Magnesium Sulfate (Epsom Salt)
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Magnesium sulfate (or sulphate) is a chemical compound containing magnesium, with the formula MgSO4. It is often encountered as the heptahydrate, MgSO4·7H2O, commonly called Epsom salts. Anhydrous magnesium sulfate is used as a drying agent. Since the anhydrous form is deliquescent and therefore harder to weigh accurately, the hydrate is often preferred when preparing solutions, for example in medical preparations. Epsom salts have traditionally been used as a component of bath salts.
In agriculture and gardening, magnesium sulfate is used to correct magnesium deficiency in soil (magnesium is an essential element in the chlorophyll molecule). It is most commonly applied to potted plants, or to magnesium-hungry crops, such as potatoes, roses, and tomatoes. The advantage of magnesium sulfate over other magnesium soil amendments (such as dolomitic lime) is its high solubility.
Use in organic chemistry
Anhydrous magnesium sulfate is commonly used as a desiccant in organic synthesis due to its affinity for water. During workup, an organic phase is saturated with magnesium sulfate until it no longer forms clumps. The hydrated solid is then removed with filtration or decantation.
A number of other inorganic sulfate salts, sodium sulfate and calcium sulfate for example, may also be used in the same way.
Magnesium sulfate is used as in bath salts, particularly in flotation therapy where high concentrations raise the bath water’s specific gravity, effectively making the body more buoyant. This property is also used to restore some Lava lamps damaged by being shaken by exchanging the water and adding drops of a concentrated solution until sustainable buoyancy is reached. Traditionally, it is also used to prepare foot baths, intended to soothe sore feet. The reason for the inclusion of the salt is cosmetic: the increase in ionic strength prevents some of the temporary skin wrinkling (“pruning”) which is caused by prolonged immersion of extremities in pure water. Magnesium sulfate paste has been used as an agent for drawing (dehydrating) boils and carbuncles. It is an ingredient in Diet Coke Plus.
It is also recommended for dropsy treatment for fishes.