Abstract: A device for mixing of liquids and particulate solids, such as for instance a drilling liquid and drill cuttings on a drilling location. This drilling location can be a deep well drilled for gas and/or oil by means of a drilling tower on-or off-shore. The invention provides an elongated, rectangular open mixing tank (2,3,4,5) on which a series of replacable agitating units (6a, 6b) having their axes (22a, 22b) in one vertical plane is mounted. The agitating devices (6a, 6b) each comprise a unit having a rotatably driven head (21a, 21b) carrying two support arms (23a, 23b; 24a, 24b) of unequal length which each support a mixing screw (27a, 27b, 28a, 28b) projecting into the mixture of liquids and particulate solids. This arrangement provides a thorough mixture of the drilling liquid, having a high viscosity and high specific gravity, with the drill cuttings frequently comprising heavy clay and/or rock particles.