Abstract: In a device for the automatic measurement of the settlable solids content of a liquid which includes a light transparent vertical measuring tube, a pump for filling the tube with a liquid and a photoelectric scanning head for finding the position of the boundary layer of the deposited solids, and means for emptying of the tube once it has been filled, the measurement of the settlable solids, which has taken place is facilitated by utilizing a piston within the measuring tube which is adapted to be displaced upward thereby permitting movement of the solids to a detector and easy removal of the liquid once the measurement has been made.