Silicon dioxide, commonly known as silica, is an oxide of silicon with the chemical formula SiO2. It is a prevalent compound found abundantly in nature, particularly in the form of quartz, making it a major constituent of sand in various regions worldwide. Silica exists in multiple minerals and synthetic products, appearing colorless or white in its pure form, although impurities can impart coloration. This compound plays a fundamental role in the composition of glass and exhibits a unique structure characterized by tetrahedral coordination of silicon atoms with surrounding oxygen atoms.
Structure and Properties
In most silicon dioxide structures, each silicon atom forms covalent bonds with four oxygen atoms, creating a three-dimensional network solid. This structural arrangement contrasts starkly with carbon dioxide, which is a linear molecule. Silicon dioxide can be categorized into crystalline and non-crystalline forms based on its crystal structure. The thermally grown silicon dioxide on silicon is typically amorphous, lacking a defined crystalline structure.
Applications and Safety
Silicon dioxide finds extensive use in various industries, including glass manufacturing and cement production. In the food industry, it serves as an anticaking agent to prevent clumping of powdered ingredients. While silicon dioxide is generally considered safe as a food additive when consumed in normal doses, inhaling fine particles of silica dust can pose health risks. Prolonged exposure to silica dust may lead to respiratory issues such as silicosis, lung cancer, and chronic obstructive pulmonary disease (COPD).
Natural Occurrence and Health Implications
Silicon dioxide is naturally present in numerous plants consumed by humans, such as dark leafy greens, grains, vegetables, and alfalfa. Despite concerns about its presence in food products, studies indicate that silicon dioxide poses minimal risk when ingested within regulatory limits. However, long-term inhalation of silica dust can have severe consequences on respiratory health and may increase the risk of certain diseases like tuberculosis.
In conclusion, silicon dioxide stands as a ubiquitous compound with diverse applications across industries and natural occurrences in various biological systems. While its safety as a food additive is generally accepted within specified limits, precautions must be taken to avoid prolonged exposure to silica dust to mitigate potential health hazards associated with inhalation.
[1][2][4]
Citations:
[1] https://en.wikipedia.org/wiki/Silicon_dioxide
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula SiO2, commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is abundant as it comprises several minerals and synthetic products. All forms are white or colorless, although impure samples can be colored.
 A sample of silicon dioxide | |
| Names | |
|---|---|
| IUPAC name Silicon dioxide | |
Other names
| |
| Identifiers | |
| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.028.678 |
| EC Number |
|
| E number | E551 (acidity regulators, ...) |
| 200274 | |
| KEGG | |
| MeSH | Silicon+dioxide |
PubChem CID | |
| RTECS number |
|
| UNII | |
CompTox Dashboard (EPA) | |
| |
| Properties | |
| SiO2 | |
| Molar mass | 60.08 g/mol |
| Appearance | Transparent or white |
| 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 (fire diamond) | |
| NIOSH (US health exposure limits): | |
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⦵298) | 42 J·mol−1·K−1 |
Std enthalpy of formation (ΔfH⦵298) | −911 kJ·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
Silicon dioxide is a common fundamental constituent of glass.
English
Noun
silicon dioxide (uncountable)
- (chemistry) A hard glassy mineral, SiO₂, occurring as quartz, sand, opal etc.