https://doi.org/10.1351/goldbook.10210
Apparatus for extraction based on a multistage countercurrent distribution.
Note: The Craig CCD apparatus consists of a battery of glass vessels designed to allow the mixing, settling, and transfer of extracted phase (sample) and the addition of fresh solvent (extractant) in a repetitive fashion. Movement about the horizontal axis provides gentle mixing of the phases, settling, and decanting of the upper phase. The extraction process is slow but is fully automated.