Oleum 23, also known as Fuming Sulfuric Acid or Disulfuric Acid, is a highly corrosive and toxic chemical compound with the formula H2S2O7.

Characteristics
1. Composition: Oleum 23 is a mixture of sulfuric acid (H2SO4) and sulfur trioxide (SO3).
2. Appearance: It is a colorless to dark brown, oily liquid with a pungent, choking odor.
3. Corrosivity: Oleum 23 is highly corrosive and can cause severe burns upon contact with skin.

Applications
1. Chemical synthesis: Oleum 23 is used as a reagent in various chemical reactions, such as the production of detergents, pharmaceuticals, and dyes.
2. Sulfonation reactions: It is used as a sulfonating agent in the production of surfactants, detergents, and other chemicals.

Safety and Handling
1. Personal protective equipment (PPE): When handling Oleum 23, it is essential to wear PPE, including gloves, goggles, and a face shield.
2. Ventilation: Adequate ventilation is necessary when working with Oleum 23 to prevent inhalation of the fumes.
3. Storage: Oleum 23 should be stored in a cool, dry, well-ventilated area, away from incompatible materials.