Discovery of Calcium

People have used calcium’s compounds for thousands of years – in cement, for example.

Limestone [calcium carbonate] was called calx by the Romans. The Romans heated calx, driving off carbon dioxide to leave calcium oxide. To make cement, all you have to do is mix calcium oxide with water. The Romans built vast amphitheaters and aqueducts using calcium oxide cement to bond stones together.

Despite the long history of calcium’s compounds, the element itself was not discovered until electricity was available for use in experiments.

Calcium was first isolated by Sir Humphry Davy in 1808 in London. In a lecture to the Royal Society in June 1808, Davy described his experiments that year, which produced tiny amounts of metal, at best. He could not find any way to produce more calcium metal until a letter from Jöns Berzelius in Stockholm pointed him in the right direction.

Davy learned that Berzelius and Magnus Pontin had used a battery to decompose calcium oxide at a mercury electrode and they had obtained an amalgam of mercury and calcium. (Berzelius, the great Swedish chemist, exchanged a great deal of information with Davy. Berzelius had earlier learned from Davy that potassium could be dissolved in mercury to form an amalgam. Berzelius had extended the method.)

Davy made a paste of slaked lime [calcium oxide, slightly moistened to form calcium hydroxide] and red oxide ofmercury [mercury (II) oxide]. 

He made a depression in the paste and placed about 3.5 grams of mercury metal there to act as an electrode. Platinum was used as the counter electrode. Davy carried out the experiment under naptha (a liquid hydrocarbon under which he had found he could safely store potassium and sodium).

When electricity was passed through the paste, a calcium-mercury amalgam formed at the mercury electrode.

Davy removed the mercury by distillation to reveal a new element: calcium.

Davy used the same procedure to isolate strontium,barium, and magnesium.

He named the metal calcium because of its occurrence in calx.

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