Extraction is a technique used for separating a compound from a mixture. An example is separating a water-insoluble organic compound from an aqueous mixture by extracting it into a water-insoluble organic solvent. These extractions are often part of the workup procedure for isolating and purifying the product of an organic reaction. Because trace amounts of water are often present at the end of an extraction process, a drying reagent is needed to ensure a dry product. The process of liquid-liquid extraction involves the distribution of a compound between two solvents that are insoluble in each other. By taking advantage of the differing solubilities of a solute in a pair of solvents, compounds can be selectively transported from one liquid phase to the other.

This occurrence is quantified by the partition coefficient (K):
\text{ K} = \frac{\text{ Concentration of solute in organic phase}}{\text{ Concentration of solute in aqueousphase}}.
The larger the value of K, the solute will be found in greater amounts in the organic solvent. In an extraction procedure, an aqueous phase, usually water, and a immiscible organic solvent known as the organic phase are generally shaken in a container. The solutes are then allowed to distribute themselves between the two layers according to their solubility, the denser layer is always on the bottom of the container. After they have distributed themselves, each layer can be removed and analyzed separately by drying the extractions. The factors that need to be considered in selecting a drying agent are its capacity for removing water, its efficiency, the speed with which it works, and its chemical inertness. Once the extraction has been dried, the solvent must be removed to recover the desired organic product. This can be achieved by heating the container of the mixture and allowing for the solvent to evaporate, leaving a solid or