A SCANNING MICHELSON INTERFEROMETER FOR THE MEASUREMENT OF THE CONCENTRATION AND TEMPERATURE DERIVATIVE OF THE REFRACTIVE-INDEX OF LIQUIDS

A compact scanning Michelson interferometer for the measurement of both the concentration and temperature derivative of the refractive index of liquids, liquid mixtures, and solutions has been developed. Scanning of one of the mirrors allows the extraction of the phase information and makes the instrument insensitive to intensity drifts of the light source. The refractive index noise level of the empty instrument is of the order of 10(-8) for a 10mm sample cell, and for continuously varying refractive indices there is no upper limit of the linear detection range. Accuracies of the order of 0.5% can be achieved both for (partial derivative n/partial derivative c(p,T)) and (partial derivative n/partial derivative T-p,T-c).