Iron Sulfide

Last Updated: June 28, 2024

Iron Sulfide

Iron(II) sulfide is a fascinating chemical compound that plays a significant role in various fields, including geology, chemistry, and industry. Made up of iron and sulfur, this compound is known for its dark, metallic appearance and is commonly found in the natural environment, especially within the earth’s crust. Iron(II) sulfide is formed when iron and sulfur combine in a specific ratio, creating a substance that is not only interesting for scientists to study but also has practical applications in everyday life. For example, it’s used in the production of sulfuric acid, in the iron and steel industry, and even in the preparation of certain pigments. Despite its simplicity, iron(II) sulfide’s unique properties make it an important material for various scientific and industrial processes.

What is Iron(II) Sulfide?

Iron(II) sulfide, represented chemically as FeS, is a distinct compound where iron and sulfur atoms bond in a one-to-one ratio. This compound is integral to the field of chemistry, showcasing the fascinating ways in which different elements can combine to form materials with unique properties. In its pure form, FeS exhibits a crystalline structure, showcasing the beauty and complexity of chemical reactions. Beyond its scientific intrigue, iron(II) sulfide has practical relevance in various applications, from environmental science to the manufacturing sector, underscoring its importance beyond the laboratory. It’s a prime example of how chemistry connects fundamental scientific principles with real-world uses, illustrating the transformative power of chemical compounds

Chemical Names and Formulas

Formula FeS
Name Ferrous sulfide
Alternate Names Ferrous sulfide (Iron(II) sulfide), Iron(II) sulfide, Iron monosulfide, Sulfanyliden iron, Thioxoiron

Structure of Iron(II) Sulfide

Structure of Iron(II) Sulfide

Iron(II) sulfide, or ferrous sulfide, is a compound formed by iron and sulfur in a 1:1 ratio, creating a crystal lattice where these atoms alternate. This structure is reminiscent of a grid made up of tiny balls, with each iron atom closely surrounded by sulfur atoms, facilitating a solid bond. This arrangement results in a solid material often found as the mineral pyrrhotite, characterized by a metallic luster and magnetic properties.

The crystalline form of iron(II) sulfide features a layered structure that contributes to its unique characteristics, such as its brittle nature and limited electrical conductivity, differentiating it from pure metals. FeS is not only crucial in various industrial applications but also plays a significant role in the iron-sulfur world theory, suggesting a possible pathway for the origin of life on Earth through simple reactions involving iron and sulfur compounds.

Preparation of Iron(II) Sulfide

Iron(II) sulfide, or FeS, is made by directly combining iron and sulfur. To do this safely in a lab, mix 7 grams of iron powder with 4 grams of sulfur in a porcelain crucible. This mixture is based on the chemical reaction ensuring the right balance between the iron and sulfur.

Fe + S → FeS

Once mixed, the crucible is heated slowly at first to prevent the mixture from splattering. As the heat increases, the sulfur melts, coats the iron, and eventually, the mix glows brightly, indicating the reaction has occurred. After cooling, the result is iron(II) sulfide, a metallic solid that doesn’t dissolve in water. This process requires careful handling, including wearing gloves and goggles, and working in a well-ventilated area to avoid inhaling toxic gases.

The preparation of iron(II) sulfide demonstrates an important chemical principle: the reaction between iron and sulfur is exothermic, releasing heat. This reaction is not only a fascinating example of how two elements combine to form a new compound but also shows the practical application of stoichiometry, the part of chemistry that studies the amounts of substances that react and form in chemical reactions. Iron(II) sulfide has various uses, including in the synthesis of other chemicals, in the iron and steel industries, and for educational demonstrations in chemistry classes. Its preparation, while simple, offers a clear window into the world of chemical synthesis and the careful balance and precautions necessary in any chemical experiment.

Physical Properties of Iron(II) Sulfide

Property Description
Appearance Dark, gray to black solid
Molecular Formula FeS
Molar Mass 87.91 g/mol
Density 4.84 g/cm³
Melting Point 1195°C (2183°F)
Boiling Point Decomposes before boiling
Solubility Insoluble in water; slightly soluble in acid
Hardness Brittle, with a Mohs hardness of 4-4.5
Electrical Conductivity Conductive, due to metallic bonding
Magnetic Properties Ferromagnetic at temperatures below its Curie point
Thermal Stability Stable under normal conditions but decomposes upon heating to sulfur dioxide and iron under high temperatures

Chemical Properties of Iron(II) Sulfide

Reactivity with Acids

Iron(II) sulfide reacts with acids, forming hydrogen sulfide gas (H₂S) and an iron(II) salt. For example:

    • Reaction with Hydrochloric Acid  : FeS+2HCl→FeCl+H₂S

This demonstrates how FeS can generate hydrogen sulfide gas.

Reactivity with Oxygen

Exposed to oxygen, FeS oxidizes, forming iron(III) oxide and sulfur dioxide:

This reaction indicates FeS’s role in the sulfur cycle and its susceptibility to weathering.

Solubility in Water

FeS is insoluble in water. It doesn’t dissolve but can form minerals like pyrite in specific conditions.

Thermal Stability

FeS decomposes when heated in air, producing sulfur dioxide and iron(III) oxide:

4FeS+7O₂ →2Fe₂O₃​+4SO₂

This occurs around 600°C, useful in metal extraction.

Magnetic Properties

FeS is weakly magnetic. This allows magnetic separation from non-magnetic substances, aiding in mineral processing.

Environmental Impact

FeS’s oxidation releases sulfur dioxide and iron(III) compounds. This can lead to acid mine drainage, affecting water bodies and aquatic life negatively.

Iron(II) Sulfide (FeS) Chemical Compound Information

Chemical Identifiers

Property Value
CAS Registry Number 1317-37-9
PubChem Compound ID 14828
SMILES Identifier [Fe]=S
MDL Number MFCD00011013

Uses of Iron(II) Sulfide

Uses Of Iron(II) sulfide (FeS)

In Sulfuric Acid Production

Iron(II) sulfide plays a crucial role in making sulfuric acid. It reacts with oxygen to produce sulfur dioxide, which is then transformed into sulfuric acid. This acid is essential for making fertilizers, in petroleum processing, and chemical manufacturing.

As a Desulfurization Agent

FeS helps remove sulfur from coal and oil, cutting down sulfur dioxide emissions. This process is vital for reducing air pollution and combating acid rain.

In the Alloy Industry

Adding iron(II) sulfide to metal alloys improves their strength, durability, and corrosion resistance. This enhancement is critical for materials used in construction, automotive, and aerospace sectors.

For Pesticides and Fertilizers

In agriculture, FeS is a key ingredient in producing pesticides and fertilizers. It supplies essential nutrients to plants and helps manage crop-damaging pests, boosting agricultural productivity.

In Battery Production

FeS shows promise in battery technology, especially for lithium and sodium-sulfur batteries. Its conductive properties could lead to more efficient, durable, and eco-friendly batteries.

In Earth Science

Iron(II) sulfide aids in paleomagnetic studies by retaining magnetic properties. These properties offer insights into the Earth’s past magnetic fields and geological activities.

Benefits Of Iron(II) Sulfide

Industrial Use

  • Metal Processing: FeS helps extract metals and make sulfuric acid.
  • Catalysis: It speeds up chemical production, improving process efficiency.

Environmental Cleanup

  • Heavy Metal Removal: FeS cleans water by removing heavy metals.
  • Nutrient Release: It plays a role in the sulfur cycle, enriching soils and aiding plant growth.

Energy Production

  • Hydrogen Sulfide Source: FeS is used to produce H2S for various industries.
  • Battery Technology: It’s being studied for use in batteries, promising better energy storage.

Scientific Research

  • Fossil Preservation: FeS helps preserve fossils over millions of years.
  • Geological Insights: Its presence in rocks tells us about past environments.


  • Soil Improvement: Adding FeS can adjust soil pH, benefiting crop growth.


  • Lower Risk: FeS is safer to handle than many sulfur compounds, reducing hazards.

Side Effects Of Iron(II) Sulfide

Environmental Impact

  • Acid Mine Drainage: When FeS is exposed to air and water, it can produce sulfuric acid, leading to acid mine drainage. This phenomenon can harm aquatic life and water quality.
  • Soil Acidification: FeS oxidation can also acidify soils, impacting plant growth and soil health.

Health Hazards

  • Hydrogen Sulfide Gas: Reacting FeS with acids releases hydrogen sulfide (H2S), a toxic gas. H2S exposure can cause respiratory issues and, in high concentrations, can be fatal.
  • Dust Inhalation: Inhaling FeS dust can irritate the respiratory system, causing coughing and shortness of breath.

Safety Risks

  • Fire Hazard: FeS dust is flammable and, when mixed with air, can form explosive mixtures.
  • Corrosion: FeS can accelerate the corrosion of metal structures, especially in humid environments, posing risks to infrastructure.

Handling Concerns

  • Safe Storage: FeS must be stored properly to prevent unwanted reactions with air or moisture.
  • Personal Protective Equipment (PPE): Proper PPE is necessary to handle FeS safely, including gloves, masks, and eye protection.


Is FeS₂ a Sulfide?

Yes, FeS2 is a sulfide known as iron disulfide, commonly found as the mineral pyrite.

What is the Correct Name for FeS₂?

The correct name for FeS2 is iron disulfide, often referred to as pyrite or fool’s gold.

Why is it Iron(II) Sulfide?

FeS, with one sulfur atom, is iron(II) sulfide because iron has a +2 oxidation state, forming a 1:1 ratio with sulfur.

Is FeS₂ an Ionic Compound?

FeS2, or iron disulfide, has covalent characteristics due to the sharing of electrons between iron and sulfur atoms.

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