How to Extract Magnesium Chloride From Sea Salt
Magnesium (Mg) exists in sea water as ions of magnesium. It's typically extracted from sea water on an industrial scale in a procedure known as the Dow Process. Magnesium chloride is used in the manufacture of fire-resistant materials, paper and textiles. It's also a common deicing agent and a precursor in the production of magnesium metal.
Instructions
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Add slaked lime [Ca(OH2)] to sea water. The magnesium ions (Mg) in the sea water will combine with the slaked lime to form magnesium hydroxide [Mg(OH)2] and calcium. Magnesium hydroxide is a solid that will fall to the bottom of the solution as a precipitate and the calcium will remain in the solution as ions. The following equation shows this reaction: Mg + Ca(OH)2 ' Mg(OH)2 + Ca.
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2
Separate the magnesium hydroxide from the sea water and add two moles of hydrochloric acid (HCl) for every mole of magnesium hydroxide. This reaction will form a solution of magnesium chloride in water. The following equation shows this reaction: Mg(OH)2 + 2 HCl ' MgCl2 + 2 H2O.
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3
Add four moles of water to the magnesium chloride solution for every mole of magnesium chloride. The following equation shows this reaction: MgCl2 + 2 H2O + 4 H20 ' MgCl2 + 6H20.
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Allow this solution to crystallize as magnesium chloride hexahydrate (MgCl2.6H20).
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5
Store magnesium chloride as magnesium chloride hexahydrate. Pure magnesium chloride is difficult to store because it absorbs water extremely readily. Magnesium chloride hexahydrate may be dehydrated to magnesium chloride when needed by exposing it to hydrogen chloride gas.
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