|
|
 |
| Physical Properties |
|
For all anhydrous calcium carbonates:
|
|
CaCO3 |
100,0
|
|
| Rel. molar mass |
Calcium
Carbon
Oxygen
|
40,0
12,0
48,0
|
percentage by weight
|
Crystallographic shapes of calcium carbonate:
SOLVAY Precipitated Calcium Carbonate is a synthetic calcium carbonate consisting of trigonal calcite crystals with cube-shaped particles or ortho-rhombic aragonite crystals with a needle-like structure. The calcite can also be precipitated in a trigonal scalenohedral particle form. The various SOCAL® crystal shapes are reproduced below.
|
Calcite
Trigonal-rhombohedral
|
Calcite
Trigonal-scalenohedral
|
Aragonite
Ortho-rhombic
|
|
|
|
|
Compared with dry or wet milled natural calcites or chalks, PCC can be distinguished through its finer and more uniform particle sizes, closer particle size distribution and a higher degree of chemical purity.
Characteristics of Calcite and Aragonite:
| Type |
CALCITE
|
ARAGONITE
|
| crystal system |
rhombohedral
|
orthorhombic
|
|
density
|
2.71
|
2.94
|
|
hardness acc. to MOHS
|
3 |
3.5
|
|
biaxial indicatrix
|
negative uniaxial
|
negative biaxial (2V=18°)
|
|
refractive index
|
ω = 1.486
ε = 1.658
|
α = 1.530
β = 1.680
γ = 1.685
|
|
birefringence
|
0.172
|
0.155
|
|
Infra-Red
absorption bands
(cm-1)
|
714
876
|
698
714
857
|
|
|
|
|
