Abstract: The titration of bases and salts in acetic anhydride has been systematically investigated.Using 50% AcOH-(Ac)₂O HClO₄ as a titrant,25 kinds of salts and 28 kinds of bases have been titrated in this solvent by the authors.It is pointed out that for the nonaqueous titration of some weakest bases,e.g.,urea,thiourea,caffeine and acetanilide,etc.and some neutral salts such as sodium camphorsulfonate,etc.,acetic anhydride is an excellent solvent. A serial HNP(half neutralization potentials)of bases and salts have been estimated and arranged according to their relative intensities in order to select a suitable indicator for visual titration.It is concluded that a compound with a HNP below 450 mv can be taken as a visual titration using crystal violet as an indicator.However,those compounds with a HNP vicinal to 650 mv cannot be titrated visually,but often can be titrated potentiometrically. The mixture of bases and salts and those compounds with bifunctional basic groups can be resolved by differentiating titrations,provided the HNP differ from each other by 200 my. Both aliphatic and aromatic primary amines,reacted with acetic anhydride,can be satisfactorily titrated,on the condition that there are no negative radicals existing in molecules which highly decrease in the basicities of amines.