Germanium dioxide

Germanium dioxide

tetragonal rutile form
Names
IUPAC name Germanium dioxide
Other names Germanium(IV) oxide Germania ACC10380 G-15 Germanium oxide Germanic oxide
Identifiers
CAS Number	1310-53-8 Y
3D model (Jmol)	Interactive image
ChemSpider	14112 Y
ECHA InfoCard	100.013.801
PubChem	14796
RTECS number	LY5240000
UNII	5O6CM4W76A Y
InChI InChI=1S/GeO2/c2-1-3 Y Key: YBMRDBCBODYGJE-UHFFFAOYSA-N Y InChI=1/GeO2/c2-1-3 Key: YBMRDBCBODYGJE-UHFFFAOYAG
SMILES O=[Ge]=O
Properties
Chemical formula	GeO2
Molar mass	104.6388 g/mol
Appearance	white powder or colourless crystals
Density	4.228 g/cm3
Melting point	1,115 °C (2,039 °F; 1,388 K)
Solubility in water	4.47 g/L (25 °C) 10.7 g/L (100 °C)
Solubility	soluble in HF, insoluble in other acid and alkali
Magnetic susceptibility (χ)	−34.3·10−6 cm3/mol
Refractive index (nD)	1.650
Structure
Crystal structure	hexagonal
Hazards
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (median dose)	3700 mg/kg (rat, oral)
Related compounds
Other anions	Germanium disulfide Germanium diselenide
Other cations	Carbon dioxide Silicon dioxide Tin dioxide Lead dioxide
Related compounds	Germanium monoxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Germanium dioxide, also called germanium oxide and germania, is an inorganic compound with the chemical formula GeO₂. It is the main commercial source of germanium. It also forms as a passivation layer on pure germanium in contact with atmospheric oxygen.

The two predominant polymorphs of GeO₂ are hexagonal and tetragonal. Hexagonal GeO₂ has the same structure as β-quartz, with germanium having coordination number 4. Tetragonal GeO₂ (the mineral argutite) has the rutile-like structure seen in stishovite. In this motif, germanium has the coordination number 6. An amorphous (glassy) form of GeO₂ is similar to fused silica.

Germanium dioxide can be prepared in both crystalline and amorphous forms. At ambient pressure the amorphous structure is formed by a network of GeO₄ tetrahedra. At elevated pressure up to approximately 9 GPa the germanium average coordination number steadily increases from 4 to around 5 with a corresponding increase in the Ge-O bond distance. At higher pressures, up to approximately 15 GPa, the germanium coordination number increases to 6 and the dense network structure is composed of GeO₆ octahedra. When the pressure is subsequently reduced, the structure reverts to the tetrahedral form. At high pressure, the rutile form converts to an orthorhombic CaCl₂ form.

Heating germanium dioxide with powdered germanium at 1000 °C forms germanium monoxide (GeO).

The hexagonal (d = 4.29 g/cm3) form of germanium dioxide is more soluble than the rutile (d = 6.27 g/cm3) form and dissolves to form germanic acid, H₄GeO₄ or Ge(OH)₄. GeO₂ is only slightly soluble in acid but dissolves more readily in alkali to give germanates.