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magnesium sulfate[mag′nē·zē·əm ′səl‚fāt]
MgSO4, a salt; colorless crystals. Density, 2.66 g/cm3. Decomposes into MgO, SO2, and O2 at 1100°-1200°C.
Solubility in water, 25.2 percent (by weight) at 20°C. It forms crystalline hydrates with one, two, three, four, five, six, seven, and 12 water molecules; the crystallization of MgSO4.7H2O from aqueous solutions takes place at room temperature. Magnesium sulfate occurs naturally as kieserite, MgSO4.H2O, and epsomite MgSO4«7H2O (Epsom salt). It interacts with salts of alkali metals to form double salts, among them langbeinite, K2SO4.2MgSO4; astrakanite, Na2SO4.MgSO4.4H2O; polyhalite, K2SO4.MgSO4.2CaSO4.2H2O; and kainite, KCL MgSO4.3H2O (all of which occur in nature).
Magnesium sulfate is extracted from natural ocean brines and solid salt deposits. It is used to prepare SO2 in the production of H2SO4, and also in the manufacture of magnesia cement, in the textile industry as a filler and mordant, in the paper industry as a filler, and in agriculture.
In medicine, magnesium sulfate serves as a tranquilizer, antispasmodic, laxative, and cholagogue. It is available in prepared solution (for intramuscular or intravenous injection) or in powder form.