Abstract
The ordinary and extraordinary refractive indices in the nematic phase and the refractive index in the isotropic phase of binary mixtures of p-Azoxyphenetole (PAP) with 4,4'-di-n-propyloxyazoxybenzene (PDPAB), with 4,4'-di-n-butyloxyazoxybenzene (PBAB), with 4,4'-di-n-pentyloxyazoxybenzene (PPAB) and with 4,4'-di-n-hexyloxyazoxybenzene (PHAB) are reported. These refractive index data were used in a Vuks type analysis to obtain the values of the order parameters in PAP/PDPAB, PAP/PBAB, PAP/PPAB and PAP/PHAB mixtures. It is found that the order parameters in these four mixtures obey the additive rule.