Measurement of refractive index in liquid mixtures using interferometry

The main parameters that govern the changes in the speed of light when interacting with matter are polarizability and electronic density. The first relates to the ability of a group of atoms to deform under the action of an electromagnetic field, while the second is directly linked to the mass of the substance. If a beam of reference light and another that is incident in the medium whit molecular variation are superimposed, they will be producing a pattern of interference fringes by the phase shift. In this paper we report the results obtained in the measurement of the change in refractive index of liquids substances using patterns of interference fringes. To check the applicability of the technique, two mixtures of different liquid substances were used in the experiment. Water and gasoline were used as solvents and ethanol and gasoline additive were used as solutes, each at different percentages. The results suggest that it is feasible to analyze the variation of the concentration, density and change of refractive index of a substance, through the direct relationship between the molecular changes of the substance analyzed and the phase difference.