Abstract: A method for separating the isomers of a crown ether compound and making it possible to recover in particular the pure cis-syn-cis isomer from DCH 18C6 includes:a) dissolving in an organic solvent a mixture of the isomers of said crown compound including the cis-anti-cis isomer and the cis-syn-cis isomer,b) adding uranyl nitrate to the solution obtained in stage a) in sufficient quantities so that virtually all of the isomers, except the cis-syn-cis isomer, are precipitated in the form of complexes with the uranyl nitrate,c) separating the formed precipitate,d) recovering the cis-syn-cis isomer from the solution, ande) recovering the cis-anti-cis isomer from the precipitate.