device 2 for instance in the form of a centrifugal pump and a flotation cell 4 connected by a feed line 3 to the pump device 2 for separating metal containing valuable substances from a mass flow such as an ore containing pulp or the like containing metal containing valuable substances a jet device 5 in the sense of an ejector is connected upstream of the flotation cell 4 via which jet device 5 the mass flow is fed tangentially into the flotation cell 4 the feed line 3 ends in the jet device 5 a first blowing device 6 for blowing cf arrow 7 a gas i e in particular air or nitrogen into the feed line 3 is arranged between the pump device 2 which pressurizes the mass flow and the jet device 5 the gas fed into the pressurized mass flow flowing in the feed line 3 allows binding of the optionally hydrophobized metal containing valuable substances so after exiting from the jet device 5 these accumulate in the form of a foam on the surface of the flotation cell 4 and can be removed at this location cf arrow 8 to allow an optimally long dwell time of the gas fed via the blowing device 6 in the feed line 3 and therefore allow good mixing of the gas with the valuable substance particles contained in the mass flow the blowing device 6 is connected immediately downstream of the pump device 2 this means substantially the entire length of the feed line 3 is available for formation of the gas bubbles or rather mixing of.