Observation of Spinodal Decomposition in a Hypercompressible Fluid under Reduced Gravity

Phase separation of CO 2 near its critical point is investigated by optical means. In order to prevent the usual strong gravity-driven flows that overwhelm the process, the experiment is performed under reduced gravity. A pattern of interconnected domains of vapour and liquid is observed whose typical scaled wavelength evolves as in density-matched critical binary liquids. In addition, rapid density fluctuations are observed whose origin is unclear.