In the first step, sulfur is burned to produce sulfur dioxide (SO2). This is then oxidized to sulfur trioxide (SO3) using oxygen in the presence of a vanadium (V) oxide catalyst. This reaction is reversible and the formation of the sulfur trioxide is exothermic.
The sulfur trioxide is absorbed into 97–98 % H2SO4 to form oleum (H2S2O7), also known as fuming sulfuric acid. The oleum is then diluted with water to form concentrated sulfuric acid (H2SO4). Note that directly dissolving SO3 in water is not practical due to the highly exothermic nature of the reaction between sulfur trioxide and water. Instead of a liquid, the reaction forms a corrosive aerosol that is very difficult to separate.
Sulfuric acid has many applications and is a central substance in the chemical industry. Principal uses include lead-acid batteries for cars and other vehicles, mineral processing, fertilizer manufacturing, oil refining, wastewater processing and chemical synthesis.
Sulfuric Acid And Oleum: All With One Instrument
Anton Paar produces the only single sensor capable of measuring the entire range of H2SO4 and oleum! Phosphoric acid is a non-toxic, inorganic, rather weak triprotic acid, which, when pure, is a solid at room temperature and pressure. Phosphoric acid, also known as orthophosphoric acid or phosphoric (V) acid, is a highly polar molecule and therefore highly soluble in water.
Phosphoric acid is commonly used as an aqueous solution of 85 % phosphoric acid or H3PO4. Phosphoric acid may be used as a "rust converter", by direct application to rusted iron, steel tools, or surfaces. The phosphoric acid converts reddish-brown iron (III) oxide, Fe2O3 (rust) to black ferric phosphate, FePO4.