1949. ------. [KRCZIL, F.] [Siliceous Materials.] French Patent 748,584, July 6, 1933. Chem. Abs., vol. 27, 1933, p. 5491.

Siliceous materials, such as kieselguhr, infusorial earth, kaolin, and clay, are purified or regenerated by calcination in the presence of hot gases, which keep the material in a whirl or suspended through the operation. The gases may be inert or chemically active to produce purification.