Silicon dioxide

Silicon dioxide
	; A sample of silicon dioxide
Names
	IUPAC name Silicon dioxide
	Other names Quartz; Silica; Silicic oxide; Silicon(IV) oxide; Crystalline silica; Pure Silica; Silicea; Silica sand;
Identifiers
CAS Number	7631-86-9 ;
ChEBI	CHEBI:30563 ;
ChemSpider	22683 ;
ECHA InfoCard	100.028.678
EC Number	231-545-4;
E number	E551 (acidity regulators, ...)
Gmelin Reference	200274
KEGG	C16459 ;
MeSH	Silicon+dioxide
PubChem CID	24261;
RTECS number	VV7565000;
UNII	ETJ7Z6XBU4 ;
CompTox Dashboard (EPA)	DTXSID1029677 ;
	InChI InChI=1S/O2Si/c1-3-2 Key: VYPSYNLAJGMNEJ-UHFFFAOYSA-N ;
Properties
Chemical formula	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)
Magnetic susceptibility (χ)	−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)	0 0 0
	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; Germanium dioxide; Tin dioxide; Lead dioxide
Related compounds	Silicon monoxide; Silicon sulfide
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). verify (what is ?) Infobox references

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.

Silicon dioxide is a common fundamental constituent of glass.

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