Magnesium Sulphate -MgSO₄

Magnesium sulphate is a salt of magnesium with sulphuric acid. It is an anhydrous inorganic salt. However its anhydrous form is quite unstable so this salt exists as its hydrate salt with common formula \[ MgSO_{4}.nH_{2}O \] where it can have different values like 1,2,3...7.. etc. The most common hydrate salt of Magnesium sulphate is the Magnesium sulphate heptahydrate which has 7 molecules of water and has a formula \[ MgSO_{4}.7H_{2}O \]. This salt is also known as Epsom salt.

Structure of \[MgSO_{4}\] Molecules

Magnesium sulphate is an ionic salt. It is formed when an ionic bond is formed between magnesium ion \[Mg^{+2}\] and sulphate ion \[SO{_{4}}^{-2}\].  There is an electrostatic force of attraction between the positive magnesium ion and the negative sulphate ion. The structure of sulphate ion consists of 2 oxygen atoms doubly bonded to the sulphur atom and 2 oxygen atoms singly bonded to the same sulphur atom. 

Magnesium Sulphate Chemical Formula

The chemical formula of Magnesium sulphate is \[MgSO_{4}\]. This formula is obtained by crisscrossing the valency of the magnesium and sulphate ions. Both have the same valency, therefore, it gets cancelled and one is obtained. 

Certain Facts about Magnesium Sulphate

• Magnesium sulphate heptahydrate is also known as Epsom salt.

• In medicine,  doses of magnesium sulphate can be administered orally or intravenously. 

• Anhydrous magnesium sulphate is used as a desiccant.

• Magnesium sulphate is also known as the sulphuric acid magnesium salt.

• Magnesium sulphate is believed to prevent labour pains in pregnant women. 

• Eclampsia is a condition of pregnant women where seizures occur during or after childbirth. Magnesium sulphate is believed to control eclampsia in pregnant women. However, this condition is rare and its cases are less than 1 million per year in India.

• In pregnant women, it is used to control seizures. However, it's not considered safe to administer magnesium sulphate doses during pregnancy. 

• In the preparation of tofu, coagulants are required. Magnesium sulphate is used as a coagulant in tofu making.

• Magnesium sulphate hydrate salts are used to form various double salts. Potassium magnesium sulphate and sodium magnesium sulphate are some of the double salts that include magnesium sulphate as their components.

• In making beer magnesium sulphate salt is used as a brewing salt.

Properties of Magnesium Sulphate \[MgSO_{4}\]

Physical properties of magnesium sulphate are-

• Its hydrate forms are crystalline solids and are white. Magnesium sulphate is an anhydrous solid salt of white colour.

• It is an odourless salt.

• Magnesium sulphate salt is soluble in water. It's interesting to note that the solubility of magnesium sulphate increases with an increase in temperature.

• Magnesium sulphate is not soluble in organic solvents like alcohol.

• The density of anhydrous magnesium sulphate is 2.66g/cm3.

• The molecular weight of magnesium sulphate is 120.366 g/mol.

• Magnesium sulphate is not tasteless. Rather it has a bitter taste and saline taste.

• The melting point of this salt is very high and is around 1120 degrees Celsius.

Adverse Effects of Magnesium Sulphate on Humans.

• If higher doses of magnesium sulphate are taken then it can be life-threatening. Doses greater than recommended by the doctor if taken can prove lethal.

• Excessive consumption of magnesium sulphate leads to a condition hypermagnesemia, which refers to the excess of magnesium ions in the blood. This excess magnesium interferes with the normal functions of the body. 

What is Magnesium Sulphate used for?

External Uses

• Isolation Tanks- In flotation treatment, magnesium sulphate is widely used to generate the concentrated solutions that fill the isolation tanks.

• Mineral Waters- Some mineral waters naturally include magnesium and sulphate ions.

• Bath Salts- Magnesium sulphate is used in bath salts, particularly for foot baths, to relieve aching feet. The salt is included for cosmetic reasons: the increased ionic strength reduces some of the transient skin wrinkling (partial maceration) that would occur with plain water bathing.

• Drawing Paste- In the United Kingdom, a medicine containing magnesium sulphate known as "drawing paste" is reported to be effective for treating minor boils or localised infections as well as removing splinters.

Internal Uses

• Magnesium Deficiency- Magnesium sulphate is used as a magnesium replacement treatment.

• Asthma- After beta-agonist and anticholinergic drugs have been tried, magnesium sulphate may be utilized as a bronchodilator, for example, in severe asthma exacerbations.

• Arrhythmia- According to the ECC recommendations, magnesium sulphate may be used as an antiarrhythmic medication for torsades de pointes in cardiac arrest and the management of quinidine-induced arrhythmias.

• Early Delivery- Magnesium sulphate appears to reduce the incidence of cerebral palsy in women at risk of premature birth.

• Eclampsia- Magnesium sulphate has been shown to reduce the incidence of preeclampsia progressing to eclampsia. Intravenous magnesium sulphate is used to prevent and treat eclampsia seizures.

Cautions Before taking Magnesium Sulphate as Medicine

If you have any of the following conditions, do not take magnesium sulphate as a laxative without first consulting your doctor:

• severe stomach pain;

• nausea or vomiting;

• a perforated bowel;

• bowel obstruction or severe constipation;

• colitis or toxic megacolon; or

• a sudden change in bowel habits lasting 2 weeks or longer.

If you have any of these symptoms, see a doctor or pharmacist to be assured if taking this drug is safe for you.

• diabetes;

• kidney disease;

• an eating disorder (anorexia or bulimia);

• if you have already been using a laxative for longer than 1 week; or

• if you are on a low-magnesium diet.