hydrodistillation

Hydrodistillation is a traditional method for extracting volatile plant compounds, especially essential oils, by immersing plant material in water and applying heat. When the water boils, steam penetrates the plant tissue and volatilizes its constituents, which are carried to a condenser. The resulting distillate contains an essential oil phase and an aqueous phase, which are then separated.

In typical hydrodistillation setups, plant material is placed in a boiler or distillation pot with water. The mixture is heated to generate steam, which flows through the material and into a condenser. A Clevenger-type receiver or similar device is often used to collect the oil while allowing the water layer to separate, enabling recovery of the oil and disposal or reuse of the water. The process is commonly used for herbs, spices, and aromatic crops such as lavender, thyme, and citrus peels, though it can be applied to a wide range of material.

Compared with steam distillation, hydrodistillation involves direct contact between plant material and water, which can affect heat exposure and may promote hydrolysis of sensitive components. Temperature is typically near boiling, and distillation times vary. Oils obtained are usually accompanied by some water, requiring phase separation; the resulting hydrosol (or floral water) is a secondary product.

Advantages include simplicity and suitability for material that releases oils only with water assistance; disadvantages include potential hydrolytic changes, emulsions, and lower efficiency for some compounds. Hydrodistillation remains a standard method in essential-oil production and in laboratory extraction.