28 PRACTICAL ORGANIC CHEMISTRY Experiment 6. Fractional Distillation of a Mixture of Benzene and Toluene. Fractionally distil about 40 ml. of a mixture of equal volumes of benzene and toluene, using the type of fractionating column shown in Fig. i I(B), in which about 18-20 cm. of the column are actually filled with glass sections, but in which the cotton-wool lagging is not used. Distil very slowly, so that the total distillation occupies about i£ hours. Shield the apparatus very carefully from draughts. Collect the fractions having the b.ps (a) 80-85°, (^) 85-107°, (c] 107-111°. A sharp separation should be obtained, e.g., these fractions should have volumes of about 19, 2, and 17 ml. respectively. It will be found that the first few drops of the lowest fraction are always cloudy, owing mainly to the fine film of water adsorbed on the glass surfaces within the column. Distillation under Reduced Pressure. Occasionally a liquid, when distillation is attempted under atmospheric pressure,
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.