Silicon dioxide : Silica

**Properties**
General
Name	Silicon dioxide
Chemical formula	Si O₂
Appearance	Transparent solid
Physical
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
Thermochemistry
Δ_fH⁰_gas	-305.43 kJ/mol
Δ_fH⁰_liquid	-899.86 kJ/mol
Δ_fH⁰_solid	-910.86 kJ/mol
S⁰_{gas, 1 bar}	228.98 J/mol·K
S⁰_{liquid, 1 bar}	? J/mol·K
S⁰_solid	41.46 J/mol·K
Safety
Ingestion	Low hazard.
Inhalation	Irritation, long term exposure causes silicosis[?].
Skin	May cause irritation.
Eyes	May cause irritation.
More info	Hazardous Chemical Database (http://ull.chemistry.uakron.edu/erd/chemicals/10/9916.html)
SI units were used where possible. Unless otherwise stated, standard conditions were used. Disclaimer and references

Silicon dioxide, also known as silica is the naturally occurring oxide of silicon, chemical formula SiO₂.

It is found in nature in several forms, including sand and quartz and is also a major constituent of many minerals, including flint.

It is also manufactured in several forms including glass and silica gel. It is a major ingredient of Portland cement.

Inhaling silica dust can lead to silicosis[?].