| Appearance | Colorless to brownish liquid |
| Density | ~1.4 g/cm³ |
| Viscosity | Higher than water (varies) |
| Sulfur Trioxide Content | 20 - 65% |
| Free Sulfur Trioxide | Present (fuming oleum contains excess SO₃) |
| Flash Point | 30 - 60 °C |
| Corrosiveness | Highly corrosive |
| Uses | Sulfonation, production of detergents, and chemical synthesis |
| Storage Conditions | Must be stored in specialized containers |
| Shelf Life | 12 - 24 months |
| Common Variants | Fuming oleum, non-fuming oleum |
| Safety Precautions | Handle with care, use protective equipment |