(592d) Spectroscopic Investigation of Drop Mass Transfer During Buoyancy-Driven Motio

We have developed an experimental setup for looking at real-time concentration measurements of individual drops undergoing mass transfer during buoyancy-driven motion. These experiments are designed to obtain quantitative validation data for numerical models of mass transport and thermodynamics in dynamic systems.  The experimental measurements are accomplished by means of a fiber-optic spectrometer and lens system that focuses a light beam through the moving drop into the detector, where total absorbance is determined.  The system of interest is Neodymium in the aqueous phase complexed by thenoyltrifluoroacetone (Htta) in the organic phase, using xylenol orange as the aqueous metal indicator.  The aqueous phase is buffered to maintain pH throughout the experiment.  A LabVIEW program simultaneously records the spectrometer signal, and the drop location (x,y,z) in the cuvette by means of two CCD cameras.  The advantage of this setup is that transient effects such as the interaction between the drop and the cuvette walls, and the drop and neighboring droplets, can be directly observed.