Tin (IV) oxide

Crystal structure
__ Sn 4+      __ O 2−
General
Surname	Tin (IV) oxide
other names	Tin ash Pewter flowers Tin dioxide Stannic anhydride Tin white TIN OXIDE ( INCI )
Ratio formula	SnO 2
Brief description	amorphous, white powder or hexagonal, tetragonal or rhombic crystals
External identifiers / databases
CAS number 18282-10-5 EC number 242-159-0 ECHA InfoCard 100.038.311 PubChem 29011 Wikidata Q129163
properties
Molar mass	150.71 g · mol -1
Physical state	firmly
density	6.95 g cm −3 (20 ° C)
Melting point	1630 ° C
solubility	almost insoluble in water soluble in concentrated hydrochloric acid and nitric acid
Refractive index	1.9968 (20 ° C)
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
Toxicological data	> 20000 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Tin (IV) oxide , also known as tin dioxide , is the main component of the mineral cassiterite (tin stone) and the main source of pure tin .

Extraction and presentation

Tin (IV) oxide can be obtained by burning tin in air , by reacting tin (IV) chloride and water (both as steam) at high temperatures, and by reacting tin with sulfuric acid and then with hydroxides .

Chemical properties

The water-insoluble, amphoteric tin dioxide dissolves in strong acids such as hydrochloric acid or hydriodic acid with the formation of the corresponding hexahalogen stannates:

${\displaystyle \mathrm {SnO_{2}\ +\ 6\ HI\ \longrightarrow \ \ H_{2}[SnI_{6}]\ +\ 2\ H_{2}O} }$

The salts of the partly free non-existent tin acids H ₂ [Sn (OH) ₆ ] and H ₂ SnO ₃ ( metatin (IV) acid ) are formed with strong alkalis . The corresponding alkali salts such as Na ₂ SnO ₃ or Na ₂ [Sn (OH) ₆ ] are stable and are used in the dyeing industry , such as the sodium stannate Na ₂ [Sn (OH) ₆ ].

use

Tin (IV) oxide is used as a semiconductor ingredient, such as together with antimony oxide (III) as ATO , Antimony-Tin-Oxide and as FTO ( Fluorine doped Tin Oxide ), for the photovoltaic in Grätzel cell used. Tin dioxide is also used in optical fibers or LC displays - here it serves as a transparent, electrically conductive layer - and in gas sensors , where it reacts with a change in resistance to all oxidizable gases or vapors.

It is also used as a polishing powder for steel , glass and natural stone , as a white, transparent opacifier in the production of ceramic glazes , milk glass and enamel , for sealing cracks in glass and as a catalyst in chemical processes. Tin (IV) oxide used to be used as a glaze in the manufacture of faience . It is also used as an electrode material when melting inorganic glasses. It is mainly used as a replacement for molybdenum electrodes when melting lead glasses .

In electromechanical switchgear such as B. Protect , the contact material often consists of silver with 2–14% by weight SnO ₂ . Since many manufacturers have avoided cadmium in particular , the previously used cadmium oxide has been replaced by tin oxide.

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  Powdered tin dioxide

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  Cassiterite

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  Faience bowl with tin dioxide glaze (1629)

Individual evidence

1. ↑ Entry on TIN OXIDE in the CosIng database of the EU Commission, accessed on February 17, 2020.
2. ↑ ^{a b c} Entry on tin oxides. In: Römpp Online . Georg Thieme Verlag, accessed on December 22, 2014.
3. ↑ ^{a b c d} Entry on tin dioxide in the GESTIS substance database of the IFA , accessed on December 19, 2019(JavaScript required) .
4. ↑ Data sheet Tin (IV) oxide, Puratronic®, 99.996% (metals basis) from AlfaAesar, accessed on February 1, 2017 ( PDF )(JavaScript required) .
5. ^ Donaldson & Grimes: Chemistry of tin ed. PG Harrison Blackie (1989).
6. ↑ Earle R. Caley: The Action Of Hydriodic Acid On Stannic Oxide . In: J. Am. Chem. Soc. , 1932, 54, 8, pp. 3240-3243, doi : 10.1021 / ja01347a028 .

Web links

• optical properties (PDF; 400 kB)