Oleum

Oleum

Oleum, also known as fuming sulfuric acid, is a solution of various compositions of sulfur trioxide (SO₃) in sulfuric acid (H₂SO₄). It is a highly corrosive and dense liquid that is used in various industrial processes, particularly in the production of chemicals and explosives.

Chemical Composition

Oleum is represented by the formula H₂SO₄·xSO₃, where x denotes the molar amount of sulfur trioxide dissolved in sulfuric acid. The concentration of SO₃ can vary, leading to different grades of oleum, such as 20% oleum, 40% oleum, etc., where the percentage indicates the amount of free SO₃.

Properties

Oleum is a colorless to slightly yellowish liquid with a pungent odor. It is highly hygroscopic and reacts violently with water, releasing heat and forming sulfuric acid. The presence of free SO₃ makes oleum more reactive than sulfuric acid alone.

Physical Properties

- Density: Oleum is denser than water, with a density that increases with the concentration of SO₃. - Boiling Point: The boiling point of oleum is higher than that of pure sulfuric acid due to the presence of SO₃. - Viscosity: Oleum is more viscous than sulfuric acid, and its viscosity increases with the concentration of SO₃.

Chemical Properties

- Reactivity: Oleum is a powerful dehydrating agent and can cause severe burns upon contact with skin. - Acidity: It is a strong acid, capable of protonating even weak bases.

Production

Oleum is produced by dissolving sulfur trioxide in concentrated sulfuric acid. The sulfur trioxide is typically obtained by the catalytic oxidation of sulfur dioxide (SO₂) in the presence of a vanadium(V) oxide catalyst, a process known as the contact process.

Applications

Oleum is used in various industrial applications, including: - Sulfonation: It is used in the sulfonation of organic compounds, which is a key step in the production of detergents and dyes. - Explosives Manufacturing: Oleum is used in the production of nitroglycerin and other explosives. - Chemical Synthesis: It serves as a reagent in the synthesis of various chemicals, including pharmaceuticals.

Safety and Handling

Due to its corrosive nature, oleum must be handled with extreme care. Appropriate personal protective equipment (PPE) such as gloves, goggles, and acid-resistant clothing should be worn. In case of contact with skin or eyes, immediate flushing with water is necessary.

Environmental Impact

Oleum can cause significant environmental damage if released into the environment. It can lead to acidification of water bodies and soil, harming aquatic and terrestrial life.

Also see

- Sulfuric acid - Sulfur trioxide - Contact process - Acid rain