Resumen de Sugar Fingers and Double-Diffusive Convection

Richard M. Heavers, Liza A. Colucci

• Vertical convection cells ("fingers") develop at the interface between a horizontal layer of sugar solution above a slightly denser solution of ordinary table salt. These fingers occur primarily because the molecular diffusivity of sugar is less than that of salt. We describe a two- or three-hour laboratory experiment in which the contributions of salt and sugar to the densities of both layers are measured over time with a refractometer and from the rotation of polarized light in a laser beam. Initial densities for salt and sugar solutions are specified for the experiment and for a physical chemistry class demonstration in which the fingers are projected on a screen. An example of undergraduate research is also given.