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3 Experimental Methods

The aim of this chapter is to describe the general principles of experimental methods, which have been used in this work. The chapter is divided into four major sections. The first section (3.1) describes the general aspects of experimental set-ups, to optimize the accuracy of measurements. The second Section (3.2) deals with the dynamic light scattering (DLS) theory and experimental set-up while the third Section (3.3), focused on the broadband ultrasonic (US) theory and experimental setup. A fourth Section (3.4) presents the complementary measurement methods, like shear viscosity, density and calorimetry, which have been used to determine useful thermodynamic parameters.

3.1 General aspects

All technical equipment has been operated in temperature controlled ±1 K laboratories. The specimen cells were provided with channels for circulating thermostat fluid and ad- ditionally placed in thermostatic boxes. This kind of thermostatic shielding allows to control the temperature of the measurement cells to within 0.02 K. The temperature was measured with an error less then 0.01 K using Pt 100 thermometers. In order to avoid mechanical stress during the measurements, the DLS and US cells have been placed on massive granite tables. Both species of cells, the light scattering cells (sample volume 2 ml) as well as ultrasonic cells (samples volume between 2 ml and 200 ml) have been subjected to extremely accurate cleaning procedure before use. The light scattering cells have been treated in an ultrasonic bath cleaner, filled with isopropanol, for several hours before starting a series of measurements. Finally, the cells have been dried in a vacuum oven. In the case of ultrasonic cells the cleaning and preparation procedure is somewhat different. The cells have been first flooded continuously with distilled water for several hours. Afterwards remaining water in the cells has been dissolved by methanol and the cell has been dried with the aid of nitrogen gas for about 30 minutes. The filling pro- cedure of the ultrasonic cells has to be likewise done with care. To avoid air bubbles in the cell the substances have to be filled continuously and slowly from the bottom. The aim is to get the best contact between transducer surface and the investigated substance as well as to avoid air bubbles. Consequently, the speed of cell filling is crucial for the proper operation of the transducers. All measurements have been performed at standard pressure.

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