Tin(IV) oxide, also known as stannic oxide, is the inorganic compound with the formula SnO2. The mineral form of SnO2 is called cassiterite, and this is the main ore of tin.[5] With many other names, this oxide of tin is an important material in tin chemistry. It is a colourless, diamagnetic, amphoteric solid.
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| Names | |
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| IUPAC name
Tin (IV) Oxide | |
Other names
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| Identifiers | |
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3D model (JSmol) |
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| ChemSpider | |
| ECHA InfoCard | 100.038.311 |
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PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties[1] | |
| SnO2 | |
| Molar mass | 150.708 g·mol−1 |
| Appearance | Gray tetragonal crystals |
| Density | 6.85 g/cm3 |
| Melting point | 1,630 °C (2,970 °F; 1,900 K) |
| Insoluble | |
| Solubility | Soluble in hot concentrated alkalis. |
| −41×10−6 cm3/mol | |
Refractive index (nD) |
2.006[2] |
| Structure[3] | |
| Rutile tetragonal, tP6 | |
| P42/mnm, No. 136 | |
| 4/m 2/m 2/m | |
a = 4.737 Å, c = 3.185 Å α = 90°, β = 90°, γ = 90° | |
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| Thermochemistry[1] | |
Heat capacity (C) |
52.6 J⋅mol−1·K-1 |
Std molar entropy (S⦵298) |
49.0 J⋅mol−1·K-1 |
Std enthalpy of formation (ΔfH⦵298) |
−577.6 kJ⋅mol−1 |
Gibbs free energy (ΔfG⦵) |
−515.8 kJ⋅mol−1 |
Enthalpy of fusion (ΔfH⦵fus) |
23.4 kJ⋅mol−1 |
| Hazards | |
| GHS labelling:[4] | |
| None | |
| None | |
| None | |
| NFPA 704 (fire diamond) | |
Threshold limit value (TLV) |
2 mg/m3[4] (TWA) |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) |
>20 g/kg (rat, oral)[4] |
LC50 (median concentration) |
2.04 mg/L (rat, inhaled, 4h)[4] |
| NIOSH (US health exposure limits):[4] | |
PEL (Permissible) |
2 mg/m3 (TWA) |
REL (Recommended) |
2 mg/m3 (TWA) |
IDLH (Immediate danger) |
100 mg/m3 |
| Related compounds | |
| Tin(II) oxide | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Structure
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Tin(IV) oxide crystallises with the rutile structure. As such the tin atoms are six coordinate and the oxygen atoms three coordinate.[5] SnO2 is usually regarded as an oxygen-deficient n-type semiconductor.[6]
Hydrous forms of SnO2 have been described as stannic acid. Such materials appear to be hydrated particles of SnO2 where the composition reflects the particle size.[7]
Preparation
editTin(IV) oxide occurs naturally. Synthetic tin(IV) oxide is produced by burning tin metal in air.[7] Annual production is in the range of 10 thousand metric tons (11 thousand short tons).[7] SnO2 is reduced industrially to the metal with carbon in a reverberatory furnace at 1,200–1,300 °C (2,190–2,370 °F).[8]
Reactions
editThe reaction from tin(IV) oxide with hot carbon monoxide is practiced on a large scale as this carbothermal reduction is used to obtain tin metal from its ores:
- SnO2 + 2 CO → Sn + 2 CO2
Some other reactions relevant to purifying tin from its ores are:[9]
- SnO2 + MgCl2 + CO → SnCl2 + MgO + CO2
- 4 SnO2 + 6 FeCl2 → 2 SnCl2 + 2 SnCl4 + 2 Fe3O4
SnO2 converts to the monoxide at 1,500 °C (2,730 °F):[9]
- 2 SnO2 → 2 SnO + O2
SnO2 is insoluble in water. It dissolves in sulfuric acid and in molten sodium hydroxide. It is not amphoteric. Like rutile, it is not attacked by solutions of acid or base.
Dissolution of SnO2 in sulfuric acid gives the sulfate:[7]
- SnO2 + 2 H2SO4 → Sn(SO4)2 + 2 H2O
The latter compound can add additional hydrogen sulfate ligands to give hexahydrogensulfatostannic acid.[10]
SnO2 dissolves in molten alkali to give "stannates," with the nominal formula Sodium stannate (Na2SnO3).[7] Dissolving the solidified SnO2/NaOH melt in water gives Na2[Sn(OH)6], "preparing salt," which is used in the dye industry.[7]
Uses
editIn conjunction with vanadium oxide, it is used as a catalyst for the oxidation of aromatic compounds in the synthesis of carboxylic acids and acid anhydrides.[5]
Ceramic glazes
editSnO2 is used as pigment in the manufacture of glasses, enamels and ceramic glazes. Thousands of tons of SnO2 are produced annually for this application. Pure SnO2 gives a milky white colour; other colours are achieved when mixed with other metallic oxides e.g. vanadium(V) oxide (V2O5) yellow; Chromium(III) oxide (Cr2O3) pink; and antimony pentoxide (Sb2O5) grey blue.[7][11] This use probably led to the discovery of the pigment lead-tin-yellow, which was produced using tin(IV) oxide as a compound.[12] The use of tin(IV) oxide has been particularly common in glazes for earthenware, sanitaryware and wall tiles; see the articles tin-glazing and Tin-glazed pottery. Tin oxide remains in suspension in vitreous matrix of the fired glazes, and, with its high refractive index being sufficiently different from the matrix, light is scattered, and hence increases the opacity of the glaze. The degree of dissolution increases with the firing temperature, and hence the extent of opacity diminishes.[13] Although dependent on the other constituents the solubility of tin oxide in glaze melts is generally low. Its solubility is increased by Na2O, K2O and B2O3, and reduced by CaO, BaO, ZnO, Al2O3, and to a limited extent PbO.[14]
Glass coatings
editSnO2 coatings are valued as transparent conducting oxides (TCOs). Like other TCOs, SnO2 has significant electrical conductivity but is transparent, an unusual combination of properties. Windows coated with SnO2 also reflect infrared radiation, which is relevant to temperature control for smart windows.[15] Coatings can be applied using chemical vapor deposition, vapour deposition techniques that employ tin(IV) chloride (SnCl4) or organotin trihalides e.g. butyltin trichloride as the volatile agent.[5][16][better source needed] This technique is used to coat glass bottles with a thin (<0.1 μm) layer of SnO2, which helps to adhere a subsequent, protective polymer coating such as polyethylene to the glass.[5]
Thicker layers doped with Sb or F ions are electrically conducting and used in electroluminescent devices and photovoltaics.[5]
Gas sensing
editSnO2 has been evaluated as sensors of combustible gases including carbon monoxide detectors. In these the sensor area is heated to a constant temperature (few hundred °C) and in the presence of a combustible gas the electrical resistivity drops.[17]
Historical uses
editThis oxide of tin has been utilized as a mordant in the dyeing process since ancient Egypt.[18] A German by the name of Kuster first introduced its use to London in 1533 and by means of it alone, the color scarlet was produced there.[19]
Tin(IV) oxide for this use is sometimes called as "putty powder" or "jeweler's putty".[20]
Polishing
editTin(IV) oxide can be used as a polishing powder, sometimes in mixtures also with lead oxide, for polishing glass, jewelry, marble and silver.[7]
References
edit- 1 2 Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). Boca Raton, Florida: CRC Press. pp. 4–91, 4–131, 5–39, 6–162. ISBN 9781498754293.
- ↑ Pradyot, Patnaik (2003). Handbook of Inorganic Chemicals. The McGraw-Hill Companies, Inc. p. 940. ISBN 0-07-049439-8.
- ↑ Baur, W.H. (1956). "Über die Verfeinerung der Kristallstrukturbestimmung einiger Vertreter des Rutiltyps: TiO2, SnO2, GeO2 und MgF2". Acta Crystallographica. 9 (6): 515–520. Bibcode:1956AcCry...9..515B. doi:10.1107/S0365110X56001388.
- 1 2 3 4 5 6 "SDS - Tin(IV) oxide". www.fishersci.com. Revision 6. ThermoFisher Scientific. December 21, 2025 [22 September 2009]. Retrieved July 9, 2026.
- 1 2 3 4 5 6 Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 447–48. ISBN 978-0-08-022057-4.
- ↑ Smart, Lesley; Moore, Elaine (2005). Solid state chemistry: an introduction (3rd ed.). Boca Raton: CRC Press. ISBN 0-7487-7516-1.[page needed]
- 1 2 3 4 5 6 7 8 Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, ISBN 0-12-352651-5
- ↑ Wardell, J.L. (1994). "Tin: Inorganic Chemistry". In Bruce King, R. (ed.). Encyclopedia of Inorganic Chemistry. Chichester ; New York: John Wiley & Son. ISBN 0-471-93620-0.[page needed]
- 1 2 Graf, Günter G. (2000). "Tin, Tin Alloys, and Tin Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a27_049. ISBN 978-3-527-30673-2.
- ↑ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. p. 844. ISBN 978-0-08-022057-4.
- ↑ Searle, A.B. (1935). The Glazer's Book - The Practical Application Of Recipes And Processes To Glazes For Bricks And Tiles (2nd ed.). London: The Technical Press Ltd.[page needed]
- ↑ Kühn, Hermann (1967). "Blei-Zinn-Gelb und seine Verwendung in der Malerei" [Lead-tin Yellow and its use in Painting]. Farbe und Lack [Paint and Varnish] (in German). 73: 938–949.
- ↑ Bourry, E. (1926). A Treatise On Ceramic Industries (4th ed.). London: Scott, Greenwood & Son.[page needed]
- ↑ Parmelee, C.W; Harman, C.G. (1973). Ceramic Glazes (3rd ed.). Boston, MA: Cahners Books.[page needed]
- ↑ Batzill, Matthias; Diebold, Ulrike (2005). "The surface and materials science of tin oxide". Progress in Surface Science. 79 (2–4): 47–154. Bibcode:2005PrSS...79...47B. doi:10.1016/j.progsurf.2005.09.002.
- ↑ US 4130673, Larkin, William A., "Process of applying tin oxide on glass using butyltin trichloride", published December 19, 1978, assigned to M & T Chemicals Inc.
- ↑ Watson, Joseph (2006). "The Stannic Oxide Semiconductor Gas Sensor". In Dorf, R.C. (ed.). The Electrical Engineering Handbook. Sensors, Nanoscience, Biomedical engineering, and Instruments (3rd ed.). Boca Raton: CRC/Taylor & Francis. ISBN 0-8493-7346-8.
- ↑ Thorpe, Sir Thomas Edward (1909). History of Chemistry. Vol. 1. pp. 11–12.
- ↑ Mortimer, Thomas (1810). "Dying or Dyeing". A General Dictionary of Commerce, Trade, and Manufactures. p. 139.
- ↑ Sherwood, F.; Taylor, Heineman (1942). Inorganic & Theoretical chemistry (6th ed.).[page needed]