Calcium

Calcium has been part of human history for thousands of years. As far back as 7000 BCE, ancient civilizations were using lime (calcium oxide, CaO) as a building material and a plaster for statues. The Romans were especially known for using lime in their cement, concrete, and mortar, calling it calx. But while they used calcium in all sorts of ways, the element itself wasn’t discovered until much later.

It wasn’t until 1789 that French chemist Antoine Lavoisier figured out that lime contained a new element. Lavoisier was a pioneer in chemistry, and he was the first to suggest that calcium was hiding inside lime as part of an oxide (an element combined with oxygen).

In 1808, British chemist Sir Humphry Davy took on the challenge of isolating calcium. Using a method called electrolysis, which involves using electricity to break down substances, Davy was able to separate calcium from the calcium oxide. This wasn’t easy though! He had to build on earlier experiments done by Swedish chemists Jöns Jakob Berzelius and Magnus Martin af Pontin, who had also been trying to isolate calcium. Davy eventually succeeded by electrolyzing calcium oxide together with mercury oxide. After the oxygen was removed, he boiled off the mercury, leaving pure calcium behind.

The metal is ductile and has a silvery color. Chemically, it is one of the alkaline earth elements; it readily forms a white coating of nitride in air, reacts with water to produce calcium hydroxide and hydrogen gas, and burns with a yellow-red flame.

The primary use of calcium is in the form of lime, as a building material. Similarly, gypsum or calcium sulfate, the fine white powder found in abundance at White Sands National Park in New Mexico, is used in plaster of Paris, which is used to make casts to set broken bones.

Various calcium compounds are also used in food supplements and pharmaceuticals. Calcium compounds are a key ingredient in toothpaste and in antacids.

Isolated calcium metal is valuable as a deoxidizer (or desulfurizer or decarburizer, for sulfur and carbon) in the production of other metals, such as chromium, thorium, uranium, and zirconium. It is also used in steelmaking. It forms useful alloys with aluminum, beryllium, copper, lead, and magnesium. The alloy with lead is used in car batteries.

Calcium forms a lot of important compounds, like calcium oxide, carbonate, carbide, chloride, cyanamide, hypochlorite, nitrate, and sulfide.

Calcium phosphate is the primary component of bones. There is about one kilogram of calcium in a typical human being, and 99 percent of that is found in our bones.

By mass, calcium is the fifth most abundant element in the earth's crust, after oxygen, sodium, aluminum, and iron. It is an essential constituent of bones, teeth, and shells. Never found in nature uncombined, calcium occurs abundantly as limestone (calcium carbonate), gypsum (calcium sulfate), and fluorite (calcium fluoride). Indeed, limestone is largely made from old corals, shell fragments, and fossilized debris.

In the United States and Canada, calcium is typically obtained by heating lime from limestone with aluminum to remove the oxygen. Russia and China typically use electrolysis of calcium chloride to remove the chlorine.