It is a device that allows the distillation of small quantities of liquids (or low melting point solids), including solvents with low boiling point as well as for drying samples. It is also used to separate polymeric substances or high melting point oils.
The system has a series of glass spheres that are connected together. The balls are rotating and moving at the same time in front of a heat source, and the assembly is connected to a vacuum pump.
The samples can be observed directly and due to the transparency of the glass visualize how they pass from one ball to another (see Figure). When used to dry solid samples it is a substitute for a desiccator.