Potassium bromate

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 (Jmol)	Interactive image
ChEBI	CHEBI:38211 Y
ChemSpider	22852 Y
ECHA InfoCard	100.028.936
EC Number	231-829-8
E number	E924 (glazing agents, ...)
KEGG	C19295 N
PubChem	23673461
RTECS number	EF8725000
UNII	04MB35W6ZA N
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	slightly soluble in alcohol insoluble in acetone, ethanol
Structure
Crystal structure	hexagonal
Thermochemistry
Std enthalpy of formation (ΔfHo298)	-342.5 kJ/mol
Hazards
Safety data sheet	ICSC 1115
EU classification (DSD)	Carc. Cat. 2 Toxic (T) Oxidant (O)
R-phrases	R45 R9 R25
S-phrases	S53 S45
NFPA 704	0 2 2 OX
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (median dose)	157 mg/kg (oral, rat)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Potassium bromate (KBrO₃), is a bromate of potassium and takes the form of white crystals or powder.

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:^[2]

3BrO⁻(aq) → 2Br⁻(aq) + BrO−
3(aq)

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.^[2]

Uses in baking

Although banned for use in foods by many countries, in the USA Potassium bromate is typically used 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 used up in the baking bread. 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.^[3] Potassium bromate might also be used in the production of malt barley where the U.S. Food and Drug Administration (FDA) has prescribed certain conditions where it may be used safely, which includes labeling standards for the finished malt barley product.^[4] It is a very powerful oxidizer (E° = 1.5 volts comparable to potassium permanganate).

Regulation

Potassium bromate is classified as a category 2B carcinogen (possibly carcinogenic to humans) by the International Agency for Research on Cancer (IARC).^[5]

Potassium bromate has been banned from use in food products in the European Union, Argentina, Brazil,^[6] Canada, Nigeria, South Korea, Peru and some other countries. It was banned in Sri Lanka in 2001,^[7] China in 2005, and India on 20 June 2016.^[8]

In the United States of America, it has not been banned. The FDA sanctioned 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. But since 1991 the FDA has urged bakers to voluntarily stop using it. In California a warning label is required when bromated flour is used.^[9]

Japanese baked goods manufacturers stopped using potassium bromate voluntarily in 1980; however, Yamazaki Baking resumed its use in 2005, claiming they had new production methods to reduce the amount of the chemical which remained in the final product.^[10]

References