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.
AgBr(s) + KNO3(aq)