The Online Encyclopedia and Dictionary






Silicon dioxide

Name Silicon dioxide
Chemical formula SiO2
Appearance Transparent solid
Formula weight 60.1 amu
Melting point 1986 K (1713 °C)
Boiling point 2503 K (2230 °C)
Density 2.6 ×103 kg/m3
Crystal structure Quartz, cristobalite or tridymite
Solubility 0.012 g in 100g water
ΔfH0gas -305.43 kJ/mol
ΔfH0liquid -899.86 kJ/mol
ΔfH0solid -910.86 kJ/mol
S0gas, 1 bar 228.98 J/mol·K
S0liquid, 1 bar  ? J/mol·K
S0solid 41.46 J/mol·K
Ingestion Low hazard.
Inhalation Irritation, long term exposure of the crystalline form causes silicosis.
Skin May cause irritation.
Eyes May cause irritation.
More info Hazardous Chemical Database
SI units were used where possible. Unless otherwise stated, standard conditions were used.

Disclaimer and references

The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2.

It is found in nature in several forms, including quartz and opal. In fact, silica has 17 crystalline forms. Also, many forms of life include silica structures, including microorganisms such as diatoms, plants such as horsetail, and animals such as hexactinellid sponges.

It is manufactured in several forms including glass (in colorless high purity form called fused silica), synthetic amorphous silica and silica gel (used e.g. as desiccants in brand new clothes and leather goods). Silica is a major ingredient of Portland cement. The ceramic re-entry heat protection tiles mounted on the bottom side of the Space Shuttles are made mostly of silica, as are the firebricks used in steel processing.

Inhaling crystalline silica dust can lead to silicosis.

Further reading

Last updated: 08-20-2005 02:49:49
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