Amorphous silica
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| Names | |
|---|---|
|
IUPAC name
Silicon dioxide
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|
| Other names
Quartz
Silica |
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| Identifiers | |
| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.028.678 |
| EC Number | 231-545-4 |
| E number | E551 (acidity regulators, ...) |
| 200274 | |
| KEGG | |
| MeSH | Silicon+dioxide |
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PubChem CID
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| RTECS number | VV7565000 |
| UNII | |
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| 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)
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TWA 20 mppcf (80 mg/m3/%SiO2) (amorphous) |
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REL (Recommended)
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TWA 6 mg/m3 (amorphous) Ca TWA 0.05 mg/m3 |
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IDLH (Immediate danger)
|
3000 mg/m3 (amorphous) Ca [25 mg/m3 (cristobalite, tridymite); 50 mg/m3 (quartz)] |
| Related compounds | |
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Related diones
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Carbon dioxide |
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Related compounds
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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).
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|
 (what is   ?) |
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| 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 an oxide of silicon with the chemical formula SiO2, most commonly found in nature as quartz and 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 as a compound of several minerals and as synthetic product. Notable examples include fused quartz, fumed silica, silica gel, and aerogels. It is used in structural materials, microelectronics as component in the food and pharmaceutical industry.
Inhaling finely divided crystalline silica is toxic and can lead to silicosis, bronchitis, lung cancer and systemic autoimmune diseases, such as lupus and rheumatoid arthritis.
In the majority of silicates, the Si atom shows tetrahedral coordination, with four oxygen atoms surrounding a central Si atom. The most common example is seen in the quartzite polymorph.
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