Potassium bromide
[CAS 7758-02-3]

Identification

• Classification: API >> Nervous system medication >> Sedative and hypnotics
• Name: Potassium bromide
• Molecular Formula: KBr
• Molecular Weight: 119.00
• CAS Registry Number: 7758-02-3
• EC Number: 231-830-3
• SMILES: [K+].[Br-]

Properties

• Density: 2.75 g/mL (Expl.)
• Melting point: 734 °C (Expl.)
• Boiling point: 1435 °C (Expl.)
• Solubility: water: 104% w/w (100 °C), slightly soluble in ethanol (Expl.)
• Refraction index: 1.559 (Expl.)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319-H335
• Safety Statements: P261-P264-P264+P265-P271-P280-P302+P352-P304+P340-P305+P351+P338-P319-P321-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Specific target organ toxicity - single exposure	STOT SE	3	H336
Serious eye damage	Eye Dam.	1	H318
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Substances or mixtures which in contact with water emit flammable gases	Water-react.	1	H260
Acute toxicity	Acute Tox.	4	H302
Skin sensitization	Skin Sens.	1	H317
Eye irritation	Eye Irrit.	2A	H319
Specific target organ toxicity - single exposure	STOT SE	1	H371

chemBlink Chemical Story

Potassium bromide, CAS 7758-02-3, is the simple ionic salt KBr. PubChem records a molecular weight of 119.00 and describes it as colorless crystals or a white crystalline powder. Its chemical simplicity contrasts with an unusually broad history spanning nineteenth-century medicine, photographic chemistry and modern infrared spectroscopy.

Bromide salts entered medicine in the nineteenth century and became early effective anticonvulsants and sedatives. Potassium bromide was widely used before newer drugs replaced bromides in most human therapy because prolonged exposure can produce bromism and other adverse effects. Bromide nevertheless retains veterinary importance in some settings, particularly as an anticonvulsant for dogs under professional supervision.

In photography, potassium bromide can provide bromide ion for formation and control of light-sensitive silver bromide. Silver bromide photochemistry was fundamental to traditional photographic plates and films, making a simple soluble bromide salt part of the technological history of imaging.

KBr also has a distinctive analytical role because crystalline potassium bromide transmits much of the mid-infrared region. Finely divided solid samples have historically been dispersed in KBr and pressed into transparent pellets for infrared spectroscopy. This became one of the classic sample-preparation techniques of analytical chemistry, although modern ATR accessories often reduce the need for pellet preparation.

These roles exploit different properties: physiological bromide ion in medicine, precipitation of photosensitive AgBr in photography, and infrared transparency of the KBr crystal lattice in spectroscopy.

References:
1. PubChem, Potassium bromide, CID 253877, CAS 7758-02-3.
2. Sneader W. Drug Discovery: A History. Wiley, 2005.
3. Griffiths PR, de Haseth JA. Fourier Transform Infrared Spectrometry. 2nd ed. Wiley, 2007.

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