Potassium bromate

Structural formula
General
Surname	Potassium bromate
other names	Potassium bromicum
Molecular formula	KBrO 3
Brief description	white, crystalline solid
External identifiers / databases
EC number	231-829-8
ECHA InfoCard	100.028.936
PubChem	23673461
ChemSpider	22852
Wikidata	Q409241
properties
Molar mass	167.01 g mol −1
Physical state	firmly
density	3.27 g cm −3
Melting point	350 ° C
boiling point	Decomposes at 370 ° C
solubility	poor in water (69 g l −1 at 20 ° C); practically insoluble in ethanol ;
safety instructions
H and P phrases	H: 271-301-350
	P: 201-210-221-308 + 310
Toxicological data	157 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 .

Potassium bromate KBrO ₃ is the potassium salt of bromic acid .

properties

Potassium bromate

Potassium Bromate Crystals

Potassium bromate is a white, crystalline powder with a density of 3.27 g / cm ³ . It has a melting point of 350 ° C. At 370 ° C., decomposition takes place with elimination of oxygen . Potassium bromate is soluble in water and almost insoluble in alcohol . The solubility in water increases with increasing temperature.

solubility in water
temperature	in ° C	0	20th	40	60	80	100
solubility	in g / 100 g H ₂ O	3.1	6.9	13.1	22.0	33.9	49.7

Bromates are significantly stronger oxidizing agents than chlorates and some of them already react in aqueous solution, which is why they are more toxic and carcinogenic than chlorates. Mixtures of potassium bromate and flammable substances such as phosphorus or sulfur are highly explosive and sensitive to friction. Potassium bromate releases its oxygen and is reduced to potassium bromide .

Potassium bromate crystallizes in the space group R 3 m (space group no. 160) with the lattice parameters a = 601.1 pm and c = 815.2 pm. In the unit cell contains three formula units . Template: room group / 160

The standard enthalpy of formation of potassium bromate at 298.15 K is ΔH _F⁰ = -361.50 kJ mol ⁻¹ , the free enthalpy of formation is ΔG _F⁰ = -271.2 kJ mol ⁻¹ . The enthalpy of solution is ΔH ⁰_sol = 40.58 kJ mol ⁻¹ . The heat capacity at constant pressure is C _p = 105.2 J · mol ⁻¹ · K ⁻¹ .

Extraction and presentation

The synthesis of potassium bromate is carried out by adding bromine in hot concentrated potassium hydroxide solution . The resulting potassium bromate precipitates out of the solution, while the more easily soluble potassium bromide that is formed at the same time remains in solution.

{\ displaystyle {\ ce {Br2 + 2KOH -> KBr + KOBr + H2O}}}

{\ displaystyle {\ ce {3KOBr -> 2KBr + KBrO3}}}

use

Potassium bromate is used as an oxidizing agent in dimensional analysis ( bromatometry ) as a basic titer substance for the determination of arsenic , antimony and tin . It is also used as a single crystal in piezoelectrics .

Its use as a food additive , E924, has fallen sharply due to bans. But it is z. B. still used as a flour treatment agent in the USA to improve baking behavior.

Individual evidence

↑ ^a ^b Entry on potassium bromate. In: Römpp Online . Georg Thieme Verlag, accessed on December 28, 2014.
↑ ^a ^b ^c ^d ^e data sheet potassium bromate (PDF) from Merck , accessed on January 19, 2011.
↑ ^a ^b Entry on potassium bromate in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
↑ Entry on Potassium bromate in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
↑ ^a ^b D. Yoffe, R. Frim, SD Ukeles, MJ Dagani, HJ Barda, TJ Benya, DC Sanders: Bromine Compounds. In: Ullmann's Encyclopedia of Technical Chemistry . Wiley-VCH Verlag, Weinheim 2013, doi : 10.1002 / 14356007.a04_405.pub2 .
^ DH Templeton, LK Templeton: Tensor X-ray optical properties of the bromate ion. In: Acta Cryst. A41, 1985, pp. 133-142, doi: 10.1107 / S0108767385000277 .
↑ RG Kulkarni, TN Wathore: X-ray determination of lattice parameters and thermal expansion of potassium bromate. In: Journal of Materials Science. 16 (3), 1981, pp. 849-851, doi: 10.1007 / BF00552231 .
↑ JR Masaguer, A. Sousa Alonso, J. Romero, MV Coto: Determination of the enthalpy of formation of potassium bromate. In: The Journal of Chemical Thermodynamics. 8 (6), 1976, pp. 525-528, doi: 10.1016 / 0021-9614 (76) 90025-2 .
↑ ^a ^b CRC Handbook of Chemistry and Physics : STANDARD THERMODYNAMIC PROPERTIES OF CHEMICAL SUBSTANCES ( Memento from February 25, 2015 in the Internet Archive ) (Chapter 5.4)
↑ GE Boyd, F. Vaslow: Heats of Solution and Derived Thermodynamic Properties of Alkali Metal Bromates. In: J. Chem. Eng. Data. 7 (2), 1962, pp. 237-238, doi: 10.1021 / je60013a024 .

[roempp-1] Entry on potassium bromate. In: Römpp Online . Georg Thieme Verlag, accessed on December 28, 2014.

[Merck-2] ↑ ^a ^b ^c ^d ^e data sheet potassium bromate (PDF) from Merck , accessed on January 19, 2011.

[GESTIS-3] Entry on potassium bromate in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .

[CLP_100.028.936-4] Entry on Potassium bromate in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .

[Ullmann-5] D. Yoffe, R. Frim, SD Ukeles, MJ Dagani, HJ Barda, TJ Benya, DC Sanders: Bromine Compounds. In: Ullmann's Encyclopedia of Technical Chemistry . Wiley-VCH Verlag, Weinheim 2013, doi : 10.1002 / 14356007.a04_405.pub2 .

[Templeton-6] DH Templeton, LK Templeton: Tensor X-ray optical properties of the bromate ion. In: Acta Cryst. A41, 1985, pp. 133-142, doi: 10.1107 / S0108767385000277 .

[Kulkarni-7] RG Kulkarni, TN Wathore: X-ray determination of lattice parameters and thermal expansion of potassium bromate. In: Journal of Materials Science. 16 (3), 1981, pp. 849-851, doi: 10.1007 / BF00552231 .

[Masaguer-8] JR Masaguer, A. Sousa Alonso, J. Romero, MV Coto: Determination of the enthalpy of formation of potassium bromate. In: The Journal of Chemical Thermodynamics. 8 (6), 1976, pp. 525-528, doi: 10.1016 / 0021-9614 (76) 90025-2 .

[Std-9] CRC Handbook of Chemistry and Physics : STANDARD THERMODYNAMIC PROPERTIES OF CHEMICAL SUBSTANCES ( Memento from February 25, 2015 in the Internet Archive ) (Chapter 5.4)

[Boyd-10] GE Boyd, F. Vaslow: Heats of Solution and Derived Thermodynamic Properties of Alkali Metal Bromates. In: J. Chem. Eng. Data. 7 (2), 1962, pp. 237-238, doi: 10.1021 / je60013a024 .