Positive ion spectra obtained from measurements with a balloon-borne mass spectrometer during three balloon flights are critically investigated and compared with other data. Ion abundances for proton hydrates [H+(H2O)n ions] at different stratospheric temperatures are compared, as well as the abundances of non proton hydrates H+Xitl(H2O)m, X being most likely CH3CN. The detection of trace gases from ion composition measurements is discussed and an upper limit for the number densities of minor constituents such as NH3 and CH3OH is estimated at 35 km. Although sodium compounds cannot be responsible for the major positive ions, a closer investigation of high resolution daytime spectra suggests a small contribution of sodium in daytime ion chemistry.