How To Make Magnesium Chloride

Magnesium chloride officially refers only to the compound MgCl2, although in common usage the term \"magnesium chloride\" applies to the hydrates of magnesium chloride MgCl2(H2O)x as well. It's an ingredient in a variety of commercial products such as cement, paper and textiles, and is also used as a dietary supplement and de-icing agent. Magnesium chloride is mined from sea beds, and hydrated magnesium chloride is extracted from sea water.

Step 1

Extract magnesium hydroxide from sea water. Add slaked lime (CA(OH2)) to sea water to the magnesium (Mg2+) ions to fall out of the solution as the precipitate magnesium hydroxide. The following equation shows this reaction: Mg2 + Ca(OH)2 ? Mg(OH)2 + Ca2+.

Step 2

Convert the magnesium hydroxide obtained in Step 1 to magnesium chloride hydrates with hydrochloric acid (HCl). The following equation shows this reaction: Mg(OH)2 + 2 HCl ? MgCl2 + 2 H2O. This reaction is known as the \"Dow Process\" and is used on a commercial scale.

Step 3

Use HCl to convert magnesium carbonate (MgCO3) into MgCl. This method is useful because MgCO3 is a mineral that occurs in commercially useful quantities. The following equation shows this reaction: Mg(CO)3 + 2 HCl ? MgCl2 + CO2 + H20.

Step 4

Make MgCl in the laboratory from Mg and HCl as follows: Mg + 2 HCl ? MgCl2 + H2. This reaction is a common laboratory experiment, but is far too inefficient to be commercially practical.

Step 5

Prepare MgCl2 from magnesium sulfate (MgSO4) and table salt (NaCl). Heating a concentrated solution of these reagents and then cooling it rapidly will cause the following reaction to occur: MgSO4 + 2 NaCl ? MgCl2 + Na2S04.