What is "bromo-seltzer"

Bromo-Seltzer ( acetaminophen, sodium bicarbonate, and citric acid), was a brand of antacid to relieve pain occurring together with heartburn, upset stomach, or acid indigestion. First produced by inventor Isaac E. Emerson's drug company of Baltimore, Maryland, in 1888, Bromo-Seltzer was sold in the United States in the form of effervescent granules which must be mixed with water before ingestion.