Supercritical fluids can replace conventional solvents such as methanol, ethanol, methylene chloride etc. Because some of the conventional solvents are toxic, efforts are now being made to avoid their use.
An alternative to these solvents is provided especially by supercritical CO₂. Substances dissolve at a much higher rate in supercritical fluids than would normally be expected at a given vapour pressure. CO₂ has proven to be especially well-suited for the extraction of natural substances. The low critical temperature of 31°C allows particularly gentle handling of natural substances. Moreover, CO₂ is not only readily available but may also be obtained at relatively low prices.

• Gentle treatment of temperature-sensitive natural substances
• The products obtained are free of solvent
• Natural substances can be separated without losing their aroma
• Selective separation is possible
• The dissolving characteristics of the solvent can be varied by alterations in pressure and temperature
• Simple recovery of the solvent
• No environmental-pollution problems
• Low-energy solvent recovery because CO₂ has a lower evaporation temperature than most organic solvents
• High-purity extracts can be obtained in just a few process steps
• Further on CO₂ is:

• Physiologically completely harmless
• Germicidal
• Non-inflammable
• No process-handling problems