Bromides

A bromide ion is a bromine atom with charge of &minus;1.

Compounds with bromine in formal oxidation state &minus;1 are called bromides. This can include ionic compounds such as caesium bromide or covalent compounds such as sulfur dibromide.

Bromide compounds, especially potassium bromide, were frequently used as sedatives in the 19th and early 20th century. This gave the word "bromide" its colloquial connotation of a boring cliché, a bit of conventional wisdom overused as a sedative.

One can test for a bromide ion by adding dilute nitric acid (HNO3), then silver nitrate (AgNO3). A cream precipitate forms that disappears in concentrated ammonia solution.

Bromide is present in typical seawater (35 PSU) with a concentration of aroud 65 mg/l, which is around 0.2% of all dissolved salts.

Bromide is needed by eosinophils (white blood cells of the granulocyte class, specialised for dealing with multicellular parasites), which use it to generate antiparasitic brominating compounds by the action of esoinophil peroxidase, an enzyme which preferentially uses bromide. . Bromide is also used in hot tubs and spas as a germicidal agent, using the action of an oxidizing agent to generate hypobromite in a similar fashion to the peroxidase in eosinophils.

In some cases, bromide is available in a liquid form at pharmacies. It has been rumoured that bromide can reduce incidence of erections for males (see anaphrodisiac), and this was actually its initial pharmacological use. However, such an action is common to all effective sedatives and not known to be especially particular to bromide.

Examples

 * hydrogen bromide (HBr)
 * sodium bromide (NaBr)
 * potassium bromide (KBr), once a commonly used sedative
 * carbon tetrabromide (CBr4)
 * sulfur dibromide (SBr2)

See category for a bigger list.