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Cover Picture: Osmotic Pressure and Phase Boundary Determination of Multiphase Systems by Analytical Ultracentrifugation (ChemPhysChem 6/2008)
The cover picture illustrates a system of Laponite clay particles, investigated by M. G. Page, H. Cölfen et al. (p. 882) under analytical ultracentrifugation. Separation into its dilute phase, a biphasic isotropic gel and nematic concentrated phase occurs during centrifugation, whilst a laser and detection system mounted on the rotor determines in situ the concentration throughout the sample cell. The plot shows the variation of concentration as a function of radial distance, approaching equilibrium over time. At equilibrium the entire equation of state can be extracted, with both single-biphasic boundary concentrations directly observed, and the osmotic pressure is calculated versus concentration over the entire radial distance.