Automated measurement of the refractive index of fluids

A method for automating refractive-index measurements of fluids has been developed. An encoded rotation stage and position-sensitive detector enable automated reading of angles typically acquired by visual means. Two tunable lasers are used to obtain index measurements at ten discrete wavelengths across the visible spectrum. This method has been implemented on a Hilger-Chance refractometer from which the bulk refractive-index values for various transparent fluids have been measured. An index measurement accuracy of better than one part in the fourth decimal place for distilled water and a few parts in the fourth decimal place for higher index fluids is obtained.