Temperature coefficients of the refractive index for hydrocarbons and binary mixtures

Abstract Temperature coefficients of the refractive index ( dn/dT ) for nine hydrocarbons and two sets of binary mixtures were investigated in this work. The measured − dn/dT values for the pure hydrocarbons were found to be inversely proportional to their molar volumes ( V m ) and molecular weights ( M ). Experimental data for binary mixtures show that − dn/dT varies linearly with volume and mass fractions, consistent with theory derived from the linear relationships of − dn/dT with 1/ V m and 1/ M for individual hydrocarbons. This study should aid the interpretation of the observed correlations of dn/dT with physical and combustion properties of diesel fuels.