Ferrous Chloride Tetrahydrate, Iron (II) Chloride Tetrahydrate, 13478-10-9

FERROUS CHLORIDE TETRAHYDRATE (FeCl₂·4H₂O)

1. Chemical Identity and Material Classification

• Chemical Name: Ferrous Chloride Tetrahydrate, Iron(II) Chloride Tetrahydrate

• Synonyms: Iron Chloride Dihydrate (incorrect – 4H₂O is tetrahydrate), Ferrous Chloride Hydrated, Iron(II) Chloride 4H₂O, Iron Dichloride Tetrahydrate

• CAS Number: 13478-10-9

• Molecular Formula: FeCl₂·4H₂O

• Molecular Weight: 198.81 g/mol (tetrahydrate); 126.75 g/mol (anhydrous)

• EC Number: 603-870-5 (tetrahydrate); 231-843-4 (anhydrous)

• MDL Number: MFCD00149709

• RTECS Number: NO5600000

2. Chemical Structure and Molecular Characteristics

• Structure: Octahedral [Fe(H₂O)₄Cl₂] units (trans-configuration)

• Coordination geometry: Octahedral (Fe center coordinated to 4 H₂O and 2 Cl⁻ ligands)

• Oxidation state of iron: +2 (ferrous, reducing agent)

• Crystal system: Monoclinic (tetrahydrate form)

• Fe–O bond length (H₂O): ~2.10–2.15 Å

• Fe–Cl bond length: ~2.45–2.50 Å

• Color origin: Pale green due to d-d transitions (high-spin d⁶ configuration)

3. Physical Properties

3.1 General Physical Properties (Tetrahydrate)

3.2 Thermal Properties

4. Solubility Behavior

5. Aqueous Solution Chemistry

6. Production Methods

6.1 Direct Reaction of Iron with Hydrochloric Acid (Industrial Standard)

• Reaction: Fe (s) + 2HCl (aq) → FeCl₂ (aq) + H₂ (g)

• Process: Iron filings or scrap reacted with 20–30% HCl → exothermic reaction → filtration → evaporation → crystallization → tetrahydrate crystals

• Temperature control: Below 12.3°C for hexahydrate; above 12.3°C for tetrahydrate

• Anaerobic conditions: Required to prevent oxidation to Fe³⁺ (nitrogen blanket or excess iron present)

• Yield: ~90–95%

• Excess iron addition: Prevents Fe²⁺ oxidation during processing

6.2 From Ferric Chloride Reduction (Alternative)

• Reaction: 2FeCl₃ + Fe → 3FeCl₂

• Process: Iron metal added to FeCl₃ solution → reduction of Fe³⁺ to Fe²⁺ → crystallization

• Application: Recycling of waste FeCl₃ from PCB etching

6.3 From Iron Oxide and HCl (Alternative)

• Reaction: FeO + 2HCl → FeCl₂ + H₂O

• Process: Wüstite (FeO) or iron scale → dissolved in HCl → crystallization

6.4 Anhydrous Ferrous Chloride (Specialty)

• Reaction: Fe (s) + 2HCl (g) → FeCl₂ (s) + H₂ (g)

• Temperature: 500–900°C (gas phase reaction)

7. Redox Properties and Reducing Agent Mechanism

7.1 Standard Reduction Potentials

7.2 Reducing Ability

• Character: Moderate reducing agent (E° = 0.77 V for Fe²⁺ → Fe³⁺)

• Oxidation in air: Rapid in neutral/alkaline conditions, slower in acidic conditions (pH <3)

• Reaction with oxygen (neutral): 4Fe²⁺ + O₂ + 10H₂O → 4Fe(OH)₃ (s) + 8H⁺ (brown precipitate)

7.3 Reduction of Hexavalent Chromium (Cr⁶⁺ → Cr³⁺) – Water Treatment

• Reaction: 6Fe²⁺ + Cr₂O₇²⁻ + 14H⁺ → 6Fe³⁺ + 2Cr³⁺ + 7H₂O

• Application: Detoxification of chromate-containing wastewater

• Stoichiometry: 1 g Cr⁶⁺ requires ~3 g Fe²⁺ (as FeCl₂·4H₂O)

8. Electrochemical Parameters

9. Application Areas – Water and Wastewater Treatment

9.1 Hexavalent Chromium (Cr⁶⁺) Reduction (Primary Application)

9.2 Phosphate Removal (Co-precipitation)

9.3 Reduction of Other Oxidizing Pollutants

10. Application Areas – Other Industries

10.1 Chemical Industry (Reducing Agent and Catalyst)

10.2 Metallurgy and Electroplating

10.3 Textile and Dye Industry

10.4 Laboratory and Analytical Chemistry

10.5 Sewage Treatment

11. Comparison with Ferric Chloride (FeCl₃)

12. Product Forms and Specifications

12.1 Available Forms

12.2 Quality Specifications (Tetrahydrate, Technical Grade)

12.3 Quality Specifications (Reagent Grade, Tetrahydrate)

13. Analytical Methods

13.1 Total Iron Determination (Titration with KMnO₄)

13.2 Ferric Iron (Fe³⁺) Determination

13.3 Ferrous Iron (Fe²⁺) Determination

14. Safety and Toxicology

15. Safety Precautions and Personal Protective Equipment (PPE)

• Hazards:

  • Corrosive – causes skin burns and eye damage (R34)

  • Harmful if swallowed (R22)

  • Irritating to skin and eyes (R38, R41)

  • Oxidizes in air – exothermic

• Reactivity:

  • Incompatible with: strong oxidizing agents (nitrates, chromates, permanganates), alkali metals

  • Air-sensitive – oxidizes to Fe³⁺ (brown color)

  • Light-sensitive – store in dark or amber containers

  • Moisture-sensitive – hygroscopic

  • Corrosive to most metals

• PPE (mandatory):

  • Chemical-resistant gloves (nitrile or neoprene, minimum 0.4 mm thickness, EN 374)

  • Chemical splash goggles (EN 166) or face shield

  • Protective clothing (acid-resistant)

  • Respiratory protection (P2 filter – if dust or mist present)

• Engineering controls:

  • Local exhaust ventilation (LEV) for powder handling

  • Eyewash stations and safety showers within immediate vicinity

• First aid:

  • Inhalation: Remove to fresh air; seek medical attention if respiratory irritation occurs

  • Skin contact: Wash with soap and copious water for at least 15 minutes; remove contaminated clothing; seek medical attention

  • Eye contact: Rinse with water for 15–20 minutes, lifting eyelids; seek immediate medical attention

  • Ingestion: Rinse mouth; do NOT induce vomiting; give water or milk; seek immediate medical attention

16. Environmental Fate and Disposal

17. Storage and Shelf Life

• Storage conditions:

  • Cool, dry, well-ventilated area (15–25°C – temperature control recommended)

  • Keep tightly closed in original packaging (hygroscopic)

  • Protect from air (oxygen) – store under nitrogen if possible for long-term storage

  • Protect from light – use amber glass or opaque containers

  • Store away from oxidizing agents and alkali metals

  • Do not store near food or feed

  • Avoid contact with most metals (corrosive)

• Shelf life:

  • Tetrahydrate (sealed, under N₂): 12–24 months

  • In solution (acidic, pH <3): 3–6 months (may oxidize to Fe³⁺ and precipitate)

• Degradation indicator:

  • Solid: Yellow-brown discoloration (oxidation to Fe³⁺)

  • Solution: Change from pale green to yellow-brown, formation of brown precipitate (Fe(OH)₃)

18. Transport Information

19. Synonyms, Standards Compliance, and Why Choose Ferrous Chloride Tetrahydrate?

Synonyms

• English: Ferrous chloride tetrahydrate, Iron(II) chloride tetrahydrate, Iron dichloride tetrahydrate, Ferrous chloride hydrated

• Other languages:

  • Turkish: Demir(II) klorür tetrahidrat, Ferro klorür tetrahidrat

  • German: Eisen(II)-chlorid tetrahydrat

  • French: Chlorure de fer(II) tétrahydraté

  • Spanish: Cloruro ferroso tetrahidratado

Standards Compliance

Why Choose Ferrous Chloride Tetrahydrate? (Technical Summary)

• Effective reducing agent for Cr⁶⁺ (hexavalent chromium): >99% removal efficiency in wastewater treatment

• Lower corrosivity than FeCl₃: Easier handling, less aggressive to equipment

• Cost-effective: Similar cost to FeCl₃ but used in different applications

• Versatile reducing agent: Reduces chromates, permanganates, chlorinated organics, nitrates

• In-situ coagulant: Oxidation to Fe³⁺ in water produces Fe(OH)₃ floc (phosphorus removal, turbidity)

• Well-defined crystalline form: Tetrahydrate has consistent composition (vs. lower hydrates)

• High solubility in water (160 g/100 mL): Allows concentrated solutions for rapid reactions

• Essential analytical reagent: Used in selenium detection and redox titrations

• Limitation note: Air-sensitive – oxidizes to Fe³⁺ in storage; requires airtight, oxygen-free conditions for long-term stability. Light-sensitive – store in dark containers. Corrosive to eyes and skin.

• Storage advisory: For best results, use fresh material or store under inert gas (N₂ or Ar) with excess iron metal to maintain Fe²⁺ state.

20. Sectoral Suitability Summary Table

This TDS is prepared in compliance with ISO 11014-1 format and is intended for water treatment engineers, chemical process engineers, wastewater treatment plant operators, laboratory technicians, metallurgists, and procurement professionals. Certificates of Analysis (CoA), Safety Data Sheets (SDS), reduction test reports, and sample validation reports are available upon request.