THE PROPERTIES AND BEHAVIOR OF CHEMICAL SYSTEMS WITH COMPONENTS IN MULTIPLE PHASES ARE OFTEN KEYS TO PHYSICOCHEMICAL PROCESSES IN THE ATMOSPHERE SURFACE AND SUBSURFACE IN PLANETARY GEOCHEMISTRY AND CLIMATE STUDIES. UNTIL IN-SITU MEASUREMENTS CAN BE MADE REGULARLY THERMODYNAMIC MODELING IN WHICH AN EQUATION OF STATE (EOS) IS DEVELOPED TO REPRESENT THE CHEMICAL SYSTEMS IS THE BEST WAY FOR ANALYSES. CONVENTIONAL EOS E.G. VIRIAL AND CUBIC EOS CANNOT DEAL WITH CONDENSED PHASES AND ARE HANDICAPPED BY LIMITING ASSUMPTIONS THAT HINDER THEIR APPLICABILITY TO THE NON-IDEAL SYSTEMS ON PLANETARY BODIES. A RECENTLY DEVELOPED EOS REFERRED TO AS CRYOCHEM HAS BEEN SUCCESSFULLY APPLIED TO MODEL TITAN'S LOWER TROPOSPHERE (TAN ET AL. ICARUS 2013 222 53) AND THEN EXTENDED UP TO THE TROPOPAUSE AFTER INCLUDING SOLID PHASES (TAN&KARGEL FPE 2018 458 153) WHERE HUYGENS DATA OF METHANE MOLE FRACTION IS WELL REPRODUCED. THE MODEL ALSO MADE PREDICTIONS ON SURFACE-LIQUID COMPOSITIONS THAT ARE CONSISTENT WITH RELATED OBSERVATIONS I.E. TITAN'S NORTHERN LAKES WERE CORRECTLY PREDICTED TO BE RICH WITH METHANE INSTEAD OF ETHANE (TAN ET AL. ICARUS 2015 250 64) AS ALSO DERIVED FROM OBSERVATIONS BY CASSINI (MASTROGIUSEPPE ET AL. GEOPHYS. RES. LETT. 2013 41 1432). IN FURTHER APPLICATIONS WITH ITS ABILITY TO REPRESENT SOLID SOLUTIONS CRYOCHEM HAS SUCCESSFULLY DESCRIBED SOLID-PHASE EQUILIBRIA ON PLUTO'S SURFACE (TAN&KARGEL MNRAS 2018 474 4254) THAT ARE CONSISTENT WITH RECENT WORK DERIVED FROM OBSERVATIONS BY NEW HORIZONS. IT CONSISTENTLY DESCRIBED THE CONDITIONS AT WHICH THE SOLID PHASE IS METHANE-RICH OR NITROGEN-RICH. IN EFFORTS TO DESCRIBE PLANETARY SUBSURFACE THE BEHAVIOR OF CONDENSED PHASES MUST BE UNDER STRONG PRESSURE GRADIENT DUE TO THE GRAVITY AND IF WE GO DEEPER IS SUBJECT TO EVEN HIGHER PRESSURE DUE TO THE OVERLYING CRUST WHICH IS WATER ICE ON MANY COLD PLANETARY BODIES. ON TITAN THE CONDENSED PHASE OF INTEREST IS LIQUID AS THE LIQUID BODY IN THE LAKES OR AS THE ALKANOFER (VANCE ET AL. 43RD LPSC 2012 TEXAS # 2939 2012) ANALOGOUS TO AQUIFER ON EARTH AS PARTS OF THE ALKANOLOGY (ANALOGOUS TO EARTH'S HYDROLOGY) THAT MAY CONNECT SURFACE-LIQUID BODIES. IN THE LAKES WE HAVE SIMILAR SITUATION IN EVALUATING THE POSSIBILITY OF PHASE CHANGES THAT MAY LEAD TO BUBBLING OR FLOATING/SUSPENDED SOLID AS A VALID EXPLANATION OF "MAGIC ISLANDS" OBSERVED IN CASSINI'S FLYBYS. ON PLUTO THE CONDENSED PHASE IS SOLID VOLATILE ICES. IT IS OF OUR INTEREST TO KNOW IF THERE IS A POINT BENEATH THE SURFACE WHERE THE ICE MELTS THE OCCURRENCE OF WHICH MAY EXPLAIN THE HYPOTHETICAL FLUVIAL OR GLACIAL ACTIONS THAT RESULT IN VALLEY NETWORKS AND CHANNELS OBSERVED BY NEW HORIZONS. IN ADDITION TO THE PRESSURE GRADIENT THE SUBSURFACE SYSTEMS ARE ALSO SUBJECT TO TEMPERATURE GRADIENT OF THE CRUST. THEREFORE THIS PROPOSED WORK WILL ADDRESS THE BALANCING OF CHEMICAL-GRAVITATIONAL-THERMAL DIFFUSIVE POTENTIALS TO OBTAIN THE COMPOSITION GRADING WITH DEPTH FOR SUBSURFACE APPLICATIONS. THIS WAY THE HYDROSTATIC AND THERMAL DIFFUSION EFFECTS ARE EMBEDDED IN THE PHASE CALCULATIONS WHICH MAKE THE MODELING MORE REALISTIC. SIMILAR PHYSICS ALSO OCCURS IN THE PLANETARY ATMOSPHERES THE PROPERTIES OF WHICH HAVE BEEN MEASURED OR WELL DERIVED FROM OBSERVATIONS. THIS WORK WILL USE THE ATMOSPHERIC CASES FOR VALIDATION PURPOSES: UPON INPUTTING THE TEMPERATURE PROFILES THE CALCULATED PRESSURE PROFILES CAN BE MATCHED WITH THE OBSERVED DATA. IN SUMMARY THE MODIFICATIONS OF THE EOS WILL PROVIDE BETTER ACCURACY IN MODELING ANALYSIS AND INTERPRETATION OF PLANETARY DATA WHICH ARE DIRECTLY RELEVANT TO THE SSW PROGRAM GOAL TO IMPROVE UNDERSTANDING OF PHYSICAL AND CHEMICAL PROCESSES THAT AFFECT PLANETARY SURFACES CRUSTS OCEANS AND ATMOSPHERES.