Adam McCormack, age 14, of Nogales, Ariz., for his question:
WHERE DO WE FIND MAGNESIUM?
Magnesium is a silver gray metal. It cannot be found in nature in its pure form, however. But compounds of magnesium, that is, magnesium mixed with other chemical elements, make up more than 2 percent of the rocks of the earth's crust. Today in the United States, all metallic magnesium is taken out of sea water.
Magnesium is lighter and stronger than aluminum. Most magnesium is used to make light alloys, or mixtures of metals. Alloys of magnesium are used in the manufacture of airplanes, cars, trucks, boats and jet engines.
We've known about magnesium for years. In the late 1600s, an English doctor named Nehemiah Grew found a mineral salt while experimenting in the waters of Epsom. The salt, magnesium sulfate, became known as Epsom salt.
Another magnesium mineral, this one called magnesia, was found in 1808 by an English chemist named Sir Humphrey Davy. It was a compound of magnesium oxide, but Davy couldn't separate it to fine pure magnesium.
Most magnesium comes from three mineral sources: carnallite (a chloride of potassium and magnesium), kieserite (a sulfate of magnesium) and magnesite (a carbonate of magnesium).
A cubic yard of sea water contains almost a pound and a half of magnesium while a cubic mile will have about 4 million tons of magnesium. Sea water is rich in magnesium because through the centuries, rivers and streams have carried much of the dissolved element from the continents.
Electrolysis is the most common way of separating magnesium from its compounds. Melted magnesium chloride is mixed with other substances that lower the melting point and increase the material's electrical conductivity.
The molten salts are put into large cast iron or steel pots with graphite bars hung in them. The graphite bars are charged positively while the pots are charged negatively. As the current passes through the salt bath, molten magnesium is formed near the surface and is drawn off.
Another method of separating magnesium from its compounds uses electrolysis and high temperature. Gases or vapors of magnesium and other substances are released from the molten material. The pure magnesium metal is than condensed from the vapor.
Magnesium alloys, or mixtures of metals, are used widely in industries because the finished product is strong and hard. Also, alloys do not corrode as easily as pure magnesium.
Magnalium and Duralumfn are alloys of aluminum and magnesium.
In addition to carnallite, magnesite and the salts of the sea, magnesium is found in many minerals and in many useful chemical combinations. These include dolomite, asbestos, soapstone, meerschaum, serpentine and bruxite. Chlorophyll, the green coloring substance you find in plants, also contains magnesium.