467.    CHAKRAVARTY, K. M., AND SEN, R.  X-Ray Diffraction Studies of a Nickel-Thoria-Kieselguhr Catalyst for Fischer-Tropsch Synthesis.  Nature, vol. 160, 1947, pp. 907-908; British Abs., 1948, A I, p. 155.

                  The presence of a few diffraction lines of kieselguhr on the X-ray diffraction diagram shows that, in the process of depositing Ni on kieselguhr, the structure has undergone a change.  The 2 lines of the kieselguhr shown in the photograph are identified as the strong lines of ferric oxide present in the kieselguhr.  The lines of silica on the kieselguhr are absent in that of the catalyst.  It is concluded from this that during deposition of metallic Ni and Th on the kieselguhr the crystalline portion of silica becomes amorphous, while the structure and the crystallinity of the ferric oxide remain unchanged.  The broadness of the lines indicates, however, that the crystal particles of ferric oxide have disintegrated, yielding crystallites of smaller size.  The change in structure was brought about, not by the heating of the kieselguhr in H₂ during the deposition of Ni and Th, but by the disintegration caused by the decomposition of the carbonates of Ni and Th deposited as an initial step in the preparation of the catalyst.  Ni is present as is Th in crystalline form in these samples.

                 CHAKRAVARTY, P. B.  See abs. 459.