Chemistry:Potassium bromate

Short description: Chemical compound

Potassium bromate

Names
IUPAC name Potassium bromate
Other names Potassium bromate(V) Bromic acid, potassium salt
Identifiers
CAS Number	7758-01-2 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:38211 Y
ChEMBL	ChEMBL2311074
ChemSpider	22852 Y
EC Number	231-829-8
Gmelin Reference	15380
KEGG	C19295 Y
PubChem CID	23673461
RTECS number	EF8725000
UNII	04MB35W6ZA Y
UN number	1484
InChI InChI=1S/BrHO3.K/c2-1(3)4;/h(H,2,3,4);/q;+1/p-1 Y Key: OCATYIAKPYKMPG-UHFFFAOYSA-M Y InChI=1/BrHO3.K/c2-1(3)4;/h(H,2,3,4);/q;+1/p-1 Key: OCATYIAKPYKMPG-REWHXWOFAM
SMILES [K+].[O-]Br(=O)=O
Properties
Chemical formula	KBrO3
Molar mass	167.00 g/mol
Appearance	white crystalline powder
Density	3.27 g/cm³
Melting point	350 °C (662 °F; 623 K)
Boiling point	370 °C (698 °F; 643 K) (decomposes)
Solubility in water	3.1 g/100 mL (0 °C) 6.91 g/100 mL (20 °C) 13.3 g/100 mL (40 °C) 49.7 g/100 mL (100 °C)
Solubility	Insoluble in acetone
Magnetic susceptibility (χ)	−52.6·10−6 cm³/mol
Structure
Crystal structure	hexagonal
Thermochemistry
Std enthalpy of formation (ΔfH⦵298)	−342.5 kJ/mol
Hazards
Safety data sheet	"ICSC 1115". http://www.inchem.org/documents/icsc/icsc/eics1115.htm.
GHS pictograms
GHS Signal word	Danger
GHS hazard statements	H271, H301, H350
GHS precautionary statements	P201, P202, P210, P220, P221, P264, P270, P280, P281, P283, P301+310, P306+360, P308+313, P321, P330, P370+378, P371+380+375, P405, P501
NFPA 704 (fire diamond)	0 3 2 OX
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (median dose)	157 mg/kg (oral, rat)
Related compounds
Other anions	Potassium chlorate Potassium iodate
Other cations	Sodium bromate Calcium bromate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Tracking categories (test):

• SizeSet

Potassium bromate (KBrO₃) is a bromate of potassium and takes the form of white crystals or powder. It is a strong oxidizing agent.

Preparation

Potassium bromate is produced when bromine is passed through a hot solution of potassium hydroxide. This first forms unstable potassium hypobromite, which quickly disproportionates into bromide and bromate:

3 BrO⁻ [math]\displaystyle{ \ \xrightarrow{\mathsf{\ (aq)\;}}\ }[/math] 2 Br⁻ + BrO−3

Electrolysis of potassium bromide solutions will also give bromate. Both processes are analogous to those used in the production of chlorates.

Potassium bromate is readily separated from the potassium bromide present in both methods owing to its much lower solubility; when a solution containing potassium bromate and bromide is cooled to 0°C, nearly all bromate will precipitate, while nearly all of the bromide will stay in solution.

Uses in baking

Potassium bromate is typically used in the United States as a flour improver (E number E924). It acts to strengthen the dough and to allow higher rising. It is an oxidizing agent, and under the right conditions, will be completely reduced to bromide in the baking process. However, if too much is added, or if the bread is not baked long enough or not at a high enough temperature, then a residual amount will remain, which may be harmful if consumed.

Potassium bromate might also be used in the production of malt barley, but under certain safety conditions prescribed by the U.S. Food and Drug Administration (FDA), including labeling standards for the finished malt barley product. It is a very powerful oxidizer (electrode potential [math]\displaystyle{ E^\ominus }[/math] = 1.5 volts, similar to potassium permanganate).

Regulation

In October 2023, California passed a law that banned the manufacture, sale, and distribution of potassium bromate (along with three other additives: brominated vegetable oil, propylparaben, and Red 3). This is the first law in the U.S. to ban it, and will possibly have nationwide effects.

Potassium bromate has been banned from food products in the European Union, Argentina, Brazil, Canada, Nigeria, South Korea, and Peru. It was banned in Sri Lanka in 2001, China in 2005, and India in 2016, but it is allowed in most of the United States. As of May 2023, the U.S. state of New York is considering banning the use of potassium bromate. California plans to ban the use of potassium bromate in food starting in 2027, following a bill signed into law in October 2023.

Potassium bromate is classified as a category 2B carcinogen by the IARC. The FDA allowed the use of bromate before the Delaney clause of the Food, Drug, and Cosmetic Act – which bans potentially carcinogenic substances – went into effect in 1958. However, since 1991, the FDA has urged bakers to voluntarily stop using it but has not mandated a ban and some bakers still use it. In California , a warning label is required when bromated flour is used. Japanese baked goods manufacturers stopped using potassium bromate voluntarily in 1980; however, Yamazaki Baking resumed its use in 2005, claiming it had new production methods to reduce the amount of the chemical which remained in the final product.