Partial condenser 626 INDEX

Selenium monoehloride is a clear reddish-brown liquid of density (D lT) 2-7741, and can be condensed to a solid of melting-point —85° C.7 Its odour somewhat resembles that of sulphur monoehloride. The liquid has a refractive index of 1-59617 at 25° C-, and its specific conductance is 5-12 X10-7 mho. On vaporisation it undergoes partial dissociation. Boiling commences at 145° C., the yellowish-brown vapour containing the tetrachloride and a residue of selenium being obtained in the retort 8... 

The exponent values in expressions (5.2)—(5.5) depend on the particular parameters in the exponent index, but they are usually much larger than the unit at r < 10-50 nm (see Table 5.1). In a homogeneous mother sys tern (free of seeds for the solid phase condensation), the process rate depends on the rate of homogeneous nucleation of the new phase from nonequilibrium (oversaturated) systems. The high partial pressure of the equilibrium vapor or solute over small particles allows the first condensed particles nuclei of the new phase) to form at a considerable oversaturation of the vapor in the initially homogeneous system. 

On this basis, a rapid and nondestructive method, ellipsometric porosimetry (EP), has been developed in which adsorption-desorption isotherms are determined from the variations of film refractive index efr induced by the change of partial pressme of a solvent above a film. The setup combines a pressure-controlled chamber (conventional gas volumetric characterization devices) and a classical eUipsometer thus, HeS is determined for each vapor pressure and is a direct measme of the adsorption isotherm. A typical example is shown in Figure 33.3a for a Si02 templated with CTAB thin film (Martinez Ricci, M.L., Fuertes, M.C., Violi, I.L., Grosso, D., and Soler lUia, G.J.AA., Rational design of mesoporous films for synthesis of responsive Bragg reflectors (unpublished).). The refractive index increases from eff (630 nm) = 1.21, for a large fraction of air inside micropores and/or mesopores within the silica nanostructure, to (630 nm) = 1.37 when pores are saturated with water. The steep increase at intermediate vapor pressures is associated with the capillary condensation inside pores. The hysteresis in the desorption branch is due to the presence of water in the necks that join pores, whose effective radii are smaller than the pore radius. 

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