Kinetics of phase separation in fluid mixtures by relaxation methods: Pressure-jump experiments and selected results
The investigation of a physico-chemical system in a ñn-eü1librium state as a function of time needs carefully designed experimental methods. The present paper refers to an adaption of relaxation techniques to the investigation of the kinetics of phase separation in fluid mixtures by the use of a fast oressure jump technique. Methods and experimental set-ups are described that allowed us to investigate the transmitted and scattered light intensities as closely as possible to the first formation of droplets after a pressure-jump induced pha— se separation. By evaluation of transient Mie scattering spectra from phase separation processes the existence of a kinetic barrier inside the coexistence region was established and its location inside the phase diagram could be determined. In addition an apparatus for the phenomenological investigation of late stages of phase separation (like aggregation and segregation) with the use of micro and macro photography is described. Recent developments will be reported on applying pressure jump techniques togas-liquidmixtures and improving them to the performance of differential pressure jumps with nearly arbitrary initial and final pressures. Applications on isopycnic systems are discussed in order to simulate the absence of gravitational forces.