---|---|
| Catalyst | Oxidation catalyst in organic synthesis |
| Chemical Intermediate | Intermediate for various chemical processes |
6.9. Textile Industry
| Application | Function |
|---|---|
| Wool Dyeing | Mordant for fixing dyes to wool fibers |
| Fabric Treatment | Oxidation treatment for fabrics |
6.10. Other Applications
| Application | Function |
|---|---|
| Leather Tanning | Intermediate for chrome tanning (via dichromate) |
| Photography | Component in photographic processes |
| Pyrotechnics | Oxidizing agent in fireworks |
| Ceramics | Colorant for ceramic glazes |
| Glass Manufacturing | Colorant for green glass |
7. CONVERSION TO DICHROMATE
| Parameter | Information |
|---|---|
| Reaction | 2 Na₂CrO₄ + H₂SO₄ → Na₂Cr₂O₇ + Na₂SO₄ + H₂O |
| Conditions | Acidification with sulfuric acid |
| Product | Sodium dichromate (Na₂Cr₂O₇) – orange-red crystals |
| Application | Sodium dichromate is the precursor for most other chromium compounds |
8. QUALITY SPECIFICATIONS (TECHNICAL GRADE)
| Parameter | Specification |
|---|---|
| Purity (Na₂CrO₄) | ≥ 98.0% |
| Cr(VI) Content | ~32.1% |
| Chlorides (Cl) | ≤ 0.05% |
| Sulfates (SO₄) | ≤ 0.10% |
| Iron (Fe) | ≤ 0.01% |
| Water Insolubles | ≤ 0.05% |
| Moisture | ≤ 0.5% |
| pH (1% solution) | 10 – 12 |
9. STORAGE & HANDLING
| Parameter | Information |
|---|---|
| Storage Conditions | Cool, dry, well-ventilated area |
| Container Requirements | Tightly closed, corrosion-resistant containers (HDPE, lined drums) |
| Protect From | Moisture (hygroscopic), organic materials, reducing agents, acids |
| Shelf Life | 12-24 months (when stored properly in unopened packaging) |
| Hygroscopicity | Hygroscopic – absorbs moisture from air |
| Incompatible Materials | Organic materials, reducing agents, combustible materials, acids |
| Packaging Options | 25 kg drums (HDPE), 50 kg drums, 500 kg/1000 kg FIBC (big bags) |
10. SAFETY & HEALTH INFORMATION (GHS CLASSIFICATION)
| Hazard Class | Category |
|---|---|
| Oxidizing Solids | Category 2 (H272) |
| Acute Toxicity (Oral) | Category 4 (H302) |
| Acute Toxicity (Inhalation) | Category 2 (H330) |
| Skin Corrosion/Irritation | Category 2 (H315) |
| Serious Eye Damage | Category 1 (H318) |
| Respiratory Sensitization | Category 1 (H334) |
| Skin Sensitization | Category 1 (H317) |
| Germ Cell Mutagenicity | Category 1B (H340) |
| Carcinogenicity | Category 1A (H350) |
| Reproductive Toxicity | Category 2 (H361) |
| Specific Target Organ Toxicity (Repeated exposure) | Category 1 (H372) |
| Acute Aquatic Toxicity | Category 1 (H400) |
| Chronic Aquatic Toxicity | Category 1 (H410) |
11. HAZARD STATEMENTS (H-CODES)
| Code | Statement |
|---|---|
| H272 | May intensify fire; oxidizer |
| H302 | Harmful if swallowed |
| H315 | Causes skin irritation |
| H317 | May cause an allergic skin reaction |
| H318 | Causes serious eye damage |
| H330 | Fatal if inhaled |
| H334 | May cause allergy or asthma symptoms if inhaled |
| H340 | May cause genetic defects |
| H350 | May cause cancer |
| H361 | Suspected of damaging fertility or the unborn child |
| H372 | Causes damage to organs through prolonged or repeated exposure |
| H400 | Very toxic to aquatic life |
| H410 | Very toxic to aquatic life with long-lasting effects |
12. PRECAUTIONARY STATEMENTS (P-CODES)
| Code | Statement |
|---|---|
| P201 | Obtain special instructions before use |
| P202 | Do not handle until all safety precautions have been read and understood |
| P210 | Keep away from heat, sparks, open flames |
| P220 | Keep away from combustible materials |
| P260 | Do not breathe dust |
| P280 | Wear protective gloves, protective clothing, eye protection, face protection |
| P301+P312 | IF SWALLOWED: Call a POISON CENTER if you feel unwell |
| P302+P352 | IF ON SKIN: Wash with plenty of water |
| P304+P340 | IF INHALED: Remove person to fresh air |
| P305+P351+P338 | IF IN EYES: Rinse cautiously with water for several minutes |
| P308+P313 | IF exposed or concerned: Get medical advice |
| P501 | Dispose of contents/container in accordance with local regulations |
13. TOXICOLOGICAL INFORMATION
| Parameter | Value |
|---|---|
| Oral LD50 (rat) | ~1,000 – 2,000 mg/kg (moderate toxicity) |
| Dermal LD50 (rabbit) | > 2,000 mg/kg |
| Inhalation LC50 (rat) | Not established (very toxic) |
| Carcinogenicity | IARC Group 1 (Carcinogenic to humans) |
| Mutagenicity | Positive – causes genetic mutations |
| Reproductive Toxicity | Suspected reproductive toxicant |
| Target Organs | Respiratory system, skin, eyes, kidneys, liver |
| Chronic Effects | Lung cancer, nasal septum perforation, dermatitis, kidney damage |
Health Effects:
-
Acute (Ingestion): Nausea, vomiting, diarrhea, abdominal pain, gastrointestinal bleeding, acute renal failure
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Acute (Inhalation): Respiratory tract irritation, coughing, wheezing, pulmonary edema
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Acute (Skin Contact): Irritation, dermatitis, sensitization
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Acute (Eye Contact): Severe irritation, potential eye damage
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Chronic: Lung cancer, nasal ulcers and perforation, chronic dermatitis, liver and kidney damage
14. FIRST AID MEASURES
| Exposure Route | Action |
|---|---|
| Inhalation | Remove to fresh air. Administer oxygen if breathing difficulty. Seek immediate medical attention. |
| Skin Contact | Remove contaminated clothing. Wash with plenty of water for at least 15 minutes. Seek medical attention. |
| Eye Contact | Rinse immediately with plenty of water for at least 15 minutes. Seek immediate medical attention. |
| Ingestion | Do NOT induce vomiting. Rinse mouth. Drink water. Seek immediate medical attention. |
15. FIRE FIGHTING MEASURES
| Parameter | Information |
|---|---|
| Fire Hazard | Oxidizer – may cause fire or explosion when in contact with combustible materials |
| Extinguishing Media | Water spray (large quantities), dry sand, CO₂ (for small fires) |
| Special Hazards | Decomposes when heated, releasing toxic chromium fumes and oxygen |
| Protective Equipment | Self-contained breathing apparatus (SCBA), full protective clothing |
16. ENVIRONMENTAL INFORMATION
| Parameter | Information |
|---|---|
| Aquatic Toxicity | Very toxic to aquatic life with long-lasting effects |
| Persistence | Persistent in environment (Cr(VI) does not degrade) |
| Bioaccumulation | Moderate potential |
| Mobility in Soil | High (soluble in water) |
| Waste Disposal | Dispose as hazardous waste according to local regulations. Do not discharge into natural water bodies. |
17. TRANSPORT INFORMATION
| Parameter | Information |
|---|---|
| UN Number | 3086 (Toxic solid, oxidizing, n.o.s.) |
| Hazard Class | 5.1 (Oxidizing substance) |
| Subsidiary Hazard | 6.1 (Toxic substance) |
| Packing Group | II |
| Proper Shipping Name | TOXIC SOLID, OXIDIZING, N.O.S. (Sodium chromate) |
| Marine Pollutant | Yes |
| ADR/RID Label | 5.1 + 6.1 |
| EMS | F-A, S-Q |
18. REGULATORY INFORMATION
| Region | Status |
|---|---|
| EU | REACH registered; restricted under Annex XVII (SVHC – Substance of Very High Concern) |
| Turkey (KKDIK) | Mandatory compliance; requires registration |
| USA (TSCA) | Listed; subject to reporting |
| Canada (DSL) | Listed |
| Australia (AICS) | Listed |
| Japan (ENCS) | Listed |
| Korea (KECL) | Listed |
| China (IECSC) | Listed |
| RoHS | Restricted in electrical and electronic equipment |
19. SYNONYMS & OTHER NAMES
| Turkish Name | English Name |
|---|---|
| Sodyum Kromat | Sodium Chromate |
| Krom Disodyum Oksit | Chromium Disodium Oxide |
| Sodada Kromat | Soda Chromate |
| Krom Sodyum Oksit | Chromium Sodium Oxide |
| Sodyum Monokromat | Sodium Monochromate |
| Kromyum Sodyum | Chromium Sodium |
Database Identifiers:
-
CAS (Anhydrous): 7775-11-3
-
CAS (Hydrate): 12680-48-7
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EC: 231-889-5
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MDL: MFCD00003488
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PubChem CID: 24904
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RTECS: GB2955000
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UN: 3086
20. SUMMARY & IMPORTANT NOTES
SUMMARY:
Sodium Chromate (Na₂CrO₄, CAS 7775-11-3) is a yellow, crystalline, hygroscopic, and strong oxidizing agent containing hexavalent chromium (Cr(VI)). It is classified as an IARC Group 1 carcinogen and is highly toxic to human health and the environment.
Key Features:
| Feature | Value |
|---|---|
| Appearance | Yellow crystalline solid |
| Molecular Weight | 161.97 g/mol |
| Density | 2.70 g/cm³ |
| Melting Point | 762°C |
| Water Solubility (25°C) | 87.6 g/100 g water |
| pH (1% solution) | 10-12 (strongly alkaline) |
Main Application Areas:
| Sector | Applications |
|---|---|
| Sodium Dichromate Production | Primary precursor for dichromate and other chromium compounds |
| Corrosion Inhibition | Cooling water systems, geothermal power plants, antifreeze |
| Pigments & Dyes | Chrome yellow, chrome orange, textile mordant |
| Wood Preservation | Component in wood preservatives |
| Oil & Gas | Drilling fluids corrosion inhibitor |
| Paints & Inks | Anti-corrosive paints, printing inks |
| Insecticides | Raw material for insecticide production |
Key Safety Points:
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CARCINOGEN (Category 1A) – May cause cancer (lung cancer)
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MUTAGEN – May cause genetic defects
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REPRODUCTIVE TOXIN – Suspected of damaging fertility
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TOXIC – Fatal if inhaled; harmful if swallowed
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CORROSIVE – Causes serious eye damage
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ENVIRONMENTAL HAZARD – Very toxic to aquatic life
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OXIDIZER – Keep away from combustible materials
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HANDLE WITH EXTREME CAUTION – Use full PPE, adequate ventilation
IMPORTANT NOTES:
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Hexavalent Chromium (Cr(VI)) Hazard: Sodium chromate contains hexavalent chromium, classified as IARC Group 1 carcinogen (carcinogenic to humans). Associated with lung cancer, nasal septum perforation, and skin ulcers.
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Primary Precursor for Chromium Compounds: Sodium chromate is the starting material for the production of sodium dichromate, which is then used to produce most other chromium compounds (chromic acid, chromium pigments, chrome tanning agents).
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Chromate-Dichromate Equilibrium: In aqueous solution, chromate (yellow, CrO₄²⁻) and dichromate (orange, Cr₂O₇²⁻) exist in equilibrium. Alkaline conditions favor chromate; acidic conditions favor dichromate.
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Alkaline Nature: Sodium chromate solutions are strongly alkaline (pH 10-12 at 1% concentration). This alkalinity contributes to its corrosive properties.
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Hygroscopic: Sodium chromate is hygroscopic and absorbs moisture from air. Store in tightly sealed containers to prevent caking and degradation.
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Geothermal Applications: Sodium chromate is used as a corrosion inhibitor in geothermal power plants, where high temperatures and aggressive brines cause severe corrosion.
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Alternatives: Due to toxicity concerns, alternatives are being developed for many applications:
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Corrosion inhibition: Molybdate-based inhibitors, nitrites
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Wood preservation: Copper-based preservatives (copper azole, alkaline copper quaternary)
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Regulatory Restrictions: Sodium chromate is restricted under REACH (EU), RoHS, and many national regulations. It is listed as a Substance of Very High Concern (SVHC).
-
Personal Protective Equipment: When handling sodium chromate, always use:
-
Nitrile or neoprene gloves (not latex)
-
Chemical safety goggles + face shield
-
Full protective clothing
-
Respiratory protection (N100 or P100 respirator)
-
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Medical Surveillance: Workers handling chromium(VI) compounds should undergo regular medical surveillance, including lung function tests, skin examinations, and nasal septum inspections.
Important Disclaimer: This Technical Data Sheet (TDS) is for informational purposes only. For complete safety, handling, storage, and regulatory compliance information, always refer to the official Safety Data Sheet (SDS) provided by the manufacturer/supplier. Sodium chromate is an extremely hazardous substance. Extreme caution must be exercised during handling, storage, and disposal.
