On the refractive index of rutile

There are several reports on the measurement of the refractive indices of single-crystal rutile. Whereas the ordinary refractive indices estimated are in close agreement over a wide range of wavelengths, there is a significant difference in the corresponding values of the extraordinary refractive indices. Observations on the ‘prism-coupling technique’ using rutile prisms are reported to show that, for the refractive indices of rutile, the work of W.H. Bond represents a better standard.