Abstract: A mixing evaporator is disclosed, of the kind in which a breathable gas mixture is admixed, in the desired proportions, with vapors of an anaesthetic liquid, said gas mixture being compelled to sweep over the liquid level of the anaesthetic to strip vapors therefrom, the improvement consisting in that the gaseous mixture sweeping the anaesthetic liquid is compelled to travel along a sinuous path thereon. The result is obtained by a system of radial paddles having staggered openings so that the gaseous mixture becomes more and more enriched with anaesthetic liquid vapors as it proceeds towards the outlet port.