Abstract: A machine is disclosed for separating solids from feed liquor by gravity settling to form thickened subnatant. The machine includes a liquid-holding tank having an upstanding tubular column mounted therein for receiving the feed liquor. An inlet is formed in the upper portion of the column to admit clarified supernatant into the column for mixing with, and dilution of, the feed liquor. A plurality of subadjacent compartments include reagent introduction and mixing means to receive the feed liquor and to mix a chemical flocculating reagent thereinto. At the bottom of the column is an outlet to discharge the flocculated liquor directly into a pulp blanket stratum established within the tank.