Abstract: A method for the separation of organic compounds by clathration in which there is used as a host a compound of formula I: ##STR1## wherein: Ar.sup.1 Ar.sup.2 and Ar.sup.3 and Ar.sup.4, which may be identical or different, represent aromatic groups; X and Y, which may be identical or different, represent P, As or Sb or P, As or Sb to which O, S or Se are bound; R represents a bond joining X and Y, a substituted or unsubstituted alkylene group, a substituted or unsubstituted arylene group, a substituted or unsubstituted alkenylene group or a substituted or unsubstituted alkynylene group. The compound of formula I in which Ar.sup.1 -Ar.sup.4 represent phenyl, X and Y each represent P.dbd.Se and R represents --(CH.sub.2).sub.2 -- is particularly useful for the clathration of p-xylene.