What is Magnesium Sulphate Heptahydrate / Epsom Salt and what is it used for

Magnesium Sulphate Heptahydrate / Epsom salt

Magnesium sulphate heptahydrate is a white crystalline compound with many applications including in the cosmetics, cleaning, industrial and pharmaceutical areas. Also known as Epsom Salts, it is a type of salt and mineral which is found in the geological environment. This can be obtained from the ore, epsomite, a white solid substance found on the surface of the earth. The chemical is completely soluble in water and consists of three natural elements ie. magnesium, sulphur and oxygen. It is widely used in eliminating skin inflammation of the individuals. Furthermore, the chemical is also used as principal growth stimulators of several plants.

Specification for Magnesium Sulphate BP/USP:

  • Synonyms: Bitter salts; Epsom salt; Magnesium sulfate heptahydrate;
  • Appearance: white crystals
  • Mg SO4.7H2O: 98% minimum
  • MgSO4: 49.1%
  • Water: 50.9%
  • Granulometry <1mm %: Typically 90.0
  • Water insolubles: 0.01 % max
  • Na: 40 mg/Kg
  • K: 130 mg/Kg
  • Ca: 60 mg/Kg
  • Se: 30 mg/Kg max
  • Selenium ppm: 30 max
  • Chloride (as Cl): ppm 90
  • CAS No: 10034–99–8
  • EINECS No: 231–298–2
  • Mol weight: 246.48
  • Melting point: 1124 C
  • Bulk density: 970 g/dm3 approx
  • Density: 2.7 g/cm3
  • Solubility: soluble in water 246 g/l in water at 20C
  • pH: 5.0 – 8.0 at 50 g/L

Uses for Magnesium sulphate / Epsom Salts

Magnesium sulphate is used to maintain the magnesium concentration in marine aquariums which contain large amounts of stony corals as it is slowly depleted in their calcification process. See below – Using Magnesium Sulphate in marine aquariums. Magnesium sulphate is also suggested for dropsy treatment for fish.

Magnesium sulphate is used in manufacture of matches, mineral water, tanning leather and dietary supplements. Other applications include the cotton and silk dyeing industry; increasing the bleaching action of chlorinated lime; manufacture of mother-of-pearl and frosted papers; fire-proofing fabrics; dyeing and printing calicos;

Epsom salts are used in fertilizers for agriculture and gardening. Known for accurate composition, this fertilizer increases the productivity of crop plants and does not affect the fertility of the soil.


Using Magnesium Sulphate in marine aquariums

In an aquarium with low magnesium levels, calcium and alkalinity concentrations are difficult to control because there is a lack of magnesium present to stabilise these ions in the saltwater and prevent their natural precipitation into calcium carbonate.

You should aim to maintain Magnesium levels at around 1300 to 1350ppm using a good quality reliable test kit. 50g (10 teaspoons) will raise Magnesium levels by approximately 50ppm in 100 litres of salt water.

Simply dissolve the required amount into a few litres of Reverse Osmosis Water, mix well and slowly add to your tank in an area of high flow, preferably over a period of an hour or so using a drip line or peristaltic pump. Alternatively add to your evaporation top up water and top up as normal.

It is not recommended to increase Magnesium levels by more than 60ppm per day.

Health & Safety:

Not a hazardous substance or mixture according to Regulation (EC) No. 1272/2008. This substance is not classified as dangerous according to Directive 67/548/EEC.


Where to Buy Magnesium Sulphate GRG Online in the UK



About mistralhowto

formulation chemist

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