Sulfuric acid (H2SO4), also called oil of vitriol, or hydrogen sulfate, is a dense, colourless, oily, corrosive liquid; one of the most important of all chemicals, prepared industrially by the reaction of water with sulfur trioxide, which in turn is made by chemical combination of sulfur dioxide and oxygen. In various concentrations the acid is used in the manufacture of fertilizers, pigments, dyes, drugs, explosives, detergents, and inorganic salts and acids, as well as in petroleum refining and metallurgical processes. In one of its most familiar applications, sulfuric acid serves as the electrolyte in lead-acid storage batteries.
Sulfuric acid is a very strong acid; in aqueous solutions it ionizes completely to form hydronium ions and hydrogen sulfate ions. In dilute solutions the hydrogen sulfate ions also dissociate, forming more hydronium ions and sulfate ions. In addition to being an oxidizing agent, reacting readily at high temperatures with many metals, carbon, sulfur, and other substances, concentrated sulfuric acid is also a strong dehydrating agent, combining violently with water; in this capacity, it chars many organic materials, such as wood, paper, or sugar, leaving a carbonaceous residue.
Excerpt from the Encyclopedia Britannica without permission.