Hollow fiber gas membranes can rapidly separate acetic acid from liquids. Acetic acid volatilizes from the liquid, diffuses across a gas layer held within the membrane, and is neutralized by a caustic stripping solution. Studies conducted on acetic acid solutions show that the process will work, although the tendency of acetic acid to dimerize can reduce its mass transfer rate. Ethanol and ethyl acetate (a model flavor ester) also migrate across the membranes. The removal of ethanol may be avoided by elevating the alcohol concentration in the caustic stripping solution. The removal of esters is harder to inhibit since these compounds hydrolyze under the caustic conditions.