Vapor pressures were measured for acetonitrile+1-butyl-3-methylimidazolium chloride([C4mim][Cl]),+1-butyl-3-methylimidazolium tetrafluoroborate([C4mim][BF4])and+1-hexyl-3-methylimidazolium chloride([C6mim][Cl])at temperatures of 313 to 353 K by a quasi-static method.The experimental data for the binary systems were correlated by the non-random two liquid(NRTL)equation with an average absolute relative deviation(AARD)of within 1.84%.The results indicate that the three ionic liquids(ILs)can result in a negative deviation from the Raoult's law for the binary solutions containing acetonitrile,and the affinity between ILs and acetonitrile molecules follows the order[C4mim][BF4]+acetonitrile N[C4mim][Cl]+acetonitrile N[C6mim][Cl]+acetonitrile.
