NOVELTY - A crude stream comprising vinyl acetate, ethylene and argon is withdrawn, after reaction for production of vinyl acetate. A portion of vinyl acetate is removed, to form a non-product stream (S). S is passed through a membrane selectively permeable to ethylene and an argon-rich purge stream and an ethylene-rich permeate stream (P), are withdrawn. A portion of (P) is recirculated to the reactor.    USE - For treating off-gas streams from the reactor (claimed) to purge argon and other inert gases, without losing large amounts of ethylene reagent.    ADVANTAGE - An improved method that provides a new and advantageous technique for venting excess argon and other contaminants from the reaction loop for production of vinyl acetate, with reduced loss of ethylene, is offered. Vinyl acetate manufacture is improved, and argon is removed from reactor vent streams with minimal corresponding loss of ethylene.    DETAILED DESCRIPTION - Production of vinyl acetate comprises reacting ethylene, acetic acid and oxygen in a reactor (102). A crude product stream (103) comprising vinyl acetate, ethylene and argon is withdrawn and a portion of vinyl acetate is removed to form a non-product stream (106). The non-product stream is passed through a membrane (115) selectively permeable to ethylene over argon and from feed side (116) an argon-rich purge stream is withdrawn, and from permeate side (117) an ethylene-rich permeate stream is withdrawn. A portion of the ethylene-rich permeate stream (112) is recirculated to the reactor. An INDEPENDENT CLAIM is also included for a process for treating a purge stream from vinyl acetate manufacturing process. Purge stream, comprising ethylene and argon is passed through a selectively permeable membrane so as to separate ethylene-rich and argon-rich fractions, from which ethylene-rich permeate stream is recirculated.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of production of vinyl acetate.    Raw feed stream (101)    Reactor (102)    Crude-product stream (103)    Product stream (105)    Non-product gas stream (106)    Combined stream (107)    Compressor (108)    Feed stream to argon removal unit (110)    Feed stream to carbon-dioxide removal unit (111)    Recirculating gas (112)    Carbon-dioxide depleted stream (115)    Membrane separator (113)    Feed side stream (116)    Permeate side stream (117)    Reactor feed stream (119)