Magnesium is a light, silvery-white element abundant in the Earth’s crust and oceans, playing a part in numerous natural processes. It is a fundamental component for various biological functions, including its role in chlorophyll and photosynthesis. This versatile element finds extensive use across different industries.
The Road to Recognition
Compounds containing magnesium were known and utilized for centuries before the element itself was isolated. A notable example is “magnesia alba,” a white powder derived from magnesium carbonate, which gained recognition for its medicinal properties. In 1754, Scottish chemist Joseph Black made a significant advancement by distinguishing magnesia alba from lime (calcium carbonate). Black’s experiments demonstrated that magnesia alba, when heated, released a gas he termed “fixed air” (carbon dioxide), leaving behind a lighter residue he called calcined magnesia (magnesium oxide).
His work established that magnesia alba was a distinct substance, not merely a form of lime, and suggested it contained a unique elemental component. Black’s findings were presented in his 1755 paper, “Experiments upon Magnesia Alba, Quicklime, and Some Other Alcaline Substances,” which also highlighted its use as an antacid. This conceptual groundwork was further advanced by French chemist Antoine Lavoisier, who, in his 1789 classification of elements, included “earths” like magnesia as potential elemental substances. Lavoisier’s categorization, based on observable properties, paved the way for future chemists to pursue the isolation of these suspected elements.
The Definitive Isolation
The isolation of pure metallic magnesium was achieved by Sir Humphry Davy in 1808. Davy, a British chemist, successfully obtained small quantities of magnesium through the process of electrolysis.
Specifically, Davy employed electrolysis on a paste of moist magnesia (magnesium oxide) and red mercury oxide, using mercury as the negative electrode. This process resulted in the formation of a magnesium-mercury amalgam. By then heating this amalgam, Davy was able to distill off the mercury, leaving behind impure metallic magnesium. His work, announced in a lecture to the Royal Society in June 1808, marked the first successful isolation of the element in its metallic form.
Early Scientific Insights
Following its isolation, Davy and other early chemists began to observe the initial properties of magnesium. Davy noted that the newly isolated metal would quickly turn into a white powder when exposed to air, indicating its reaction with oxygen to revert to its oxide form.
Obtaining pure magnesium in substantial quantities remained challenging and costly, hindering widespread practical applications immediately after its discovery. Magnesium was recognized as an alkaline earth metal, sharing chemical similarities with calcium and strontium. Its classification alongside these elements was based on its chemical behavior, as chemists refined production techniques and explored its characteristics.