Cesium phase diagrams

Although prewetting transitions are inextricably connected with first-order wetting transitions, they have proven very difficult to observe experimentally for solid-vapor interfaces. The few systems for which the phenomenon has been observed include He films on cesium (Rutledge and Taborek, 1992), H2 films on rubidium (Cheng et al., 1993), mercury films on sapphire (Hensel and Yao, 1994 Yao and Hensel, 1996), and mercury films on niobium (Kozhevnikov et al., 1997). In these cases, complete prewetting phase diagrams were determined. 

Figure 14.6. Phase diagrams of lyotropic mixtures (temperature versus amphiphile concentration), (a) Hexadecyltrimethylammonium bromide (CTAB)/water, after [50]. L isotropic micellar solution hexagonal phase V bicontinuous cubic phase L lamellar phase C several heterophasic regions containing crystalline components Nc nematic phase of rod-like micelles, (b) Cesium pentadecafluorooctanoate (CsPFO)/water, after [8].

As with azeotropes, eutectics maybe ternary, quaternary, and so on, but their phase diagrams get very complex very quickly. A few important eutectics have an impact on ordinary life. Ordinary solder is a eutectic of tin and lead (63% and 37%, respectively) that melts at 183 C, whereas the melting points of tin and lead are 232 C and 327 C. Wood s metal is an alloy of bismuth, lead, tin, and cadmium (50 25 12.5 12.5) that melts at 70 C (lower than the boiling point of water ) that can be used in overhead fire sprinkler systems. NaCl and H2O make a eutectic that melts at — 21 C, which should be of some interest to communities that use salt on icy roads in the winter. (The composition of this eutectic is about 23 weight percent NaCl.) An unusual eutectic exists for cesium and potassium. In a 77 23 ratio, this eutectic melts at —48 C This eutectic would be a liquid metal at most terrestrial temperatures (and be very reactive toward water). 

Boden et al. [149] used Cs -NMR spectroscopy for mapping phase diagrams of the cesium pentadecafluorooctanoate (CsPF0)/H20 systems. Furo and Sitnikov [150] investigated cesium perfluorooctanoate micelles by F-decoupled C-NMR relaxation rate measurements at three different magnetic fields. 

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