Calcium carbonate

Calcium carbonate ;
Names:	calcium carbonate; Е170 food additive;
Formula:	CaCO3;
Molar mass:	100.086 g/mol;
Density:	2.74 g/cm3 (calcite); 1.77 g/cm3 (aragonite);
Crystal system:	rhombohedral (calcite); a=6.36 Å, b=6.36 Å, c=6.36 Åα=46.1°, β=46.1°, γ=46.1°; orthorhombic (aragonite); a=5.7394 Å, b=4.9616 Å, c=7.97 Åα=90°, β=90°, γ=90°; hexagonal (vaterite); a=4.9915 Å, b=4.9915 Å, c=17.088 Åα=90°, β=90°, γ=120°;
Shapes:	https://en.crystalls.info/w/uploads/media/3/36/Oblique_rhombic_prism.json Oblique rhombic prism https://en.crystalls.info/w/uploads/media/5/52/Needle.json Needle https://en.crystalls.info/w/uploads/media/f/fc/Spherolit.json Spherolit https://en.crystalls.info/w/uploads/media/2/28/Prolongated_tetragonal_pyramidal_prism.json Prolongated tetragonal pyramidal prism ;
Color:	white; colorless;
Melting point:	825 °C1,098.15 K <br />1,517 °F <br />1,976.67 °R <br />;
Decomposition point:	1000 °C1,273.15 K <br />1,832 °F <br />2,291.67 °R <br /> (calcite);
Refractive index:	1.59 (calcite); 1.51 (aragonite);
Optical properties:	birefringence;
Magnetic properties:	diamagnetic; χ=-3.82 · 10-5cm³/mol;
Hardness:	very fragile;
Toxicity:	non-toxic; LD50=6450mg/kg

Description

Inorganic compound, salt of alkaline earth metal calcium and inorganic carbonic acid. Doesn't form water hydrates.

Minerals

Occurs in nature as calcite, aragonite, vaterite, chalk, marble, travertine, ikaite, glendonite and pearl minerals.

Where to buy

Can be bought in hardware store (as "marble crumb", "marble flour"), office supply store (as "chalk" - mixed calcium carbonate and sulfate) and fertilizers store.

Precursors

Reaction between calcium chloride or nitrate and baking soda, sodium carbonate or potassium carbonate

Chemical equation:

Ca(NO₃)₂ + 2NaHCO₃ = CaCO₃↓ + 2NaNO₃ + H₂O + CO₂↑

Ca(NO₃)₂ + Na₂CO₃ = CaCO₃↓ + 2NaNO₃

Ca(NO₃)₂ + K₂CO₃ = CaCO₃↓ + 2KNO₃

CaCl₂ + 2NaHCO₃ = CaCO₃↓ + 2NaCl + H₂O + CO₂↑

CaCl₂ + Na₂CO₃ = CaCO₃↓ + 2NaCl

CaCl₂ + K₂CO₃ = CaCO₃↓ + 2KCl

For preparation of 100.00g of calcium carbonate а 235.94g of calcium nitrate

tetrahydratetetrahydrate
anhydrous

or 218.89g of calcium chloride

hexahydratehexahydrate
anhydrous

and 167.87g of soda or 105.90g of sodium carbonate or 138.09g of potassium carbonate is required.

Take two plastic or glass containers connected with a tube at center or bottom. Connection should be hermetic.

Place silicic acid gel in the tube.
Then add solution of calcium nitrate or chloride to the first container and soda, sodium or potassium carbonate to the another one. Pour solutions simultaneously otherwise gel will pour out from tube. Cover containers with a cap (you can leave them non-hermetic) and leave for long time at room temperature.
During long time reagents will slowly diffuse deeper into the thickness the gel, reacts with small parts if meeting. A slow crystal growing of the slight soluble reaction product will begin.

Notes

Grows with simultaneous synthesis. Evaporation or cooling method could not be used because of the extremely low solubility.

Storage conditions

Keep in its original form or under several layers of varnish at average humidity and room temperature. Do not keep crystals near heaters.

Solubility

TableGraph

Temperature	g/`100,00` g water
20°C293.15 K <br />68 °F <br />527.67 °R <br />	`0.001437`
25°C298.15 K <br />77 °F <br />536.67 °R <br />	`0.001522`

Insoluble in ethanol.

Gallery

Growth in the gelCalcium carbonate, Sergey Sachkov, VKontakteSergey SachkovVKontakte
Growth in the gelCalcium carbonate, Sergey Sachkov, VKontakteSergey SachkovVKontakte
Growth in the gelCalcium carbonate, Sergey Sachkov, VKontakteSergey SachkovVKontakte
Growth in the gelCalcium carbonate, Sergey Sachkov, VKontakteSergey SachkovVKontakte
Growth in the gelCalcium carbonate, Sergey Sachkov, VKontakteSergey SachkovVKontakte
Growth in the gelCalcium carbonate, Sergey Sachkov, VKontakteSergey SachkovVKontakte

Video

Sources

Carbonates
Salts	Calcium carbonate (CaCO₃) • Magnesium hydrocarbonate (Mg(HCO₃)₂) • Sodium carbonate (Na₂CO₃) • Sodium hydrocarbonate (NaHCO₃)
Complexes	Sodium dicarbonatocuprate(II) (Na₂[Cu(CO₃)₂])

Calcium compounds
Salts	Calcium acetate (Ca(CH₃COO)₂) • Calcium carbonate (CaCO₃) • Calcium formate (Ca(COOH)₂) • Calcium nitrate (Ca(NO₃)₂) • Calcium sulfate (CaSO₄) • Calcium tartrate (CaC₄H₄O₆) • Calcium trifluoroacetate (Ca(CF₃COO)₂) • Calcium chloride (CaCl₂)
Double salts	Copper-calcium acetate (CuCa(CH₃COO)₄) • Calcium-ammonium nitrate (5Ca(NO₃)₂ · NH₄NO₃)

Calcium carbonate
Names:	calcium carbonate Е170 food additive
Formula:	CaCO₃
Molar mass:	100.086 g/mol
Density:	2.74 g/cm³ (calcite) 1.77 g/cm³ (aragonite)
Crystal system:	rhombohedral (calcite) a=6.36 Å, b=6.36 Å, c=6.36 Åα=46.1°, β=46.1°, γ=46.1° orthorhombic (aragonite) a=5.7394 Å, b=4.9616 Å, c=7.97 Åα=90°, β=90°, γ=90° hexagonal (vaterite) a=4.9915 Å, b=4.9915 Å, c=17.088 Åα=90°, β=90°, γ=120°
Shapes:	Oblique rhombic prism Needle Spherolit Prolongated tetragonal pyramidal prism
Color:	white colorless
Melting point:	825 °C1,098.15 K <br />1,517 °F <br />1,976.67 °R <br />
Decomposition point:	1000 °C1,273.15 K <br />1,832 °F <br />2,291.67 °R <br /> (calcite)
Refractive index:	1.59 (calcite) 1.51 (aragonite)
Optical properties:	birefringence
Magnetic properties:	diamagnetic χ=-3.82 · 10^-5cm³/mol
Hardness:	very fragile
Toxicity:	non-toxic LD₅₀=6450mg/kg