A method to detect the effective refractive index and concentration of birefringent pigments is suggested. The method is based on the utilization of the immersion liquid method and a multifunction spectrophotometer for the measurement of back scattered light. The method has applications in the measurement of the effective refractive index of pigments that are used, e.g., in the paper industry to improve the opacity of paper products.
Ilpo Niskanen, Jukka Räty, and Kai-Erik Peiponen, "Estimation of Effective Refractive Index of Birefringent Particles Using a Combination of the Immersion Liquid Method and Light Scattering," Appl. Spectrosc. 62, 399-401 (2008)