Chromium-compound manufacture
- Process role: Cr(VI) intermediate
- Critical parameters: Hydration state; assay; impurity profile; regulatory status
Sodium Dichromate (Na₂Cr₂O₇)
Sodium dichromate is a highly hazardous hexavalent-chromium oxidizer used as an intermediate or process chemical in selected chromium chemistry, surface treatment and specialty industrial operations. Anhydrous and dihydrate forms must be distinguished explicitly: they have different CAS numbers and molar masses. Procurement is dominated by Cr(VI) regulation, grade/purity, hydration state, impurity limits, dangerous-goods controls and authorized end use.
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CHEMISTRY, MANUFACTURING CONTEXT & MATERIAL BEHAVIOUR
The chromate/dichromate equilibrium depends strongly on pH: more acidic conditions favor dichromate/polychromate species, while more alkaline conditions favor chromate. Sodium dichromate is therefore both a source of Cr(VI) and a strong oxidizing process reagent. Hydration state is not a cosmetic distinction - it changes formula mass, assay basis and material balance.
PROCESS-ENGINEERING & GRADE-SELECTION CONSIDERATIONS
- Correct identity first: CAS 7775-11-3 belongs to sodium chromate, not sodium dichromate. Do not use it on an Na₂Cr₂O₇ page.
- State hydration form in the RFQ and COA. Anhydrous and dihydrate material cannot share one molar mass or water specification.
- Specify Na₂Cr₂O₇ assay on a clearly defined basis, plus moisture/water of crystallization and relevant Na/Cl/SO₄/insoluble or metal impurity limits according to process.
- Cr(VI) is heavily regulated. In the EU, sodium dichromate is listed in REACH Annex XIV; the buyer must verify whether the intended use is authorized, exempt or prohibited.
- Closed handling, dust control, segregation from reducing/combustible materials and compliant hazardous-waste management are mandatory engineering considerations.
◎ Technical Specifications
| Property | Value |
|---|---|
Formula |
Na₂Cr₂O₇ (anhydrous); Na₂Cr₂O₇·2H₂O (dihydrate) |
INDUSTRIAL APPLICATION MATRIX
Selected surface-treatment / plating chemistry
- Process role: Oxidizing / passivating chromium source in legacy or specialty processes
- Critical parameters: Process approval; purity; contamination limits; authorization
QUALITY CONTROL, COA PARAMETERS & TEST FOCUS
- Na₂Cr₂O₇ assay / Cr(VI) | Method/evidence: Redox titration / validated method | Why it matters: Primary active content
- Hydration / moisture | Method/evidence: Loss on drying / validated method | Why it matters: Identity, material balance and storage
- Sulfate / chloride | Method/evidence: Ion analysis / producer method | Why it matters: Process contamination control
- Sodium / metals | Method/evidence: ICP/AAS where required | Why it matters: Grade qualification
- Water-insoluble matter | Method/evidence: Gravimetric | Why it matters: Solution cleanliness
- Appearance / caking | Method/evidence: Visual | Why it matters: Storage condition and receiving screen
Why Choose OGSCM?
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On-time delivery with strong regional & global logistics.
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Strict quality control and batch consistency.
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Technical & commercial support throughout your procurement journey.
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Serving industries across GCC and MENA with local expertise.
Frequently Asked Questions
No. That CAS is associated with sodium chromate; sodium dichromate uses 10588-01-9 (anhydrous) and 7789-12-0 (dihydrate).
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