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Name: Ferrous Sulfate Heptahydrate

Molecular Formula: FeSO₄·7H₂O

CAS: 7782-63-0 | EINECS: 231-753-5

Molecular Weight: 278.02 | HS Code: 2833291000

Physical and Chemical Properties

1. Appearance: Light blue-green / pale green monoclinic crystals, commonly known as green vitriol; odorless with a salty-astringent taste.

2. Density: 1.898 g/cm³ (15°C); Melting point 64°C (loses 3 molecules of water of crystallization at this temperature).

3. Solubility: Soluble in water and glycerol; insoluble in ethanol; solubility at 20°C is approximately 25.6 g/100 mL; aqueous solution is acidic, pH ≈ 3.0–4.0.

4. Chemical Properties:

• Reducing property (key characteristic): Easily oxidized by oxygen in humid air; the surface gradually turns yellow-brown forming basic ferric sulfate (Fe³⁺), causing the product to become ineffective. In dry air, it undergoes efflorescence, releasing white powder.

• Upon heating: At 300°C, loses all water of crystallization to form anhydrous ferrous sulfate; further decomposition at high temperature produces iron oxide, sulfur dioxide, and sulfur trioxide (toxic fumes).

• Incompatible substances: Strong oxidizers and strong alkalis; exposure to light accelerates oxidative deterioration.

Product Grades

• Agricultural Grade: For fertilizer and soil improvement; Fe²⁺ ≥ 19%; purity 90–98%; 25 kg woven bag / bulk bag.

• Water Treatment / Industrial Grade: For sewage flocculation, decolorization, and reduction — the most commonly used grade; purity 90–98%.

• Feed Grade: Iron nutritional fortifier for animal feed; strict heavy metal limits.

• Reagent Grade (AR/CP): For laboratory analytical use.

• Food Grade: Iron fortifier for food products (limited application).

Main Applications

1. Water Treatment (Largest Application Field)

• Coagulant: Flocculation, phosphorus removal, decolorization, and COD removal in wastewater treatment plants; raw material for producing polyferric sulfate (PFS).

• Reducing agent: Reduction of hexavalent chromium (chromium-bearing wastewater), heavy metal treatment; arsenic removal in water treatment plants.

Advantage: Low cost. Disadvantage: Prone to oxidation — must be prepared fresh before use.

2. Agriculture / Horticulture

• Iron-supplementing fertilizer: Prevention and treatment of iron-deficiency chlorosis (gardenia, rose, fruit trees); supplies divalent iron to promote chlorophyll synthesis.

• pH adjustment: Lowers pH in alkaline soils; can kill moss and lichen; auxiliary control of fruit tree diseases (apple/pear scab, wheat smut).

Warning: Do NOT mix with alkaline fertilizers (quicklime, wood ash) — precipitation will render it ineffective.

3. Industrial Applications

• Pigments: Raw material for iron oxide red, Prussian blue, iron oxide black, and other iron oxide pigments.

• Textiles: Mordant; leather tanning and preservative.

• Battery / New Materials: Precursor raw material for lithium iron phosphate (LiFePO₄) production.

• Traditional: Raw material for iron gall ink (iron-tannin ink).

4. Pharmaceutical & Feed

• Pharmaceutical: Oral iron supplement for treating iron-deficiency anemia.

• Feed additive: Iron supplementation for animals to prevent iron-deficiency anemia.

Preparation Methods

Main industrial routes:

1. Titanium dioxide by-product method (the primary domestic source; ferrous sulfate is a byproduct of ilmenite processing for TiO₂ production).

2. Reaction of iron filings with dilute sulfuric acid: Fe + H₂SO₄(dilute) = FeSO₄ + H₂↑; cooling crystallization yields green vitriol crystals.

Storage and Packaging

• Packaging: 25 kg PP woven bag with PE film liner; bulk bag available; 25 kg bag is standard for export.

• Storage conditions: Cool, dry, and well-ventilated warehouse; MUST be sealed; protected from light and moisture; DO NOT store with oxidizers or alkalis.

• Shelf life: Due to susceptibility to oxidation, prolonged storage is not recommended — use within 6 months. Minor caking can be broken up and still used; severe yellow-brown discoloration indicates oxidative degradation and product failure.

VI. Safety Information (SDS Key Points)

GHS Signal Word: WARNING

• Harmful if swallowed; causes skin irritation; causes serious eye irritation; dust inhalation irritates the respiratory tract.

• Acute toxicity: Mouse oral LD50 = 1520 mg/kg.

• Operational protection: Wear dust mask, safety goggles, and acid/alkali-resistant gloves; avoid dust generation; wash hands after work.

• Spill handling: Collect solid material; do NOT flush directly into the sewer; for large spills, contain and collect.

• Firefighting: This product is non-flammable; in case of fire, use dry powder or sand — do NOT use direct water spray.