I study by means of thermodynamic calculations the chemical evolution of solar nebular matter during equilibrium condensation from solar and dust-enriched gas and evaporation into nebular gases. The objectives of this research are to understand the behavior of the elements during condensation and subsequent nebular processes, to infer the degree of physical, chemical, and isotopic heterogeneity in the solar nebula and to determine what components were available in the nebula for accretion into meteorites and planets.