Clevenger

A Clevenger apparatus is a piece of laboratory glassware used for continuous extraction of volatile oils or other organic compounds from solid or semi-solid materials via steam distillation. It is primarily employed in the determination of the essential oil content of plant material, particularly herbs and spices.

The apparatus consists of a flask where the sample and water are boiled, a condenser that cools the resulting vapor, and a graduated receiving tube where the oil separates from the condensed water. The specific gravity difference between water and the oil allows for a distinct separation, with either the oil floating on top of the water or sinking to the bottom, depending on its density. A return arm allows the water to flow back into the boiling flask, enabling continuous distillation and extraction.

Variations in the design of the Clevenger apparatus exist, catering to oils that are heavier or lighter than water. These modifications primarily affect the location of the return arm and the graduated section, facilitating efficient separation and accurate volume measurement of the extracted oil. The choice of apparatus depends on the specific properties of the target oil. The method is widely recognized and standardized in pharmacopoeias and other regulatory guidelines for quality control of herbal products.