Silver bromide

Crystal structure
__ Ag +      __ Br -
Crystal system	cubic
Space group	Fm 3 m (No. 225)
Coordination numbers	Ag [6], Br [6]
General
Surname	Silver bromide
Ratio formula	AgBr
Brief description	white to yellowish green solid
External identifiers / databases
CAS number 7785-23-1 EC number 232-076-8 ECHA InfoCard 100.029.160 PubChem 66199 ChemSpider 59584 Wikidata Q407515
properties
Molar mass	187.77 g mol −1
Physical state	firmly
density	6.47 g cm −3
Melting point	430 ° C
boiling point	1502 ° C
solubility	almost insoluble in water, 0.14 mg l −1 (25 ° C)
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 410 P: 273-391-501
Thermodynamic properties
ΔH f 0	−100.4 kJ / mol
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Silver bromide is a chemical compound of silver that is one of the bromides . It is a widely used chemical in photochemistry that breaks down when exposed to light.

Occurrence

Silver bromide occurs naturally in the form of the mineral bromogyrite .

Extraction and presentation

Silver bromide precipitates out as a yellowish-whitish precipitate when silver salt, usually silver nitrate, and a soluble bromine salt meet.

${\displaystyle \mathrm {AgNO_{3}+KBr\longrightarrow AgBr\downarrow +\ KNO_{3}} }$

The compound can also be obtained by reacting silver with bromine under excess pressure at 500 ° C.

properties

Silver bromide

Dry freshly extracted silver bromide looks yellowish. Its melt is orange-red. It is very difficult in water, difficult in concentrated ammonia solution and easily soluble in thiosulphate and cyanide solution. It quickly turns dark in the light as a result of silver deposition through photolytic decomposition . Silver bromide has a cubic crystal structure of the sodium chloride type.

use

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The salt is stored in small crystal fragments in a gelatin layer (or similar substances). When light falls on this, the silver bromide decomposes into its elementary components - silver and bromine ; the bromine evaporates. The exposed crystals stand out from the background because the finely divided silver appears black.

Individual evidence

1. ↑ Entry on silver bromide. In: Römpp Online . Georg Thieme Verlag, accessed on November 12, 2014.
2. ↑ ^{a b c d e} Entry on silver bromide in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
3. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Inorganic Compounds, pp. 4-88.
4. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-4.
5. ↑ C. Doelter, H. Leitmeier: Haloid salts, fluorides, organic compounds (coal, asphalt, petroleum), supplements, general register (final volume) . Springer-Verlag, 2013, ISBN 978-3-642-49884-8 , pp. 72 ( limited preview in Google Book search).
6. ^ ^{A b c} Egon Wiberg: Inorganic Chemistry . Walter de Gruyter, 1952, ISBN 978-3-11-143954-9 , pp. 442 ( limited preview in Google Book search).
7. ↑ ^{a b c} Rudolf Keim: Silver Part B 2. Compounds with bromine, iodine and astatine . Springer-Verlag, 2013, ISBN 978-3-662-13330-9 , pp. 94 ( limited preview in Google Book search).
8. ↑ RW BERRIMAN, RH HERZ: Twinning and the Tabular Growth of Silver Bromide Crystals. In: Nature. 180, 1957, p. 293, doi : 10.1038 / 180293a0 .