Abstract: Organopolysiloxane powder is prepared from an organopolysiloxane solution by admitting the organopolysiloxane solution into a planetary-screw mixer and agitating the solution at a sufficient temperature to allow a low-boiling liquid component to evaporate from the solution, thereby separating the low-boiling liquid component from the solution.

Abstract: A simple but very effective and reliable method is proposed for the decolorizing purification of a halogenated silane compound, e.g., methyl trichlorosilane, colored by containing a very small amount of heavy metal impurities such as iron. The method comprises: contacting the halogenated silane compound with a small amount of a cationic surface active agent which is solid and insoluble in the silane such as a quaternary ammonium salt, e.g., trimethyl octadecyl ammonium chloride, for 2 to 240 minutes; and then separating the silane compound from the cationic surface active agent.