Magnesium—-a Metal in Flash Lamp


When photographers take pictures for a grand assembly at night, there is often with the sound of “click” and dazzling flash. This flash is what magnesium powder gives out when it burns in air.

Magnesium was first discovered by a British chemist David in 1808 via the electrolysis process. The original intent of its Greek name means “magnesia”, because one of magnesium ores named magnesia was in rich in Magnesia of Greece. In the nature, magnesium is one of widespread elements. In the earth’s crust, magnesium content is about fourteen thousandths. The main magnesium ores are magnesium dolomite and magnesite, etc. There is magnesium existing in asbestos, talc, sepiolite. Especially in seawater, magnesium content ranks only second to sodium. Magnesium, a silvery-white light metal, is very similar to aluminum but lighter than aluminum, with weight of 1.74 tons per cubic meter, only two-thirds of the same volume of aluminum. Magnesium is very hard, with good mechanical properties.

Like aluminum, magnesium’s surface will be rapidly oxidized and lose luster in air, while it will simultaneously generate a thin layer of oxide film, which is so stable that it can protect and prevent the oxidization of inside metal again. Magnesium gives off a dazzling light when burns in air. The white light will be brighter if it burns in pure oxygen. Therefore, magnesium metal powder is made into flash powder (a mixture of magnesium and potassium chlorate) for the photography at night. In addition, magnesium powder is also made into flares and fireworks, etc.

However, the most important use of magnesium is used to make alloys. Magnesium-aluminum alloy is the most common magnesium alloy, with magnesium of 5-30%. With greater strength, magnesium-aluminum alloy is harder than pure aluminum, and easier to process and polish than aluminum. And it is exceptionally lightweight and used in aircraft manufacturing in large quantity, to be an important “Defense Metals”. Besides, it is also used in the manufacture of automobiles and other vehicles. According to foreign reports, magnesium alloy for the structure in 1972 had a substantial increase over 1971. A new magnesium alloy with yttrium of 9% and zinc of 1% is light and strong for the manufacture of helicopter parts. In addition, adding 0.05% of magnesium in cast iron can greatly increase the ductility and crack resistance.

Magnesium oxide and magnesium sulfate are the most important magnesium compounds. Magnesium oxide is a good refractory material with a very high melting point up to 2,800°C. The “magnesium brick” used for blast furnace contains a large amount of magnesium oxide, which can withstand temperatures above 2,000°C. Magnesium oxide is also used to produce cement which is not only superior building materials but also commonly used to make grindstones and grinding wheels. If wood shavings are soaked in magnesia cement paste via pressure, they will become sturdy and durable fiberboards after the hardening. Such fiberboard not only is very light and fire-resistant, but also is good at heat insulation and sound insulation.

Magnesium sulfate is known as a laxative, which is a colorless crystalline substance and easily soluble in water with a bitter taste. It is difficult to be absorbed by the intestine when patients take it orally, but the osmotic pressure will lead to a lot of water leave in the intestines so as to increase intestinal volume and mechanically stimulate the muscle wall, thus causing the defecation. Taking magnesium sulfate is relatively safe, but the dose must be controlled within some limits, about 15-30g each time for adults. Magnesium sulfate is also used in the textile industry and paper industry.

Magnesium is extremely important in biology, because it is the core atom of the chlorophyll molecule which is constituted by the magnesium atom surrounded by a lot of hydrogen atom and oxygen atom, with magnesium content of 2% in chlorophyll. Without magnesium, there is no chlorophyll, no green plants, no food and vegetables. It is estimated that magnesium content is up to l00 tons in plants all over the world. Applying magnesium fertilizer to soil can significantly improve the yield, especially for beets.