The objective of this research was to apply the TK!Solver program for thermodynamic calculations. The TK!Solver program is equation-solving software that can solve both linear and non-linear sets of equations. To achieve the above objective, six programs have been developed. Program ESTATE.TK calculates volumetric properties of compounds using the ideal gas law, Pitzer correlation, van der Waals, Redlich-Kwong, Dieterici, or Berthelot equation of state. The volumetric properties include temperature, pressure, volume, and compressibility factor. Program RESIDUAL.TK calculates residual and total properties of compounds as a function of temperature and pressure using the Pitzer correlation, van der Waals, or Redlich-Kwong equation of state. The residual and total properties include residual volume, residual internal energy, residual enthalpy, and residual entropy. Program FRENERGY.TK calculates standard free energy of formation, standard enthalpy of formation, and standard entropy of formation for a compound or a reaction as a function of temperature. This program also calculates the equilibrium constant for a reaction as a function of temperature. Program CHON.TK calculates the equilibrium composition for an adiabatic or non-adiabatic reactor as a function of the temperature and pressure of the reactor, hydrogen-to-oxygen ratio, and nitrogen-to-oxygen ratio in the feed. The feed to the reactor consists of the elements carbon, hydrogen, oxygen, and nitrogen. The products of the reactor are methane, water, carbon monoxide, carbon dioxide, hydrogen, and nitrogen. Program CRITICAL.TK furnishes critical data for more than fifty compounds. The critical data includes critical temperature, critical pressure, critical volume, critical compressibility factor, and the acentric factor. Programs ESTATE.TR and RESIDUAL.TK have access to data file CRITICAL.TK for state property calculations. Program DATBANK1.TK supplies heat capacity data, heat of formation, and entropy of formation data for more than one hundred compounds. Programs RESIDUAL.TK and FRENERGY.TK have access to data file DATBANK1.TK for enthalpy and entropy calculations. These six programs may be considered as a basis for an "expert" system for thermodynamic calculations. Data can be easily added to extend the calculations to include additional compounds. / M.S.