Experimental methods of studying the fluctuations of the refractive index of binary mixtures of methanol and water

The refractive index of aqueous binary mixtures of water and methanol was studied over the temperature range of 0-80 °C to elaborate the temperature dependence of the molecular dynamics of the systems. In addition to the temperature effects on the index of refraction, the systems were perturbed by gases at pressures from one to three atmospheres for a wide range of concentration to study intra-/inter-molecular forces. These tests were made using a modified Michelson interferometer with a He-Ne laser beam as the light source and a video camera to record the time, temperature and the evolution of the fringes with time. The nature of the solvent-solute interactions was studied through changes that were found in the index of refraction as the temperature or external gas pressure of the system was cycled. Both increasing and decreasing temperature and pressure effects were investigated to test for symmetry. This technique appears to be a highly sensitive method for determining the transport properties and molecular dynamics of the liquids as they interact with laser light