Abstract: The colloider comprising a collecting tank, the top area of which is suitably designed for receiving the materials, also includes a rotor which is rotatably mounted in the bottom area of the collecting tank and acts as an influence means.To provide a colloider which, for cleaning purposes and repair as well as for material supply and discharge, has a well accessible collecting tank interior and the space requirements and weight of which are low, the colloider comprises a rotor drive shaft which is passed through the bottom of the collecting tank including an opening adapted to be closed by means of a cover and provided in the top area of the collecting tank and is optionally movable into an operating position with the opening being at the top, and into a draining position, with the opening being at the bottom then.