Magnesium sulfate crystals can be prepared from Epsom salt available in pharmacies. Natural magnesium sulfate exists as the mineral kieserite, MgSO4?H2O, which is purified by crystallization.
Boil water, and add Epsom salt after removing the water from the heat. The Epsom salt totally dissolves in the water, and food coloring can be added to the solution. Pour the entire mixture onto a sponge or into an empty container. When the container is kept in the hot sun, the water evaporates, leaving behind the magnesium sulfate crystals. The formation of crystals takes place more quickly and is easier to view and handle on the sponge. The Epsom salt that was initially dissolved in water differs in its appearance from the crystals that are prepared. The crystals are centrifuged, dried and sieved for industrial applications.
Magnesium sulfate can also be prepared from magnesium oxide and magnesium carbonate by their reaction with sulfuric acid. The procedure for this preparation involves the addition of a small amount of magnesium carbonate into 20 milliliters of sulfuric acid, slowly added into the acid. After dissolving the solid in the mixture thoroughly, the solution is filtered and evaporated. The crystals are formed by heating the solution on a Bunsen burner, and then they are cooled.