Share facts or photos of intriguing scientific phenomena.

Properties of Magnesium Sulfate

Properties of Magnesium Sulfate

Magnesium sulfate is an essential mineral in various ways, because of its numerous properties and uses. The following article provides brief information regarding the physical and chemical properties of this mineral.
Bidisha Mukherjee
Last Updated: Jun 3, 2018
Magnesium sulfate is a compound with many properties and uses. It is a type of mineral salt, which is widely found in the geological environment. It is obtained from the ore called Epsomite, which is a white solid substance found on the Earth's surface. Besides this, it is also found in oceans and natural springs. This chemical compound formed by magnesium and sulfate is represented by the molecular formula MgSO4. Thus, the magnesium sulfate chemical structure consists of a cation of magnesium (Mg) bonded with four anions of sulfate (SO4).

Commercially, it is produced by dissolving magnesium carbonate in hot and dilute sulfuric acid. The product that is obtained is magnesium sulfate heptahydrate (MgSO4.7H2O). The prefix 'hepta' refers to the seven molecules of water, which are loosely bound to each of the magnesium sulfate molecules. This product is also commonly known as Epsom salt.


Physical Properties of Magnesium Sulfate
  • Physical State: Magnesium sulfate is a colorless and odorless substance with fine needle-like structures.
  • Taste: It is slightly bitter in taste.
  • Solubility: It is highly soluble in inorganic solvents like water. At room temperature, around 700 grams of magnesium gets dissolved in one liter of water. It is partially soluble in organic solvents like glycerin and alcohol.
  • Hygroscopy: Magnesium sulfate in its anhydrous form is hygroscopic. It has a tendency to easily attract moisture from the air. Due to this property, it is often used as a drying agent in organic synthesis.
  • Sound Absorption: This salt has the ability to convert acoustic energy into heat energy. In sea water, magnesium is mainly responsible for the absorption of sound. It mainly affects sound of higher frequencies.
Chemical Properties of Magnesium Sulfate
  • Hydrates: Magnesium is found in various types of hydrates, other than heptahydrate. It also forms hexahydrate (6), pentahydrate (5), starkeyite (4), and sanderite (2). But the occurrence of these types are rare. Kieserite is the monhydrate form, which is obtained in evaporitic deposits of seawater.
  • pH Scale: Magnesium sulfate solution is neither acidic nor basic. The pH of magnesium sulfate is 6.0 on the standard pH scale.
  • On heating: When heated at 250ยบ C, heptahydrate loses water to form anhydrous salt. On further heating, the salt is partially broken down to magnesium oxide.
  • Reaction with Water: Is magnesium sulfate soluble in water? When dissolved in water, magnesium sulfate splits into ions of magnesium and sulfate.
Medicinal Benefits

Magnesium sulfate also has some therapeutic properties. Due to its cathartic characteristics, it can be used when needed as a laxative to evacuate the bowel. Applying magnesium paste on boils help in the drainage and healing of boils. In flotation therapy, magnesium sulfate is used as a bath salt. Here, the high concentration of salt raises the specific gravity of bath water, which makes the body buoyant, and helps it to relax.

Magnesium sulfate has huge demand in various industries because of its versatility. Some of its key uses are: as a protein coagulant for food products, leather tanning agent in leather industry, fireproof agent, dyeing agent, salt agent, and plastic stabilizers.