The iron sulfide (II), also called ferrous sulfide, is a chemical compound of formula FeS. Powdered iron sulfide is pyrophoric (ignites spontaneously in air). This compound is obtained by heating sulfur and iron according to the reaction: Fe + S → FeS.
The reaction is very exothermic (it releases heat) and the ratio between iron and sulfur must be 7: 4 (NileRed, 2014).
Figure 1: Structure of iron (II) sulfide.
Ferrous sulfide can also be obtained in aqueous medium by dissolving sulfur in an ionic iron (II) solution. Sulfur, when dissolved, forms hydrogen sulfide that reacts reversibly with iron (II) ions according to the reaction Fe 2+ + H 2 S FeS (s) + 2H +
However, this reaction competes with the iron (II) acid sulfate formation reaction in the following way: Fe 2+ + 2HS− → Fe (HS) 2 (s)
Subsequently, the acidic iron (II) sulfate decomposes to ferrous sulfate, although the reaction occurs very slowly (Rickard, 1995).
Physical and chemical properties
Iron (II) sulfide is a dark brown or black solid with a metallic appearance. When pure, it is colorless (National Center for Biotechnology Information, SF). The appearance of ferrous sulfide is illustrated in Figure 2.
Figure 2: appearance of iron (II) sulfide.
The compound has a molecular weight of 87.910 g / mol and a density of 4.84 g / ml. It has a melting point of 1195 ° C and is insoluble in water and nitric acid (Royal Society of Chemistry, 2015).
Ferrous sulfide reacts in an acid medium to form ferrous oxide and hydrogen sulfide vapors that are extremely toxic. This is seen in the following reaction:
FeS + 2H + → Fe 2+ + H 2 S
Reacts with dilute solutions of sulfuric acid to form ferrous oxide, sulfur dioxide and water depending on the reaction:
FeS + H 2 SO 4 → FeO + H 2 O + SO 2
Reactivity and hazards
Ferrous Sulfide is an unstable compound and reacts with air to form ferrous oxide and sulfur. The compound is pyrophoric and can ignite spontaneously or also the product of a strong impact, so it is not advisable to crush it in a mortar when it is synthesized and it must be treated with care.
Reacts with oxidizing agents and when decomposition is heated emits toxic fumes of sulfur oxides. The compound is very dangerous in case of ingestion and dangerous in case of contact with the eyes (irritant) and inhalation (Material Safety Data Sheet Ferrous sulfide, 2013).
In case of contact with the eyes, they should be rinsed with plenty of water for at least 15 minutes, occasionally lifting the upper and lower eyelids.
If the compound comes into contact with the skin, it should be rinsed with plenty of water for at least 15 minutes while removing contaminated clothing and shoes.
If swallowed, if the victim is conscious and alert, 2-4 cups of milk or water should be given. Nothing should ever be given by mouth to an unconscious person
In case of inhalation, the victim should be removed from the place of exposure and moved to a cool place. If it is not breathing, artificial respiration should be given. If breathing is difficult, oxygen should be given.
In all cases, immediate medical attention should be obtained (fisher scientific, 2009).
Iron sulfide is involved in a rare benign condition known as pseudomelanosis duodeni. It manifests endoscopically as discrete, flat, black-brown spots on the duodenal mucosa.
It does not produce symptoms and can be reversible. With electron microscopy and electron probe energy scattering X-ray analysis, the pigment corresponds mainly to an accumulation of ferrous sulfide (FeS) in macrophages within the lamina propria (Cheng CL, 2000).
Handling and storage
Ferrous Sulfide must be kept away from heat and sources of ignition. Empty containers represent a risk of fire, the residues must be evaporated under an extractor hood. Ground all equipment containing material to avoid electrical sparks.
Dust should not be breathed. Avoid contact with the eyes. Wear suitable protective clothing. In case of insufficient ventilation, wear suitable respiratory equipment.
In case of not feeling well, seek medical attention and display the product label where possible. The compound must be kept away from incompatible substances such as oxidizing agents and acids.
The container containing the compound should be kept dry, in a cool place. And it should be tightly closed in a ventilated place. Combustible materials should be stored away from extreme heat and away from strong oxidizing agents.
Applications
Iron sulfide is used in the alloy and stainless steel industries to control hydrogen embrittlement. The steel industry uses iron sulfide as a resulfurization agent in the manufacture of carbon-free cutting steels, alloy, and stainless steel.
It also acts as a degrading agent to improve the ability of the steel casting machine, which are used in the production of various steel parts. In the purification of crude phosphoric acid, iron sulfide is used as a reducing agent to remove heavy impurities from phosphoric acid.
Another use for iron sulfide is in the production of malleable iron. Iron sulfide combined with ferrous silicon and ferromanganese is used to increase the sulfur content of steel and iron.
Iron sulfide is also used as a laboratory chemical for the preparation of hydrogen sulfide gas. In hair dyes, paint, pottery, bottles, and glasses, iron sulfide is used as a pigment. It is also used in lubricants and to treat exhaust gases.
Iron sulfide has uses that are compatible with sulfates. Sulfate compounds are soluble in water and are used in water treatment. Iron sulfide is also used in the production of metal castings.
Iron sulfide is the mineral pyrite that resembles gold and is dubbed "fool's gold." Pyrite is used in the production of sulfur and sulfuric acid and is also used in coal mining (JAINSON LABS (INDIA), SF).
References
- Cheng CL, ea (2000). Pseudomelanosis duodeni: case report. Changgeng Yi Xue Za Zhi 23 (6), 372-376.
- fisher scientific. (2009, August 20). Material Safety Data Sheet Iron (II) Sulfide. Retrieved from lasecsa.
- JAINSON LABS (INDIA). (SF). Uses of Ferrous Sulphide. Retrieved from jainsonfes.
- Material Safety Data Sheet Ferrous sulfide. (2013, May 21). Retrieved from sciencelab.
- National Center for Biotechnology Information. (SF). PubChem Compound Database; CID = 14828. Retrieved from PubChem.
- (2014, May 15). Preparing Iron (II) Sulfide (cool reaction). Retrieved from youtube.
- Rickard, D. (1995). Kinetics of FeS precipitation: Part 1. Competing reaction mechanisms. Geochimica et Cosmochimica Acta Volume 59, Issue 21, 4367-4379.
- Royal Society of Chemistry. (2015). Iron (II) sulfide. Retrieved from chemspider: chemspider.com.