Rate constants and product branching ratios for reactions involving atmospherically interesting ions and ClONO2 have been measured. H3O+ reacts rapidly with ClONO2, but hydrates of H3O+ do not. This implies that ClONO2 does not play a central role in the positive ion chemistry of the atmosphere. CO-3 reacts with ClONO2 to form NO-3. Both NO-3 and NO-3(H2O) react with ClONO2 to form NO-3 (ClONO2). H2O does not react with NO-3(CIONO2, which is essential to the proposed in situ measurement technique. NO-3 (ClONO2) does react with HNO3 and HCl, producing NO-3 (HNO3) in both cases. The reaction of NO-3(HCl) with ClONO2 also produces NO-3(HNO3). These latter two efficient reactions, which are discussed in detail in a separate publication, are analogous to the efficient neutral heterogeneous reaction of HCl with ClONO2 which is important in the chemistry of the Antarctic stratosphere. A detection scheme is presented for atmospheric ClONO2 based on the reactions studied and utilizing mass spectrometry. A ClONO2 detection limit of 107 molecules cm-3 is estimated based on the operating characteristics of current ion-molecule based mass spectrometric field instruments. ¿ American Geophysical Union 1994