A major question in the investigation of multiple emulsions of WOW-type is that of stability and ripening, which is often reflected in the droplet-size distribution (DSD). The DSD is an important parameter for judging product properties. Instability in multiple emulsions is often linked to molecular exchange between inner and outer water phases (W 1 , W 2 ), which has to be taken into account. For example, coalescence phenomena and Ostwald ripening affect microscopic and/or macroscopic stability and therefore the multi-dispersity of an emulsion. This is especially important as the inner compartment can act for encapsulating active agents. NMR investigations on emulsions are mainly based on the analysis of diffusion properties of molecules in the different compartments. For determination of the DSD of the inner and outer droplets, it is crucial to know the physical effects influencing the NMR-signal. Depending on these effects, the NMR data are analyzed by different models, depending for example on the occurrence and time scale of molecular exchange between the phases. They are shown to yield correct DSDs. Evidence for the effect of diffusion between phases is given by using the phenomenon of driven diffusion, which allows a direct detection of the exchange by NMR. The exchange is confirmed by confocal laser scanning microscopy.

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Pulsed field gradient NMR (PFG-NMR) is an important method for the characterisation of emulsions. Apart from its application in quality control and process development, especially high-field NMR methods can be applied to investigate emulsions properties on the molecular level. Meanwhile, complex emulsion structures such as double emulsions have been developed and require analytical tools especially for the determination of droplet size distributions. This contribution provides an overview on the possibilities and methods of PFG-NMR referring to measurement, data processing and interpretation of droplet size distributions. Comparison of techniques and measurements on double emulsions are presented.

New working pairs of room-temperature ionic liquids (RTILs) and water offer an opportunity to replace the highly corrosive and partly immiscible working pair of lithium bromide (LiBr) and water in absorption cycles like the absorption chiller. To estimate the suitability of these working pairs, the knowledge of thermophysical properties is inevitable. Due to the lack of literature data the following properties of two RTIL−water mixtures will be presented in this paper. Vapor−liquid equilibria (VLE) of the binary mixture of water + diethylmethylammonium trifluoromethanesulfonate ([DEMA][OTf]) and the ternary mixture of water + [DEMA][OTf] + diethylmethylammonium methanesulfonate ([DEMA][OMs]) were measured in the temperature range T = (293.15 to 353.15) K. The VLE measurements were carried out by Fourier transform infrared (FTIR) spectroscopy in a dynamic cell. The experimental VLE data were fitted with the nonrandom two-liquid (NRTL) model. Heat capacities, densities, and viscosities of the binary mixtures water + [DEMA][OTf] and [DEMA][OTf] + [DEMA][OMs] were measured. The measurements of the heat capacity were conducted via differential scanning calorimetry (DSC) in the temperature range T = (293.15 to 363.15) K. The density was measured with a pycnometer and the viscosity with a falling sphere viscometer. The temperature range for both was T = (293.15 to 353.15) K. Diffusion coefficients of water in the RTILs were determined by pulsed field gradient-nuclear magnetic resonance spectroscopy (PFG-NMR) in the temperature range of T = (288 to 313) K. ■ INTRODUCTIONRoom-temperature ionic liquids (RTILs) are salts which are liquid at room temperature and atmospheric pressure. They are composed of an organic cation and an inorganic or organic anion. Due to the numerous possible combinations of anions and cations, physical and chemical properties can be adapted over a wide range. 1,2 The most preferable properties for industrial applications are a low melting point, a wide liquid range, a negligible vapor pressure, and nonflammability. 3 This leads to a large number of possible applications in synthetic, analytical, and engineering processes. Today RTILs are used for example as extraction agents in separation processes, and they are also suited to replace conventional organic solvents due to their negligible vapor pressure. 3,4 Other fields of application such as the use as lubricants, in electrochemistry, and in bioscience are also being considered. 5,6 This led to an enormous increase of scientific investigations over the past years. 1−18 Our group is investigating new working pairs for the absorption chiller to replace the highly corrosive and partly immiscible but still commonly used working pair LiBr and water. 7,8 The absorption chiller offers the opportunity for ambient cooling by the usage of waste heat or solar energy. A description of the process can be found in literature. 9 The temperature range of the solution cycle in the process is set by the cooling water temperature in the absorber (around 298 K) and...