similar action on the lower fluid is the installation of a second baffle 21 below the tip of suction tube 2b this forms a second annular passageway 2d the action of this second baffle 21 is to prevent flow stream q 2 from disturbing fluid ii as was previously described this fluid enters the inner suction tube 2b from the side and at a distance 34 a 34 from the first baffle 2k the arrangement of choice is to set the distance 34 a 34 smaller than would be possible if no baffle were used as this increases the yield of fluid i fig5 shows a further modification of the practice of this invention in which cleaning solution iii and also inert gas iv may be introduced into container 1 for this purpose the outer suction tube 2a is ringed by a delivery tube 2e which has outlets 2i the delivery tube 2e may be connected to a supply tube 16 for conveying cleaning solutions or to a supply tube 17 for conveying inert gas when used for cleaning the cleaning solution iii travels through supply tube 16 and a pump for cleaning solutions 15 and into the delivery tube 2e and then through outlets 2i to flood the inner surface of the container the cleaning solution iii then collects in the bottom of the container 1 and is next drawn up out of the container 1 through apparatus.