The chemical potential of benzene and naphthalene in pure n-alkane fluids at infinite dilution (mu(ex)(infinity)) is calculated using expanded ensemble Monte Carlo simulations. Simulations are carried out in an isobaric-isothermal ensemble at 1 atm pressure. The effect of temperature and carbon number of the solvent on mu(ex)(infinity) is studied. The results indicate that, within the statistical uncertainty of the simulations, there is no strong dependence of the chemical potential of benzene and naphthalene on the carbon number of the solvent between C-6 and C-24. However, the chemical potential changes substantially with the temperature and the size of the solute. Good qualitative agreement is found between the simulation results and experiments.