Chemistry Forum

Calcium carbonate or CaCO₃ is one of chemical compound found in the rocks as a mineral calcite and aragonite mostly particularly as a limestone, chalk or a marble. Although the fact that they are available in various forms they are chemically similar but differ physically. They differ in terms of whiteness, thickness, purity and homogeneity.

Similar to limestone, calcium carbonate is a biogenic rock, and is more compressed than chalk. Calcium-carbonate is a bristly-crystalline, metamorphic rock alike marble that is formed when chalk or limestone is re-crystallized. Huge sediments of marble are obtained in North America and in Europe for example in Carrara, Italy, where the pure white "statuario marble" is found. Calcium carbonate crystals are also described as calcite.

How calcium carbonate is prepared?

The massive amount of bulk calcium carbonate used in industry is obtained by excavating or mining. Calcium carbonate can be produced from pure quarried source which is used for food and pharmaceutical industry.

However, calcium carbonate is made from oxides of calcium. Calcium oxide is dissolved in water to form calcium hydroxide. To precipitate the desired solution carbon dioxide is passed through calcium hydroxide which is signified as precipitated calcium carbonate (PPC).

CaO + H₂O -> Ca (OH) 2

Calcium oxide + Water → Calcium hydroxide

Ca (OH) 2 + CO₂ → CaCO₃ + H₂O

Calcium hydroxide + Carbon dioxide → Calcium carbonate

Occurrence in the earth

Geological sources

Pure forms of calcium carbonate are calcite, aragonite and vaterite. Significant source of calcium carbonate include limestone, chalk and marble.

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Already posted 9 days before.

ChenBeier wrote: ↑Mon Oct 16, 2017 3:53 am Already and posted 9 years before.

Fascinating info on alumina. I wasn't aware that Hall-Heroult Process uses over 90 percent of it.