Viscosities of binary aqueous mixtures of Acetonitrile (AN) and 1,3-Dimethyl-2-imidazolidinone (Dimethylethyleneurea, DMEU) have been measured at atmospheric pressure and temperatures of 20, 25, 30, 35 and 40°C over the entire concentration region by means of Ubbelohde capillary viscometers, type Oc. For a set of 6 viscometers kinetic energy correction functions (Hagenbach-Couette correction) have been experimentally determined for each viscometer using tridistilled water and commercially available liquids. Further corrections accounted for buoyancy and surface tension. Viscosity measurements were carried out with at least three, usually 5 to 6 viscometers, giving viscosities with an estimated uncertainy of 0.3%. Hydrodynamic volumes were determined from relative viscosity vs. concentration curves by means of the viscosity-B-coefficient and compared to van der Waals volumes calculated using increments for functional groups from the literature. Our data indicate the formation of associated species of DMEU and water. Ber. Bunsenges. Phys. Chem. 98, 927-934 (1994) No. 7 0 VCH Verlagsgesellschaft mbH, 0-69451 Weinheim, 1994 wo5-9021/94/0707-0927 $ 10.00+.25/0

Differential cross section (DCS) measurements are reported for scattering of a He atomic beam by crossed beams of C6H6 and C5H5N. Damping of the DCS diffraction oscillations is used to extract reliable anisotropic intermolecular potentials, applying the infinite order sudden approximation (IOSA). The isotropic average for the HeC6H6 potential has a well depth of 3.06 meV and an interatomic separation of 614 pm, while the HeC5H5N potential has a well depth of 3.19 meV and an interatomic separation of 620 pm.

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Differential cross sections have been measured by scattering He atoms from CFnCl4-n (1≤n≤4) in crossed molecular beams. The damping of the diffraction oscillations was used to extract interaction potentials for these molecules which range from nearly isotropic to rather anisotropic. Macroscopic binary parameters, as second virial coefficients, diffusion coefficients and viscosities were calculated from these potentials