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Ferrous sulfate heptahydrate (FeSO₄·7H₂O) is a crystalline iron(II) salt widely used in various sectors including agriculture, medicine, water treatment, and industrial processes.
Its hydrated form is characterized by its distinctive blue-green crystals.
It serves as a key source of bioavailable iron and is involved in a multitude of redox-driven chemical and biological processes.
CAS Number: 7782-63-0
Synonyms:
Iron(II) sulfate heptahydrate,Green vitriol,Copperas,Iron monosulfate heptahydrate
Sulfuric acid, iron(2+) salt (1:1), heptahydrate
Natural Occurrence and Geological Sources
Ferrous sulfate naturally occurs as the mineral melanterite, primarily found in oxidized zones of iron sulfide ores (e.g., pyrite). It forms under acidic and humid conditions, commonly in post-mining environments and acid mine drainage systems.
Synthesis and Industrial Production
Industrial production primarily involves:
Roasting of pyrite (FeS₂) followed by leaching with sulfuric acid.
By-product of steel pickling in H₂SO₄.
Reaction:
Fe + H₂SO₄ → FeSO₄ + H₂↑
FeSO₄ (aq) + 7H₂O → FeSO₄·7H₂O (crystallized)
Crystallization from aqueous solutions yields the heptahydrate form.
Analytical Characterization Techniques
X-ray diffraction (XRD) for crystalline structure
Fourier-transform infrared spectroscopy (FTIR) for sulfate and water bonding
Thermogravimetric analysis (TGA) for hydration levels
UV-Vis spectroscopy for Fe²⁺ detection
ICP-OES and AAS for elemental iron quantification
Crystallography and Hydration Dynamics
Ferrous sulfate heptahydrate crystallizes in the monoclinic system, space group P21/c.
Upon heating, it undergoes stepwise dehydration, transitioning to tetrahydrate, monohydrate, and finally to anhydrous FeSO₄.
Thermodynamic and Kinetic Behavior
ΔH_soln (enthalpy of dissolution): ~ -61 kJ/mol
Dehydration steps:
30–60 °C → loss of 1–3 H₂O
100–150 °C → tetrahydrate to monohydrate
300 °C → decomposition to Fe₂O₃ and SO₂
Redox: Fe²⁺ is prone to oxidation to Fe³⁺ in the presence of O₂.
Solubility and Dissociation Mechanism
In aqueous solution:
FeSO₄·7H₂O → Fe²⁺ + SO₄²⁻ + 7H₂O
Fe²⁺ ions are weakly acidic and can form hydroxo-complexes in alkaline conditions.
Redox Chemistry and Reactivity
Fe²⁺ acts as a reducing agent, commonly used in:
Reduction of chromates
Fenton’s reagent: Fe²⁺ + H₂O₂ → Fe³⁺ + OH• + OH⁻
Soil redox buffering
Applications in Water Treatment
Used as:
Coagulant/flocculant
Phosphate precipitant to reduce eutrophication
Odor control agent in wastewater systems
Uses in Agriculture and Fertilizers
Micronutrient supplement in soils deficient in iron
Corrects iron chlorosis in crops
Applied via foliar spray or soil amendment
Role in Animal Feed and Veterinary Medicine
Source of bioavailable iron for ruminants, poultry, and swine
Supports hemoglobin synthesis and growth
Part of premix formulations
Importance in Human Health and Supplements
Treats iron-deficiency anemia
Common in oral tablets, capsules, and syrups
Typical adult dose: 325 mg (equiv. to 65 mg Fe²⁺)
Pharmaceutical Formulations and Uses
Sustained-release tablets
Combined with folic acid or vitamin C
Enteric coatings to reduce gastrointestinal side effects
Industrial Applications
Dye manufacture: Mordant in fabric dyeing
Cement additive: Enhances resistance to sulfate attack
Electroplating: Source of Fe²⁺ for baths
Environmental Applications
In situ chemical reduction for chromium(VI) remediation
Acid mine drainage treatment
Soil amendment for heavy metal immobilization
Biochemical Interactions and Iron Metabolism
Fe²⁺ is essential for:
Hemoglobin and myoglobin synthesis
Electron transport (cytochromes)
DNA synthesis via ribonucleotide reductase
SAFETY INFORMATION ABOUT FERROUS SULFATE HEPTAHYDRATE
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off conSAFETYtaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
