In the theoretical part of this dissertation theintroduction of the thermodynamics of mixtures is followed by the basicknowledge of lightscattering. The correlation between thermodynamics atthe one hand and lightscattering at the other is demonstrated. In the apparativeand practicel part the development, build and handeling of the high pressurecell and the carrying out of the light scattering experiments are shown.In the part "results and discussion" the interesting and partly surprisingresults are presentet and discussed