3360.     ---------------.  [TEICHNER, S.]  [Choice of Role of Kieselguhr as Support of Fischer Catalysts.]  Compt. rend., vol. 228, 1949, pp. 1,644-1,646; Chem. Abs., vol. 43, 1949, p. 8,830.

        Three commercial kieselguhrs -- crude Filter-Cel, acid-treated Filter-Cel, and crude Hyflo-Super-Cel -- were subjected to thermal and alkaline treatment and loss in weight, density, and specific surface were determined.  As the result of such considerations, the reactivity of a kieselguhr may be defined as the % of silica capable of being dissolved warm in a 5% solution of Na₂CO₃, which dissolves the amorphous or very finely divided silica.  The efficiency of the kieselguhr in a Fischer catalyst is linked to the quantity of reactive silica that it initially contains or which it is possible to generate by acid treatment, as well as to the real surface of this reactive silica.  The formation of hydrosilicates with foliated structure can, in fact, be promoted only by this type of silica.