Silica
 |
|
| Names | |
|---|---|
|
IUPAC name
Silicon dioxide
|
|
| Other names
Quartz
Silica |
|
| Identifiers | |
7631-86-9 
|
|
| ChEBI |
CHEBI:30563
|
| ChemSpider |
22683
|
| ECHA InfoCard | 100.028.678 |
| EC Number | 231-545-4 |
| E number | E551 (acidity regulators, ...) |
| 200274 | |
| KEGG |
C16459 
|
| MeSH | Silicon+dioxide |
| PubChem | 24261 |
| RTECS number | VV7565000 |
| UNII |
ETJ7Z6XBU4
|
|
|
| Properties | |
| SiO2 | |
| Molar mass | 60.08 g/mol |
| Appearance | Transparent solid (Amorphous) White/Whitish Yellow (Powder/Sand) |
| Density | 2.648 (α-quartz), 2.196 (amorphous) g·cm−3 |
| Melting point | 1,713 °C (3,115 °F; 1,986 K) (amorphous) to |
| Boiling point | 2,950 °C (5,340 °F; 3,220 K) |
| −29.6·10−6 cm3/mol | |
| Thermal conductivity | 12 (|| c-axis), 6.8 (⊥ c-axis), 1.4 (am.) W/(m⋅K) |
|
Refractive index (nD)
|
1.544 (o), 1.553 (e) |
| Hazards | |
| NFPA 704 | |
| US health exposure limits (NIOSH): | |
|
PEL (Permissible)
|
TWA 20 mppcf (80 mg/m3/%SiO2) (amorphous) |
|
REL (Recommended)
|
TWA 6 mg/m3 (amorphous) Ca TWA 0.05 mg/m3 |
|
IDLH (Immediate danger)
|
3000 mg/m3 (amorphous) Ca [25 mg/m3 (cristobalite, tridymite); 50 mg/m3 (quartz)] |
| Related compounds | |
|
Related diones
|
Carbon dioxide |
|
Related compounds
|
Silicon monoxide |
| Thermochemistry | |
|
Std molar
entropy (S |
42 J·mol−1·K−1 |
|
Std enthalpy of
formation (ΔfH |
−911 kJ·mol−1 |
|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|
|
 (what is ?) |
|
| Infobox references | |
Silica
Silicic oxide
Silicon(IV) oxide
Germanium dioxide
Tin dioxide
Lead dioxide
Silicon dioxide, also known as silica (from the Latin silex), is a chemical compound that is an oxide of silicon with the chemical formula SiO2. It has been known since ancient times. Silica is most commonly found in nature as quartz, as well as in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing both as several minerals and being produced synthetically. Notable examples include fused quartz, crystal, fumed silica, silica gel, and aerogels. Applications range from structural materials to microelectronics to components used in the food industry.
Silicon dioxide is mostly obtained by mining and purification of quartz. Quartz comprises more than 10% by mass of the earth's crust. This product is suitable for many purposes while for others chemical processing is required to make a purer or otherwise more suitable (e.g. more reactive or fine-grained) product.
Pyrogenic silica (sometimes called fumed silica or silica fume) is a very fine particulate or colloidal form of silicon dioxide. It is prepared by burning SiCl4 in an oxygen rich hydrocarbon flame to produce a "smoke" of SiO2.
This product is obtained as byproduct from hot processes like ferro-silicon production. It is less pure than fumed silica and should not be confused with that product. The production process, particle characteristics and fields of application of fumed silica are all different from those of silica fume.
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Wikipedia