Fluid extract is a type of fluid-solid extraction, that usually employ Soxhlet Apparatus

Soxhlet extractor

A Soxhlet extractor is a piece of laboratory apparatusinvented in 1879 by Franz von Soxhlet. It was originally designed for the extraction of a lipid from a solid material. However, a Soxhlet extractor is not limited to the extraction of lipids...

 to extract certain compound with known solubility in a solvent. Such as extracting lipids from a plant(solid) using ethanol

Ethanol

Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

(liquid). In recent years this has expanded to include specialized extraction methodologies and equipment of a proprietary nature to ratio-intact extract multiple groups of compounds with discovered solubility in a solvent. Such as extracting polysaccharides, resins and organic acids from a plant(solid) using glycerol

Glycerol

Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

(liquid).