What Is Calcium and Why Do We Need It in Everyday Life?
Calcium is a silvery white metal. It has the chemical symbol Ca. It is one of the commonest metals in the Earth’s crust. It reacts easily with many other elements, and so is only found as a compound. Calcium carbonate occurs as chalk, limestone and marble.
Lime (calcium oxide, CaO) was the useful material obtained by heating limestone and used for centuries to make plaster and mortar. Antoine Lavoisier classified it as an ‘earth’ because it seemed impossible to reduce it further, but he suspected it was the oxide of an unknown element.
In 1808, Humphry Davy tried to reduce moist lime by electrolysis, just as he had done with sodium and potassium, but he was not successful. So he tried a mixture of lime and mercury oxide and while this produced an amalgam of calcium and mercury, it was not enough to confirm that he’d obtained a new element. (Jöns Jacob Berzelius had conducted a similar experiment and also obtained the amalgam.)
Davy tried using more lime in the mixture and produced more of the amalgam from which he distilled off the mercury leaving just calcium.
It is used in many products from toothpaste to concrete. Calcium phosphate is used in fertilizers. Calcium sulphate is found as gypsum and anhydrite. It is used in building materials, and blackboard chalk is made of calcium sulphate. Calcium compounds cause hardness of water.
Calcium is also a very important element in both plant and animal life. Calcium is essential to all living things, particularly for the healthy teeth and growth of bones. Much of the food we eat contains calcium. We need it to strengthen our bones and teeth.
Calcium phosphate is the main component of bone. Children and pregnant women are encouraged to eat foods rich in calcium, such as milk and dairy products, leafy green vegetables, fish and nuts and seeds. The average human contains about 1 kilogram of calcium.