The compounds BaCa0.3Nb0.6Nd0.1O3-delta, SrCa(1+x)/3Nb(2-x)/3O3-x/2 with x = 0.24 and Sr(Zr0.8Ce0.2)(0.8)In0.2O3-delta were analyzed by thermogravimetry regarding their water uptake capacity. Solution enthalpies, entropies and maximum proton contents were extracted from the data. The compounds were also characterized by XRD. As expected, all compounds absorb water vapor and may be expected to show high-temperature proton conductivity. The first compound is derived from the complex perovskite BCN18 introduced by Nowick et al., the second one is the complex perovskite designated SCN24 by the same authors and the third is a new compound with partial substitution of Zr by Ce and trivalent doping.