Many ions that are of paramount importance in solution chemistry could not be produced in the gas phase until the advent of electrospray. The doubly charged ions SO42-.nH(2)O (sulfate), S2O62-.nH(2)O (dithionate) and S2O82-.nH(2)O (peroxydisulfate) were produced in the gas phase by electrospray of solutions containing the disodium salts. The ions were detected with a triple quadrupole mass spectrometer. The primary gas phase ion species selected with Q(1) can be subjected to collision induced dissociation (CID) in Q(2) and the products detected with Q(3). CID of SO42-.nH(2)O led to loss of H2O down to n approximate to 3. For n < 3 an intramolecular proton transfer from HOH to SO42- led to the products HSO4(-) and OH-. The naked SO42- ion could not be detected and could be unstable in the gas phase. CID of the S2O62-.nH(2)O and S2O82-.nH(2)O led to loss of H2O down to the naked ions. The greater stability of S2O62- and S2O82- is expected because of the more extensive charge dispersal possible for these species. CID of S2O82- led to the singly charged species SO4-, SO5-, and SO3-.