Uses of Calcium

The first known uses of calcium were by the Romans in the first century to make calcium oxide. Other written documentation around 975 C.E. suggests that plaster of Paris and Calcium Sulfate were medically useful. Calcium is available in a wide variety of forms, from limestone and chalk (calcium carbonate) to marble (calcite) and pearls. It also has many mineral forms (see link provided in Outside Links section). Calcium carbonate, in moderate amounts, can also be used as an antacid or a calcium supplement. Calcium nitrate is also a common fertilizer. Pure CaCO₃ can be extracted from limestone in a series of three reactions:

• Calcination:  
  CaCO₃→CaO+CO₂

• Slaking:  
  CaO+H₂O→Ca(OH)₂
• Carbonation: 
  Ca(OH)₂+CO₂→CaCO₃+H₂O

Fig. 2: A Blue Starfish resting on hard Acropora coral.