diff --git a/Cantera/src/thermo/IdealGasPDSS.cpp b/Cantera/src/thermo/IdealGasPDSS.cpp
new file mode 100644
index 000000000..3b49f49bb
--- /dev/null
+++ b/Cantera/src/thermo/IdealGasPDSS.cpp
@@ -0,0 +1,373 @@
+/**
+ * @file IdealGasPDSS.cpp
+ *
+ * Implementation of a pressure dependent standard state 
+ * virtual function.
+ */
+/*
+ * Copywrite (2006) Sandia Corporation. Under the terms of
+ * Contract DE-AC04-94AL85000 with Sandia Corporation, the
+ * U.S. Government retains certain rights in this software.
+ */
+/*
+ * $Id$
+ */
+
+#include "ct_defs.h"
+#include "xml.h"
+#include "ctml.h"
+#include "IdealGasPDSS.h"
+#include "importCTML.h"
+
+
+#include "ThermoPhase.h"
+
+using namespace std;
+
+namespace Cantera {
+  /**
+   * Basic list of constructors and duplicators
+   */
+
+  IdealGasPDSS::IdealGasPDSS(ThermoPhase *tp, int spindex) :
+    PDSS(tp, spindex)
+  {
+    constructPDSS(tp, spindex);
+  }
+
+
+  IdealGasPDSS::IdealGasPDSS(ThermoPhase *tp, int spindex, std::string inputFile, std::string id) :
+    PDSS(tp, spindex)
+  {
+    constructPDSSFile(tp, spindex, inputFile, id);
+  }
+
+
+  IdealGasPDSS::IdealGasPDSS(ThermoPhase *tp, int spindex, XML_Node& phaseRoot, std::string id) :
+    PDSS(tp, spindex)
+  {
+    constructPDSSXML(tp, spindex, phaseRoot, id) ;
+  }
+
+
+  IdealGasPDSS::IdealGasPDSS(const IdealGasPDSS &b) :
+    PDSS(b)
+  {
+    /*
+     * Use the assignment operator to do the brunt
+     * of the work for the copy construtor.
+     */
+    *this = b;
+  }
+
+  /**
+   * Assignment operator
+   */
+  IdealGasPDSS& IdealGasPDSS::operator=(const IdealGasPDSS&b) {
+    if (&b == this) return *this;
+    PDSS::operator=(b);
+    return *this;
+  }
+
+  IdealGasPDSS::~IdealGasPDSS() { 
+  }
+  
+  void IdealGasPDSS::constructPDSS(ThermoPhase *tp, int spindex) {
+    initThermo();
+  }
+
+   
+  /**
+   * constructPDSSXML:
+   *
+   * Initialization of a IdealGasPDSS object using an
+   * xml file.
+   *
+   * This routine is a precursor to initThermo(XML_Node*)
+   * routine, which does most of the work.
+   *
+   * @param infile XML file containing the description of the
+   *        phase
+   *
+   * @param id  Optional parameter identifying the name of the
+   *            phase. If none is given, the first XML
+   *            phase element will be used.
+   */
+  void IdealGasPDSS::constructPDSSXML(ThermoPhase *tp, int spindex, 
+			      XML_Node& phaseNode, std::string id) {
+    initThermo();
+  }
+
+   
+  /**
+   * constructPDSSFile():
+   *
+   * Initialization of a IdealGasPDSS object using an
+   * xml file.
+   *
+   * This routine is a precursor to initThermo(XML_Node*)
+   * routine, which does most of the work.
+   *
+   * @param infile XML file containing the description of the
+   *        phase
+   *
+   * @param id  Optional parameter identifying the name of the
+   *            phase. If none is given, the first XML
+   *            phase element will be used.
+   */
+  void IdealGasPDSS::constructPDSSFile(ThermoPhase *tp, int spindex,
+			       std::string inputFile, std::string id) {
+
+    if (inputFile.size() == 0) {
+      throw CanteraError("IdealGasPDSS::initThermo",
+			 "input file is null");
+    }
+    std::string path = findInputFile(inputFile);
+    ifstream fin(path.c_str());
+    if (!fin) {
+      throw CanteraError("IdealGasPDSS::initThermo","could not open "
+			 +path+" for reading.");
+    }
+    /*
+     * The phase object automatically constructs an XML object.
+     * Use this object to store information.
+     */
+
+    XML_Node *fxml = new XML_Node();
+    fxml->build(fin);
+    XML_Node *fxml_phase = findXMLPhase(fxml, id);
+    if (!fxml_phase) {
+      throw CanteraError("IdealGasPDSS::initThermo",
+			 "ERROR: Can not find phase named " +
+			 id + " in file named " + inputFile);
+    }	
+    constructPDSSXML(tp, spindex, *fxml_phase, id);
+    delete fxml;
+  }
+
+  void IdealGasPDSS::
+  initThermoXML(XML_Node& phaseNode, std::string id) {
+    initThermo();
+  }
+
+  void IdealGasPDSS::initThermo() {
+  }
+
+  void IdealGasPDSS::
+  setParametersFromXML(const XML_Node& eosdata) {
+  }
+
+  /**
+   * Return the molar enthalpy in units of J kmol-1
+   */
+  doublereal IdealGasPDSS::
+  enthalpy_mole() const {
+    throw CanteraError("IdealGasPDSS::enthalpy_mole()", "unimplemented");
+    return (0.0);
+  }
+
+  /**
+   * Calculate the internal energy in mks units of
+   * J kmol-1 
+   */
+  doublereal IdealGasPDSS::
+  intEnergy_mole() const {
+    throw CanteraError("IdealGasPDSS::enthalpy_mole()", "unimplemented");
+    return (0.0);
+  }
+
+  /**
+   * Calculate the entropy in mks units of 
+   * J kmol-1 K-1
+   */
+  doublereal IdealGasPDSS::
+  entropy_mole() const {
+
+    throw CanteraError("IdealGasPDSS::entropy_mole()", "unimplemented");
+    return (0.0);
+  }
+
+  /**
+   * Calculate the Gibbs free energy in mks units of
+   * J kmol-1 K-1.
+   */
+  doublereal IdealGasPDSS::
+  gibbs_mole() const {
+    throw CanteraError("IdealGasPDSS::gibbs_mole()", "unimplemented");
+    return (0.0);
+  }
+
+  /**
+   * Calculate the constant pressure heat capacity
+   * in mks units of J kmol-1 K-1
+   */
+  doublereal IdealGasPDSS::
+  cp_mole() const {
+    throw CanteraError("IdealGasPDSS::cp_mole()", "unimplemented");
+    return (0.0);
+  }
+
+  /**
+   * Calculate the constant volume heat capacity
+   * in mks units of J kmol-1 K-1
+   */
+  doublereal IdealGasPDSS::
+  cv_mole() const {
+    throw CanteraError("IdealGasPDSS::cv_mole()", "unimplemented");
+    return (0.0);
+  }
+
+   
+  /**
+   * Return the difference in enthalpy between current p
+   * and ref p0, in mks units of
+   * in units of J kmol-1
+   */
+  doublereal IdealGasPDSS::
+  enthalpyDelp_mole() const {
+    throw CanteraError("IdealGasPDSS::enthalpy_mole()", "unimplemented");
+    return (0.0);
+  }
+
+  /**
+   * Calculate difference in the internal energy between current p
+   * and ref p0, in mks units of
+   * J kmol-1 
+   */
+  doublereal IdealGasPDSS::
+  intEnergyDelp_mole() const {
+    throw CanteraError("IdealGasPDSS::enthalpyDelp_mole()", "unimplemented");
+    return (0.0);
+  }
+
+  /**
+   *  Return the difference in entropy between current p
+   * and ref p0, in mks units of
+   * J kmol-1 K-1
+   */
+  doublereal IdealGasPDSS::
+  entropyDelp_mole() const {
+
+    throw CanteraError("IdealGasPDSS::entropyDelp_mole()", "unimplemented");
+    return (0.0);
+  }
+
+  /**
+   * Calculate the difference in Gibbs free energy between current p and
+   * the ref p0, in mks units of
+   * J kmol-1 K-1.
+   */
+  doublereal IdealGasPDSS::
+  gibbsDelp_mole() const {
+    throw CanteraError("IdealGasPDSS::gibbsDelp_mole()", "unimplemented");
+    return (0.0);
+  }
+
+  /**
+   * Calculate the difference in the constant pressure heat capacity
+   * between the current p and the ref p0,
+   * in mks units of J kmol-1 K-1
+   */
+  doublereal IdealGasPDSS::
+  cpDelp_mole() const {
+    throw CanteraError("IdealGasPDSS::cpDelp_mole()", "unimplemented");
+    return (0.0);
+  }
+
+  /**
+   * Calculate the difference in constant volume heat capacity
+   * between the current p and the ref p0
+   * in mks units of J kmol-1 K-1
+   */
+  doublereal IdealGasPDSS::
+  cvDelp_mole() const {
+    throw CanteraError("IdealGasPDSS::cvDelp_mole()", "unimplemented");
+    return (0.0);
+  }
+
+  /**
+   * Calculate the pressure (Pascals), given the temperature and density
+   *  Temperature: kelvin
+   *  rho: density in kg m-3
+   */
+  doublereal IdealGasPDSS::
+  pressure() const {
+    throw CanteraError("IdealGasPDSS::pressure()", "unimplemented");
+    return (0.0);
+  }
+        
+  void IdealGasPDSS::
+  setPressure(doublereal p) {
+    throw CanteraError("IdealGasPDSS::pressure()", "unimplemented");
+  }
+ 
+
+  /// critical temperature 
+  doublereal IdealGasPDSS::critTemperature() const { 
+    throw CanteraError("IdealGasPDSS::critTemperature()", "unimplemented");
+    return (0.0);
+  }
+        
+  /// critical pressure
+  doublereal IdealGasPDSS::critPressure() const {
+    throw CanteraError("IdealGasPDSS::critPressure()", "unimplemented");
+    return (0.0);
+  }
+        
+  /// critical density
+  doublereal IdealGasPDSS::critDensity() const {
+    throw CanteraError("IdealGasPDSS::critDensity()", "unimplemented");
+    return (0.0);
+  }
+        
+  void IdealGasPDSS::setDensity(double dens) {
+    m_dens = dens;
+  }
+
+  /**
+   * Return the density of the standard state
+   *
+   *  We assume that the storred density is current.
+   * Note, this is the density of the standard state,
+   * not of the mixture.
+   */
+  double IdealGasPDSS::density() const {
+    return m_dens;
+  }
+
+  /**
+   * Return the temperature 
+   *
+   * Obtain the temperature from the owning ThermoPhase object
+   * if you can. 
+   */
+  double IdealGasPDSS::temperature() const {
+    if (m_tp) {
+      m_temp = m_tp->temperature();
+    }
+    return m_temp;
+  }
+ 
+  void IdealGasPDSS::setTemperature(double temp) {
+    m_temp = temp;
+  }
+
+  doublereal IdealGasPDSS::molecularWeight() const {
+    return m_mw;
+  }
+  void IdealGasPDSS::setMolecularWeight(double mw) {
+    m_mw = mw;
+  }
+
+  void IdealGasPDSS::setState_TP(double temp, double pres) {
+    throw CanteraError("IdealGasPDSS::setState_TP()", "unimplemented");
+  }
+
+  /// saturation pressure
+  doublereal IdealGasPDSS::satPressure(doublereal t){
+    throw CanteraError("IdealGasPDSS::satPressure()", "unimplemented");
+    return (0.0);
+  }
+    
+
+}
diff --git a/Cantera/src/thermo/IdealGasPDSS.h b/Cantera/src/thermo/IdealGasPDSS.h
new file mode 100644
index 000000000..beaa7fc73
--- /dev/null
+++ b/Cantera/src/thermo/IdealGasPDSS.h
@@ -0,0 +1,146 @@
+/**
+ *  @file IDEALGASPDSS.h
+ *
+ * Declares class PDSS pressure dependent standard state
+ * for a single species
+ */
+/*
+ * Copywrite (2006) Sandia Corporation. Under the terms of
+ * Contract DE-AC04-94AL85000 with Sandia Corporation, the
+ * U.S. Government retains certain rights in this software.
+ */
+/*
+ *  $Id$
+ */
+
+#ifndef CT_IDEALGASPDSS_H
+#define CT_IDEALGASPDSS_H
+
+#include "PDSS.h"
+
+class XML_Node;
+class ThermoPhase;
+
+namespace Cantera {
+
+
+  /**
+   * Class for pressure dependent standard states.
+   * This class is for a single Ideal Gas species.
+   *
+   */
+  class IdealGasPDSS : public PDSS {
+
+  public:
+
+    /**
+     * Basic list of constructors and duplicators
+     */
+    IdealGasPDSS(ThermoPhase *tp, int spindex);
+    IdealGasPDSS(const IdealGasPDSS &b);
+    IdealGasPDSS& operator=(const IdealGasPDSS&b);
+    IdealGasPDSS(ThermoPhase *tp, int spindex, std::string inputFile, std::string id = "");
+    IdealGasPDSS(ThermoPhase *tp, int spindex, XML_Node& phaseRef, std::string id = "");
+    virtual ~IdealGasPDSS();
+        
+    /**
+     *   
+     * @name  Utilities  
+     * @{
+     */
+    virtual int pdssType() const { return -1; }
+
+    /**
+     * @} 
+     * @name  Molar Thermodynamic Properties of the Solution --------------
+     * @{
+     */
+    virtual doublereal enthalpy_mole() const;
+    virtual doublereal intEnergy_mole() const;
+    virtual doublereal entropy_mole() const;
+    virtual doublereal gibbs_mole() const;
+    virtual doublereal cp_mole() const;
+    virtual doublereal cv_mole() const;
+
+    /*
+     * Get the difference in the standard state thermodynamic properties
+     * between the reference pressure, po, and the current pressure.
+     */
+    virtual doublereal enthalpyDelp_mole() const;
+    virtual doublereal intEnergyDelp_mole() const;
+    virtual doublereal entropyDelp_mole() const;
+    virtual doublereal gibbsDelp_mole() const;
+    virtual doublereal cpDelp_mole() const;
+    virtual doublereal cvDelp_mole() const;
+
+    //@}
+    /// @name Mechanical Equation of State Properties ---------------------
+    //@{
+
+    virtual doublereal pressure() const;
+    virtual void setPressure(doublereal p);
+
+    //@}
+    /// @name  Partial Molar Properties of the Solution -----------------
+    //@{
+
+    virtual void getChemPotentials(doublereal* mu) const {
+      mu[0] = gibbs_mole();
+    }
+
+    //@}
+    /// @name  Properties of the Standard State of the Species
+    //          in the Solution --
+    //@{
+    
+
+    /// critical temperature 
+    virtual doublereal critTemperature() const;
+ 
+    /// critical pressure
+    virtual doublereal critPressure() const;
+        
+    /// critical density
+    virtual doublereal critDensity() const;
+        
+    /// saturation temperature
+    //virtual doublereal satTemperature(doublereal p) const;
+        
+    
+
+    /// saturation pressure
+    virtual doublereal satPressure(doublereal t);
+    
+    virtual void setDensity(double dens);
+    double density() const;
+    virtual void setTemperature(double temp);
+    double temperature() const;
+    virtual void setState_TP(double temp, double pres);
+
+    doublereal molecularWeight() const;
+    void setMolecularWeight(double mw);
+    
+    virtual void constructPDSS(ThermoPhase *tp, int spindex);
+    virtual void constructPDSSFile(ThermoPhase *tp, int spindex, 
+				   std::string inputFile, std::string id);
+    virtual void constructPDSSXML(ThermoPhase *tp, int spindex, 
+				  XML_Node& phaseNode, std::string id);
+    virtual void initThermoXML(XML_Node& eosdata, std::string id);
+    virtual void initThermo();
+    virtual void setParametersFromXML(const XML_Node& eosdata);
+
+  protected:
+
+    int m_kk, m_mm;
+    doublereal m_tmin, m_tmax, m_p0;
+    
+  
+
+  };
+
+}
+
+#endif
+
+
+