the jet decks 120 spilling caustic flows onto the sieve section 130 to contact hydrocarbon ascending through perforations in the sieve section 130 caustic that makes it way into the outlet pan 122 of the jet decks 120 proceeds through the inlet 126 of the downcomer 110 down into the inlet pans 132 107 of the subjacent jet deck 120 or feed deck 102 respectively through the outlet 112 this arrangement assures adequate contact between the liquid hydrocarbon and the caustic while the hydrocarbon rises to the top of the once through extraction section 32 and out through the product conduit 60 in a non limiting example embodiment of the present invention the recirculation section 30 of the extraction vessel 24 contains one feed deck and three jet decks 120 and the once through extraction section 32 contains two jet decks 120 the caustic recirculation line 20 is in fluid communication with the inlet pan 132 of the top most jet deck 120 of the recirculation section 30 the fresh or regenerated caustic is in fluid communication with the inlet pan 132 of the upper most jet deck 120 of the once through extraction section 32 of the extraction vessel 24 by the line 50 one advantageous aspect of the invention is that the recirculation of caustic will provide the bulk removal of the mercaptan from the hydrocarbon on the feed deck 102 and jet decks 120 in the recirculation section 30 the final.