Medical Magnesium sulfate is used both externally (as Epsom salt) and internally. The main external use is the formulation as
bath salts, especially for
foot baths to soothe sore feet. Such baths have been claimed to also soothe and hasten recovery from muscle pain, soreness, or injury. Health effects of magnesium sulfate that have been proposed include improvement of treatment resistant depression and as an
analgesic for
migraine and
chronic pain. Magnesium sulfate is usually the main component of the concentrated salt solution used in
isolation tanks to increase its
specific gravity to approximately . This high density allows an individual to float effortlessly on the surface of water in the closed tank, eliminating stimulation of as many of the external senses as possible. In the
UK, a medication containing magnesium sulfate and
phenol, called "drawing paste", is useful for small boils or localized infections and removing splinters. Internally, magnesium sulfate may be administered by oral, respiratory, or
intravenous routes. Internal uses include replacement therapy for
magnesium deficiency, treatment of acute and severe
arrhythmias, preventing
eclampsia and
cerebral palsy, a
tocolytic agent, It also may be used as
laxative.
Agriculture In
agriculture, magnesium sulfate is used to increase magnesium or sulfur content in soil. It is most commonly applied to potted plants, or to magnesium-hungry crops such as potatoes, tomatoes, carrots, peppers, lemons, and roses. The advantage of magnesium sulfate over other magnesium
soil amendments (such as
dolomitic lime) is its high solubility, which also allows the option of
foliar feeding. Solutions of magnesium sulfate are also nearly pH neutral, compared with the
slightly alkaline salts of magnesium as found in
limestone; therefore, the use of magnesium sulfate as a magnesium source for soil does not significantly change the
soil pH. Magnesium sulfate was historically used as a treatment for
lead poisoning prior to the development of
chelation therapy, as it was hoped that any lead ingested would be precipitated out by the magnesium sulfate and subsequently purged from the
digestive system. This application saw particularly widespread use among veterinarians during the early-to-mid 20th century; Epsom salt was already available on many farms for agricultural use, and it was often prescribed in the treatment of farm animals that had inadvertently ingested lead.
Food preparation Magnesium sulfate is used as: •
Brewing salt in making
beer •
Coagulant for making
tofu • A
food additive to add taste to bottled water.
Chemistry Anhydrous magnesium sulfate is commonly used as a
desiccant in
organic synthesis owing to its affinity for water and compatibility with most organic compounds. During
work-up, an organic phase is treated with anhydrous magnesium sulfate. The hydrated solid is then removed by
filtration,
decantation, or by
distillation (if the boiling point is low enough). Other inorganic sulfate salts such as sodium sulfate and
calcium sulfate may be used in the same way.
Hydrates Magnesium sulfate can
crystallize as several
hydrates, including: • Anhydrous, ; unstable in nature, hydrates to form
epsomite. • Monohydrate, ;
kieserite,
monoclinic. Further heating to gives anhydrous magnesium sulfate.
Undecahydrate The undecahydrate ,
meridianiite, is stable at
atmospheric pressure only below . Above that temperature, it liquefies into a mix of solid heptahydrate and a
saturated solution. It has a
eutectic point with water at and 17.3% (mass) of . This cement is mainly used in the production of lightweight insulation panels, although its poor water resistance limits its usage. Magnesium (or sodium) sulfate is also used for testing
aggregates for soundness in accordance with
ASTM C88 standard, when there are no service records of the material exposed to actual
weathering conditions. The test is accomplished by repeated immersion in saturated solutions followed by oven drying to dehydrate the salt precipitated in permeable
pore spaces. The internal expansive force, derived from the rehydration of the salt upon re-immersion, simulates the expansion of water on freezing. Magnesium sulfate is also used to test the resistance of concrete to external
sulfate attack (ESA).
Aquaria Magnesium sulfate heptahydrate is also used to maintain the magnesium concentration in marine aquaria which contain large amounts of
stony corals, as it is slowly depleted in their
calcification process. In a magnesium-deficient marine aquarium, calcium and
alkalinity concentrations are difficult to control because not enough magnesium is present to stabilize these ions in the saltwater and prevent their spontaneous
precipitation into
calcium carbonate. ==Double salts==