Magnesium (Mg) is a highly reactive alkaline earth metal abundant in the Earth’s crust and oceans. This silvery-white metal is fundamental to numerous biological and technological processes, but early scientists only knew it through its compounds. The history of magnesium involves recognizing its unique salts and the eventual isolation of the pure element. Determining when magnesium was discovered requires differentiating between the centuries-long use of its compounds and the moment the pure element was successfully extracted.
Isolating the Element
The formal isolation of the element occurred in 1808. The English chemist Sir Humphry Davy, who had previously used electricity to isolate other metals, was responsible for this breakthrough. Davy employed the technique of electrolysis, passing an electrical current through a mixture of magnesia (magnesium oxide) and mercuric oxide to separate the pure metal.
This success proved that the compounds known for centuries contained a distinct metallic element that could be chemically isolated. Davy initially proposed the name “magnium,” deriving it from the magnesia compound used in his experiment. The pure element was later formalized with the symbol Mg and an atomic number of 12, securing its place in the periodic table.
Compounds Known for Centuries
Long before Davy isolated the metallic element, magnesium-containing substances were widely known and utilized. The most famous compound, magnesium sulfate, became known as Epsom salts after its discovery in 1618 in Epsom, England. It was found when water from a mineral spring yielded a salt upon evaporation that possessed medicinal, laxative effects.
Decades later, in 1755, the Scottish chemist Joseph Black distinguished another magnesium compound, magnesia alba (magnesium carbonate/oxide), from common lime. Black demonstrated that magnesia alba was a separate chemical entity, proposing that it contained a unique earth. However, the technology to extract the pure metallic element from this compound was not yet available.
Why Magnesium Matters Today
Magnesium remains fundamental to both biological life and modern manufacturing. Biologically, magnesium is a cofactor for over 300 enzyme systems in the human body, regulating processes like protein synthesis and energy production. It is also necessary for the proper functioning of nerves and muscles, and much of the body’s magnesium content supports bone health within the skeletal structure.
In the plant kingdom, magnesium is central to the chlorophyll molecule, the pigment responsible for capturing sunlight and enabling photosynthesis. Without magnesium, the chemical reaction converting carbon dioxide into glucose, which forms the base of the food chain, cannot occur.
Magnesium’s industrial applications leverage its physical properties, specifically its low density and reactive nature. The metal is one-third less dense than aluminum, making it highly desirable for lightweight alloys. These alloys are used in the aerospace and automotive industries to improve fuel efficiency. Furthermore, magnesium burns with a brilliant white light, a property exploited since the late 1800s for use in pyrotechnics, flares, and flash photography.