978.    FISCHER, F., AND DILTHEY, P.  [Preparation of Pure Carbon at Low Temperatures.]  Brennstoff-Chem., vol. 8, 1927, pp. 388-391; vol. 9, 1928, pp. 24-30; Ges. Abhandl. Kenntnis Kohle, vol. 8, 1929, pp. 234-255; Chem. Abs., vol. 22, 1928, p. 2641.

     C is prepared by passing CO with H₂ (abs. 3580) over reduced alkalized Fe₂O₃ at temperatures around 500°.  The catalyst is prepared by moistening 10 gm. Fe₂O₃ with 1 cc. water glass +15 cc. H₂O and painting this on an Fe spiral made from a strip of Knepp soft sheet 70 x 4 cm.  This was heated in an Al retort similar to that used for low-temperature assay of coal, the preheated supply gas passing in at the bottom and out at the top of the retort chamber.  A contact mass of this size, active Fe 6.8 gm. Fe₂O₃, will take gas at about 40 1./hr. and give 47% of the theoretical yield of C.  The yield falls off in time, possibly because of conversion of active Fe₃C into higher inactive carbides.  S is a contact poison; both the gas and Fe used must be free from S.  A used contact mass could be repeatedly regenerated by dipping into 5 N KOH.  The optimum temperature for CO reduction was 480°-490°, and the optimum ratio CO:H₂=3:1.  An apparatus is shown for moderately large-scale work in which the C formed can be renewed continuously.  The form of C recovered was investigated by X-ray and chemical methods, but no definite conclusion was reached.  Its reactivity was found to be high.  This, however, diminished on removal of Fe.