3456.     TROPSCH, H., AND DITTRICH, E.  [Analysis of Gaseous Hydrocarbons, Particularly Olefins.]  Brennstoff-Chem., vol. 6, 1925, pp. 169-177; Ges. Abhandl. Kenntnis Kohle, vol. 8, 1929, pp. 285-304; Chem. Abs., vol. 19,1 925, p. 2793.

        Fractional condensation at liquid-air temperatures was applied in the analysis of complex mixtures of paraffins and olefins.  Gases other than hydrocarbons are first determined (CO₂ by adsorption in KOH, O₂ with alkaline pyrogallol, CO with ammoniacal CuCl₂ and H₂ by selective combustion over CuO heated to 240°, at which temperature it is shown the higher hydrocarbons are not affected) and the residual hydrocarbons are then condensed by liquid air in an apparatus built by Ströhlein Co. Düsseldorf.  Condensation and fractionation are carried out in 4 U-tubes cooled to suitable temperatures by liquid air and also by Al blocks cooled by this medium.  The fractionation is carried out under high vacuum maintained by a Töpler pump.  A Gaede pump is used also to circulate gases.  The fractions obtained are:  B (CH₄), C₁ (ethane, propane, ethylene, and propylene), C₂ (propane, butane, propylene, and butylene), D (olefins and paraffins of higher molecular weight).  From the individual fractions, ethylene homologs are absorbed by 87% H₂SO₄ and ethylene itself is absorbed by a mixture of solutions a and b in proportions 0.25:1.875, a being 87% H₂SO₄ saturated with NiSO₄, and b being 87% H₂SO₄ containing 0.6% AgSO₄.  The amount of C corresponding to each vol. absorbed is determined by oxidation of the acid solution with excess KIO₃ and back titration of the excess with Na₂S₂O₃.  Paraffin hydrocarbons are determined by combustion in small quartz tubes containing heated CuO.  Boiling curves of the hydrocarbons are given with numerous tables of analytical data for pure gases.  Specimen analyses of (1) an oil gas, (2) a synthol gas, and (3) a gas from the Bergius hydrogenation process are given.