Methods have been developed for the isolation and identification of the thiophenes in a Colorado shale-oil naphtha. The basic method for the isolation of thiiophenes from a shale oil naphtha is as follows: 1. Treatment with 10 percent sodium hydroxide. 2. Treatment with 10 percent sulfuric acid 3. Fractional distillation of the neutral naphtha 4. Pentane solution of selected fractions from activated florisil, yielding an aromatic hydrocarbon-thiophene concentrate. 5. Mercuric acetate reaction with the thiophene in the concentrate. 6. Regeneration of the thiophene from the mercuric acetate derivatives. Methods used for the identification of the isolated thiophenes are as follows: 1. Analysis by the mass spectrometer 2. Formation of mercuric acetate and mercuric chloride derivation 3. Hydrogenation to the corresponding paraffin's, and identification of the resulting paraffin's by mass spectra.