The dissolution enthalpies of BaCe0.7Ho0.2In0.1O2.85 and BaCe0.7Sm0.2In0.1O2.85 were measured by method of solution calorimetry in 1M hydrochloric acid with adding 0.1 M KI. The obtained data were compared with earlier measured data on dissolution enthalpies of BaCe0.7Nd0.2In0.1O2.85, BaCe0.7Gd0.2In0.1O2.85. The dependence of dissolution enthalpies from lanthanide radius was constructed. As was shown the relationship is not linear.