Magnesium Sulphate

Commonly known as "epsom salt", it is traditionally used as a beauty product. Athletes use it to soothe sore muscles, while gardeners use it to improve crops. It has a variety of other uses covering several industries.

Synonyms: Bath salt, Bitter salt, English salt, Epsom salt, MAG
Chemical Formula: MgSO4; MgSO4.7H20
CAS Number: 7487-88-9 (anhydrous), 10034-99-8 (heptahydrate)

Characteristics

Molar Weight: 120.34 g/mol (anhydrous), 246.47 g/mol (heptahydrate)

Melting Point: 1124°C (anhydrous, decomposes), 150°C (heptahydrate, decomposes)

Density: 2.66 g/cm3 (anhydrous), 1.68 g/cm3 (heptahydrate)

Forms: Powder, White, Odorless

Uses and applications

Key applications

Fertiliser
Agricultural
Pharmaceuticals

Industries

General information about Magnesium Sulphate

Magnesium sulphate is one of the two magnesium salts of sulphuric acid, the other being magnesium hydrogen sulphate. It is a widely occurring natural mineral found both on Earth and on other celestial bodies, such as Mars.

Magnesium sulphate exists in various forms. Of particular relevance is the mineral epsomite, the most common natural form, also known as Epsom salt. Epsomite corresponds to magnesium sulphate heptahydrate (MgSO4.7H2O) and is formed by evaporation in saline environments, such as salt lakes or as efflorescence in dry areas. The name Epsom salt comes from the English town of Epsom, where it was once extracted from natural sources.

The magnesium sulphate monohydrate kieserite (MgSO4.H2O) is a form with less water content and is found in salt deposits. It serves as an important raw material for the industrial production of magnesium sulphate.

In addition to the various hydrated forms, magnesium sulphate is also found in dissolved form in seawater. It contributes to the overall minerality of the ocean and is a component of the salts that remain after seawater evaporates.

Natural deposits of epsomite and kieserite are mined worldwide, especially in regions with large salt deposits such as Germany, Russia, Canada and the USA (including Great Salt Lake).

Properties of magnesium sulphate

Magnesium sulphate is a colourless and odourless solid with a bitter taste. It is highly soluble in water and strongly hygroscopic. Heptahydrate (MgSO4.7H2O), which occurs most frequently in nature, is particularly relevant.

Industrial production involves the reaction of magnesium oxide, magnesium hydroxide or magnesium carbonate with sulphuric acid (H2SO4). Extraction from natural deposits is also common.

Magnesium sulphate in agriculture

In agriculture, magnesium sulphate is used as a fertiliser and soil improver. It provides plants with essential nutrients – magnesium for chlorophyll formation and sulphur for protein metabolism. Crops such as potatoes, tomatoes, peppers and citrus fruits benefit particularly from this.

In animal nutrition, magnesium sulphate serves as a source of magnesium. A deficiency can lead to muscle tremors, cramps, nervousness and, in extreme cases, pasture tetany (grass sickness) in animals – an often fatal disease in ruminants such as cows and sheep.

Magnesium sulphate in the pharmaceutical industry

In the pharmaceutical industry, magnesium sulphate is a versatile active ingredient and excipient in medical applications:

Under the name Epsom salt, it is used as an osmotic laxative
It is used to treat pre-eclampsia and eclampsia during pregnancy
In emergency medicine, it is used to treat cramps, tetanus, cardiac arrhythmia and, in severe cases, asthma, as it relaxes the smooth muscles of the respiratory tract
As a source of magnesium, it is administered for hypomagnesaemia and muscle cramps

In addition, magnesium sulphate is used in therapeutic baths to relieve muscle pain, inhibit inflammation and treat skin conditions such as psoriasis, eczema and acne. It also serves as a filler and carrier material as an excipient in drug production.

Magnesium sulphate in the food industry

Magnesium sulphate is approved for use in food production under E number E 518, where it fulfils the following functions, among others:

Source of magnesium: additive in beverages (e.g. juices, milk alternatives, energy drinks) and muesli mixes
Firming agent: Stabilisation of the cell structure in canned fruit and vegetables
Acidity regulator and emulsifier: Regulation of the pH value and improvement of the fat-water emulsion, e.g. in sauces or dressings
Coagulant: In tofu production, magnesium sulphate serves as a coagulant to solidify soy milk.
Technical aid: Carrier for flavours, vitamins and colourings, as well as an auxiliary in the manufacture of powdered products.

It is also used in beer production to optimise yeast activity and flavour balance.

Magnesium sulphate in the cosmetics industry

Magnesium sulphate is used in numerous cosmetic products by the cosmetics industry, particularly because of its moisture-binding, nourishing and skin-soothing properties. Typical areas of application are:

Skin care: Ingredient in creams, lotions and serums for dry or irritated skin
Exfoliants: As an abrasive (Epsom salt) to remove dead skin cells
Bath salts: Promote muscle relaxation and soothe irritated skin
Hair care: Adds volume, regulates oil content and improves texture
Make-up: Ingredient in primers, powders and foundations for a mattifying effect.

Magnesium sulphate also acts as a stabiliser and texturiser in cosmetic formulations.

Magnesium sulphate in water treatment

Magnesium sulphate is used in a variety of ways in water treatment.

Drinking water: Regulation of mineral content and regeneration of ion exchangers
Wastewater treatment: Stabilisation of the micronutrient balance in biological sewage treatment plants; removal of phosphates
Corrosion protection: Regulation of alkalinity and stabilisation of water quality in industrial systems
Aquaculture: Improvement of water quality and mineral balance.

Magnesium sulphate in the construction industry

Magnesium sulphate is a component of numerous products in building materials technology.

Cement production: Formation of magnesium sulphate cement (Sorel cement), which impresses with its high strength, chemical resistance and low shrinkage
Magnesia boards: Component of magnesium oxide boards, which are versatile due to their fire and moisture resistance (walls, ceilings, floors)
Concrete additive: Improves durability and consistency
Refractory materials: Component of casting moulds and insulating materials, especially for the steel and glass industries
Construction chemicals: Used in plasters, adhesives and sealants to improve adhesion and chemical stability.

Magnesium sulphate in the lubricant industry

In lubricant technology, magnesium sulphate is mainly used as a desiccant to remove moisture, acids or impurities from oils and greases.

It stabilises additive systems, prevents the precipitation of ingredients and contributes to the homogeneity of lubricant mixtures.

It also regulates the pH value and improves the consistency of lubricating greases and emulsions.

Magnesium sulphate in the rubber and caoutchouc industry

Magnesium sulphate is used as an auxiliary material in rubber and caoutchouc processing.

During the vulcanisation of raw caoutchouc into elastic rubber, it improves the physical properties – in particular hardness, elasticity and heat resistance.

It also acts as a drying agent and moisture regulator, prevents blistering and improves the thermal stability and homogeneity of rubber compounds.

Typical end products are:

Car tyres
Conveyor belts
Shoe soles
Rubber hoses
Seals and covers

Summary

Magnesium sulphate is a versatile raw material that plays an essential role in numerous industries. From agriculture to the pharmaceutical, food and cosmetics industries to construction, water and rubber technology, it impresses with its chemical stability, reactivity and functionality. Its wide range of applications makes magnesium sulphate an indispensable component of modern industrial processes.