Significant information on the structure of various bisaz.olium salts of the type CA2 (C++ 2A") were revealed by the study of the FAB spectra of their positive and negative ions. Thus only one spectrum, whatever it consists of the positive or of the negative ions spectrum, enables the identification of the cation c++ and of the anion A-. Moreover, the same information are collected from the CAD spectrum of the adduct ion CA+ allowing the identification of such a compound in a mixture.