The objective of this study was to obtain estimates for the refractive indi
ces of bitumen, maltenes, and asphaltenes. Refractive index measurements pe
rformed on various bitumen-solvent mixtures were analyzed using a mixing mo
del that related the refractive index of an ideal mixture to the refractive
indices of the pure components of the mixture. Measurements could only be
obtained for bitumen-solvent mixtures ranging in bitumen volume fraction fr
om 0 to about 0.50. Extrapolation to a volume fraction of unity provided es
timates of 1.584, 1.571 and 1.708 for the refractive indices of bitumen, ma
ltenes, and asphaltenes, respectively. A precipitating solvent was also use
d to show that the onset of asphaltene precipitation could be detected from
refractive index measurements. For a mixture of heptane and bitumen, the o
nset of asphaltene precipitation appeared to occur at a bitumen volume frac
tion of about 0.32. (C) 2001 Elsevier Science Ltd. All rights reserved.