KCl and NaCl in model steam have been studied by molecular dynamics. The distribution of H2O around the ions has been established and their orientation compared to that predicted for point dipoles. Residual chemical potentials for the ionic species in steam have been calculated from the results of the simulations using the Kirkwood coupling parameter method. With this information it has been possible to calculate the association constant of ions into pairs and the solubility of the solid salts in steam. The results are in a good agreement with the scarce experimental information available. Thermodynamic quantities for ions in steam are compared with those for the hydration of the same ions in water at different temperatures.