Sir Humphry Davy discovered calcium in 1808 by isolating the impure metal through the electrolysis of a lime and mercuric oxide mixture. He accomplished this by studying the preparation of calcium amalgam through the electrolysis of lime in mercury.
The term calcium comes from the Latin word calx, which means lime. The Romans had prepared lime, limestone and other calcium compounds under the name calx. People used lime for hundreds of years to create plaster and mortar.
Antoine Lavoisier categorized lime as an “earth,” as it didn’t seem feasible to reduce the calcium compound further. However, he surmised that lime was likely an oxide of an unknown element. Sir Humphry Davy attempted to reduce damp lime using electrolysis in the same way that he reduced sodium and potassium, but his experiment did not go well. He tried again by using a mixture of lime and mercury oxide, and he was able to produce an amalgam of calcium and mercury. However, this wasn’t sufficient to verify the discovery of a new element. Jons Jacob Berzelius also performed a similar experiment and gained the same results. Davy then decided to add more lime to the mixture. He was able to produce more of the amalgam and distilled off the mercury, thus successfully obtaining calcium.