Sulfuric acid, dense, colourless, oily, corrosive liquid; one of the most commercially important of all chemicals. Sulfuric acid formula is prepared industrially by the reaction of water with sulfur trioxide (see sulfur oxide), which in turn is made by chemical combination of sulfur dioxide and oxygen either by the contact process or the chamber process. 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 formula serves as the electrolyte in lead–acid storage batteries.

Pure sulfuric acid formula has a specific gravity of 1.830 at 25 °C (77 °F); it freezes at 10.37 °C (50.7 °F). When heated, the pure acid partially decomposes into water and sulfur trioxide; the latter escapes as a vapour until the concentration of the acid falls to 98.3 percent. This mixture of sulfuric acid and water boils at a constant temperature of 338 °C (640 °F) at one atmosphere pressure. Sulfuric acid formula is commonly supplied at concentrations of 78, 93, or 98 percent.
Due to its affinity for water, pure anhydrous sulfuric acid formula does not exist in nature. Volcanic activity can result in the production of sulfuric acid, depending on the emissions associated with specific volcanoes, and sulfuric acid formula aerosols from an eruption can persist in the stratosphere for many years. These aerosols can then reform into sulfur dioxide (SO2), a constituent of acid rain, though volcanic activity is a relatively minor contributor to acid rainfall.
Sulfuric acid formula is a very strong acid; in aqueous solutions it ionizes completely to form hydronium ions (H3O+) and hydrogen sulfate ions (HSO4−). In dilute solutions the hydrogen sulfate ions also dissociate, forming more hydronium ions and sulfate ions (SO42−). In addition to being an oxidizing agent, reacting readily at high temperatures with many metals, carbon, sulfur, and other substances, concentrated sulfuric acid formula 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.
The term fuming sulfuric acid, or oleum, is applied to solutions of sulfur trioxide in 100 percent sulfuric acid; these solutions, commonly containing 20, 40, or 65 percent sulfur trioxide, are used for the preparation of organic chemicals.
Sulfuric acid formula is a colorless oily liquid. It is soluble in water with release of heat. It is corrosive to metals and tissue. It will char wood and most other organic matter on contact, but is unlikely to cause a fire. Density 15 lb / gal. Long term exposure to low concentrations or short term exposure to high concentrations can result in adverse health effects from inhalation. It is used to make fertilizers and other chemicals, in petroleum refining, in iron and steel production, and for many other uses. Rate of onset: Immediate Persistence: Hours, days Odor threshold: Source/use/other hazard: Battery/dyes/paper/glue/metals industries; volcanic gas; toxic fumes when heated.