Method and apparatus for making acetic acid with improved purification

An improved method of producing acetic acid includes condensing overhead vapor from a light ends column and decanting the condensed vapor to a light phase and a heavy phase. The heavy phase consists predominantly of methyl iodide and at least a portion of the decanted heavy phase is refluxed to the light ends column. Acetic acid content of the light ends column overhead stream and water content of the light ends column product (sidedraw) stream are both decreased, improving purification efficiency.