Interferometric determination of the refractive index of liquid sulphur dioxide

The absolute refractive index of liquid sulphur dioxide (SO₂) was determined with an uncertainty of ±0.0007 with the help of a Michelson interferometer and a computer-controlled rotatory stage supporting a rectangular fused silica cell, containing the liquid. The measurements were performed at temperatures around 20 °C for the laser line wavelengths 632.8, 514.5 and 488.0 nm. The experimental data were fitted to the simple Cauchy dispersion formula. The results calculated from this formula are consistent within the experimental uncertainty with published values obtained at other wavelengths and/or other temperatures.