Experimental monitoring techniques droplets

Eressure is determined by the water vapor partial pressure, which is carefully ept at saturation with respect to the equilibrium vapor pressure of water at the droplet temperature so that the droplets neither grow nor evaporate. Depending on the temperature of the droplets this sets the minimum pressure at 4 to 20 Torr. The transit time of the droplets through the reaction zone is short, on the order of a few milliseconds, in order to avoid saturation of the trace gas in the liquids. Experimental parameters are computer monitored. The details of the technique and of the experimental procedures are discussed in reference (2). 

In principle, we can distinguish (for surfactant self-assemblies in general) between a microstructure in which either oil or water forms discrete domains (droplets, micelles) and one in which both form domains that extend over macroscopic distances (Fig. 7a). It appears that there are few techniques that can distinguish between the two principal cases uni- and bicontinuous. The first technique to prove bicontinuity was self-diffusion studies in which oil and water diffusion were monitored over macroscopic distances [35]. It appears that for most surfactant systems, microemulsions can be found where both oil and water diffusion are uninhibited and are only moderately reduced compared to the neat liquids. Quantitative agreement between experimental self-diffusion behavior and Scriven s suggestion of zero mean curvature surfactant monolayers has been demonstrated [36]. Independent experimental proof of bicontinuity has been obtained by cryo-electron microscopy, and neutron diffraction by contrast variation has demonstrated a low mean curvature surfactant film under balanced conditions. The bicontinuous microemulsion structure (Fig. 7b) has attracted considerable interest and has stimulated theoretical work strongly. 

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