Nine ionic liqs. were prepd. by reaction of 4-Cl-2-MeC6H3OCH2COONa with quaternary ammonium chlorides or bromides in H2O at 50 degrees C (optionally after preliminary quatemization with C10H21OCH2Cl) (yield 86-98%), and studied for chem. structure (NMR), purity (94-98%), phase transition temps., thermal stability and herbicidal activity. Most liqs. were stable (decompn. below 5%) up to 160-217 degrees C.