Calcium carbonate

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  Calcium carbonate   
Names: calcium carbonate

Formula: CaCO3
SMILES: C(=O)([O-])[O-].[Ca+2]
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
6.3600 Å
0.6360 nm
, b=6.36 Å
6.3600 Å
0.6360 nm
, c=6.36 Å
6.3600 Å
0.6360 nm
α=46.1°
46°6′  
, β=46.1°
46°6′  
, γ=46.1°
46°6′  

orthorhombic (aragonite)
a=5.7394 Å
5.7394 Å
0.5739 nm
, b=4.9616 Å
4.9616 Å
0.4962 nm
, c=7.97 Å
7.9700 Å
0.7970 nm
α=90°
90°  
, β=90°
90°  
, γ=90°
90°  

hexagonal (vaterite)
a=4.9915 Å
4.9915 Å
0.4992 nm
, b=4.9915 Å
4.9915 Å
0.4992 nm
, c=17.088 Å
17.0880 Å
1.7088 nm
α=90°
90°  
, β=90°
90°  
, γ=120°
120°  

Shapes:
https://media.crystalls.info/w/uploads/media/Oblique_rhombic_prism.json
https://media.crystalls.info/w/uploads/media/Needle.json
https://media.crystalls.info/w/uploads/media/Spherolit.json
https://media.crystalls.info/w/uploads/media/Prolongated_tetragonal_pyramidal_prism.json

Color: white
colorless
Melting point: 825 °C
1,098.15 K
1,517 °F
1,976.67 °R

Decomposition point: 1000 °C
1,273.15 K
1,832 °F
2,291.67 °R
(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

In hardware store (as "marble crumb", "marble flour"), office supply store (as "chalk" - mixed calcium carbonate and sulfate), fertilizers store and grocery store (eggshell).

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 tetrahydrate or 218.89g of calcium chloride hexahydrate 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

Store in its original form or under several layers of varnish at average humidity and room temperature. Do not store in matchboxes or cotton wool and do not heat.

Solubility

Temperatureгр/100,00 гр water
20°C
293.15 K
68 °F
527.67 °R
0.001437
0.00144 g/100g
0.00144 %
25°C
298.15 K
77 °F
536.67 °R
0.001522
0.00152 g/100g
0.00152 %
Insoluble in ethanol.

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