diff --git a/include/cantera/thermo/VPSSMgr.h b/include/cantera/thermo/VPSSMgr.h
index da785f04b..7155a4d2b 100644
--- a/include/cantera/thermo/VPSSMgr.h
+++ b/include/cantera/thermo/VPSSMgr.h
@@ -677,8 +677,8 @@ protected:
     //! properties were calculated at.
     mutable doublereal m_plast;
 
-    //! Reference pressure (Pa) must be the same for all species - defaults to 1 atm.
-    mutable doublereal m_p0;
+    //! Reference pressure (Pa) for each species
+    mutable vector_fp m_p0;
 
     //! minimum temperature for the standard state calculations
     doublereal m_minTemp;
diff --git a/include/cantera/thermo/VPStandardStateTP.h b/include/cantera/thermo/VPStandardStateTP.h
index a6d0a4133..c70c1b4bc 100644
--- a/include/cantera/thermo/VPStandardStateTP.h
+++ b/include/cantera/thermo/VPStandardStateTP.h
@@ -287,12 +287,6 @@ protected:
     //! were calculated at.
     mutable doublereal m_Plast_ss;
 
-    /*!
-     * Reference pressure (Pa) must be the same for all species
-     * - defaults to OneAtm
-     */
-    doublereal m_P0;
-
     // -> suggest making this private!
     //! Pointer to the VPSS manager that calculates all of the standard state
     //! info efficiently.
diff --git a/src/thermo/VPSSMgr.cpp b/src/thermo/VPSSMgr.cpp
index 6a6f732aa..98e871f19 100644
--- a/src/thermo/VPSSMgr.cpp
+++ b/src/thermo/VPSSMgr.cpp
@@ -28,7 +28,6 @@ VPSSMgr::VPSSMgr(VPStandardStateTP* vptp_ptr, MultiSpeciesThermo* spthermo) :
     m_spthermo(spthermo),
     m_tlast(-1.0),
     m_plast(-1.0),
-    m_p0(-1.0),
     m_minTemp(-1.0),
     m_maxTemp(1.0E8),
     m_useTmpRefStateStorage(false),
@@ -266,10 +265,10 @@ void VPSSMgr::initLengths()
 
 void VPSSMgr::initThermoXML(XML_Node& phaseNode, const std::string& id)
 {
-    const PDSS* kPDSS = m_vptp_ptr->providePDSS(0);
-    m_p0 = kPDSS->refPressure();
     for (size_t i = 0; i < m_kk; i++) {
         const PDSS* kPDSS = m_vptp_ptr->providePDSS(i);
+        m_p0.resize(std::max(m_p0.size(), i+1));
+        m_p0[i] = kPDSS->refPressure();
         m_minTemp = std::max(m_minTemp, kPDSS->minTemp());
         m_maxTemp = std::min(m_maxTemp, kPDSS->maxTemp());
     }
@@ -281,9 +280,8 @@ void VPSSMgr::installSTSpecies(size_t k, const XML_Node& s,
     shared_ptr<SpeciesThermoInterpType> stit(newSpeciesThermoInterpType(s.child("thermo")));
     stit->validate(s["name"]);
     m_spthermo->install_STIT(k, stit);
-    if (m_p0 < 0.0) {
-        m_p0 = m_spthermo->refPressure(k);
-    }
+    m_p0.resize(std::max(m_p0.size(), k+1));
+    m_p0[k] = m_spthermo->refPressure(k);
 }
 
 PDSS* VPSSMgr::createInstallPDSS(size_t k, const XML_Node& s,
@@ -315,7 +313,7 @@ doublereal VPSSMgr::refPressure(size_t k) const
     if (k != npos) {
         return m_vptp_ptr->providePDSS(k)->refPressure();
     }
-    return m_p0;
+    return m_p0[0];
 }
 
 }
diff --git a/src/thermo/VPSSMgr_ConstVol.cpp b/src/thermo/VPSSMgr_ConstVol.cpp
index 69c9b136d..c6edd0895 100644
--- a/src/thermo/VPSSMgr_ConstVol.cpp
+++ b/src/thermo/VPSSMgr_ConstVol.cpp
@@ -34,10 +34,9 @@ VPSSMgr_ConstVol::VPSSMgr_ConstVol(VPStandardStateTP* vp_ptr, MultiSpeciesThermo
  */
 void VPSSMgr_ConstVol::_updateStandardStateThermo()
 {
-    doublereal del_pRT = (m_plast - m_p0) / (GasConstant * m_tlast);
-
     for (size_t k = 0; k < m_kk; k++) {
-        m_hss_RT[k] = m_h0_RT[k] + del_pRT * m_Vss[k];
+        m_hss_RT[k] = m_h0_RT[k]
+                    + (m_plast - m_p0[k]) / (GasConstant * m_tlast) * m_Vss[k];
         m_cpss_R[k] = m_cp0_R[k];
         m_sss_R[k] = m_s0_R[k];
         m_gss_RT[k] = m_hss_RT[k] - m_sss_R[k];
diff --git a/src/thermo/VPSSMgr_General.cpp b/src/thermo/VPSSMgr_General.cpp
index 6edf0e4bc..3605d5e52 100644
--- a/src/thermo/VPSSMgr_General.cpp
+++ b/src/thermo/VPSSMgr_General.cpp
@@ -146,10 +146,8 @@ PDSS* VPSSMgr_General::createInstallPDSS(size_t k, const XML_Node& speciesNode,
     m_kk = std::max(m_kk, k+1);
     m_minTemp = std::max(m_minTemp, kPDSS->minTemp());
     m_maxTemp = std::min(m_maxTemp, kPDSS->maxTemp());
-    doublereal p0 = kPDSS->refPressure();
-    if (k == 0) {
-        m_p0 = p0;
-    }
+    m_p0.resize(std::max(m_p0.size(), k+1));
+    m_p0[k] = kPDSS->refPressure();
     return kPDSS;
 }
 
diff --git a/src/thermo/VPSSMgr_IdealGas.cpp b/src/thermo/VPSSMgr_IdealGas.cpp
index 40d184256..7423f2d3c 100644
--- a/src/thermo/VPSSMgr_IdealGas.cpp
+++ b/src/thermo/VPSSMgr_IdealGas.cpp
@@ -43,13 +43,12 @@ void VPSSMgr_IdealGas::getStandardVolumes(doublereal* vol) const
 
 void VPSSMgr_IdealGas::_updateStandardStateThermo()
 {
-    doublereal pp = log(m_plast / m_p0);
     doublereal v = temperature() *GasConstant /m_plast;
 
     for (size_t k = 0; k < m_kk; k++) {
         m_hss_RT[k] = m_h0_RT[k];
         m_cpss_R[k] = m_cp0_R[k];
-        m_sss_R[k] = m_s0_R[k] - pp;
+        m_sss_R[k] = m_s0_R[k] - log(m_plast / m_p0[k]);
         m_gss_RT[k] = m_hss_RT[k] - m_sss_R[k];
         m_Vss[k] = v;
     }
@@ -76,7 +75,7 @@ PDSS* VPSSMgr_IdealGas::createInstallPDSS(size_t k, const XML_Node& speciesNode,
     PDSS* kPDSS = new PDSS_IdealGas(m_vptp_ptr, k, speciesNode,
                                     *phaseNode_ptr, true);
 
-    m_p0 = m_spthermo->refPressure(k);
+    m_p0[k] = m_spthermo->refPressure(k);
     return kPDSS;
 }
 
diff --git a/src/thermo/VPSSMgr_Water_ConstVol.cpp b/src/thermo/VPSSMgr_Water_ConstVol.cpp
index a68dcd725..ed934a33f 100644
--- a/src/thermo/VPSSMgr_Water_ConstVol.cpp
+++ b/src/thermo/VPSSMgr_Water_ConstVol.cpp
@@ -33,9 +33,9 @@ VPSSMgr_Water_ConstVol::VPSSMgr_Water_ConstVol(VPStandardStateTP* vp_ptr,
 void VPSSMgr_Water_ConstVol::getEnthalpy_RT_ref(doublereal* hrt) const
 {
     // Everything should be OK except for the water SS
-    m_p0 = m_waterSS->pref_safe(m_tlast);
-    if (m_p0 != m_plast) {
-        m_waterSS->setState_TP(m_tlast, m_p0);
+    m_p0[0] = m_waterSS->pref_safe(m_tlast);
+    if (m_p0[0] != m_plast) {
+        m_waterSS->setState_TP(m_tlast, m_p0[0]);
         m_h0_RT[0] = (m_waterSS->enthalpy_mole()) / (GasConstant * m_tlast);
         m_waterSS->setState_TP(m_tlast, m_plast);
     } else {
@@ -47,9 +47,9 @@ void VPSSMgr_Water_ConstVol::getEnthalpy_RT_ref(doublereal* hrt) const
 void VPSSMgr_Water_ConstVol::getGibbs_RT_ref(doublereal* grt) const
 {
     // Everything should be OK except for the water SS
-    m_p0 = m_waterSS->pref_safe(m_tlast);
-    if (m_p0 != m_plast) {
-        m_waterSS->setState_TP(m_tlast, m_p0);
+    m_p0[0] = m_waterSS->pref_safe(m_tlast);
+    if (m_p0[0] != m_plast) {
+        m_waterSS->setState_TP(m_tlast, m_p0[0]);
         m_g0_RT[0] = (m_waterSS->gibbs_mole()) / (GasConstant * m_tlast);
         m_waterSS->setState_TP(m_tlast, m_plast);
     } else {
@@ -69,9 +69,9 @@ void VPSSMgr_Water_ConstVol::getGibbs_ref(doublereal* g) const
 void VPSSMgr_Water_ConstVol::getEntropy_R_ref(doublereal* sr) const
 {
     // Everything should be OK except for the water SS
-    m_p0 = m_waterSS->pref_safe(m_tlast);
-    if (m_p0 != m_plast) {
-        m_waterSS->setState_TP(m_tlast, m_p0);
+    m_p0[0] = m_waterSS->pref_safe(m_tlast);
+    if (m_p0[0] != m_plast) {
+        m_waterSS->setState_TP(m_tlast, m_p0[0]);
         m_s0_R[0] = (m_waterSS->entropy_mole()) / GasConstant;
         m_waterSS->setState_TP(m_tlast, m_plast);
     } else {
@@ -83,9 +83,9 @@ void VPSSMgr_Water_ConstVol::getEntropy_R_ref(doublereal* sr) const
 void VPSSMgr_Water_ConstVol::getCp_R_ref(doublereal* cpr) const
 {
     // Everything should be OK except for the water SS
-    m_p0 = m_waterSS->pref_safe(m_tlast);
-    if (m_p0 != m_plast) {
-        m_waterSS->setState_TP(m_tlast, m_p0);
+    m_p0[0] = m_waterSS->pref_safe(m_tlast);
+    if (m_p0[0] != m_plast) {
+        m_waterSS->setState_TP(m_tlast, m_p0[0]);
         m_cp0_R[0] = (m_waterSS->cp_mole()) / GasConstant;
         m_waterSS->setState_TP(m_tlast, m_plast);
     } else {
@@ -97,9 +97,9 @@ void VPSSMgr_Water_ConstVol::getCp_R_ref(doublereal* cpr) const
 void VPSSMgr_Water_ConstVol::getStandardVolumes_ref(doublereal* vol) const
 {
     // Everything should be OK except for the water SS
-    m_p0 = m_waterSS->pref_safe(m_tlast);
-    if (m_p0 != m_plast) {
-        m_waterSS->setState_TP(m_tlast, m_p0);
+    m_p0[0] = m_waterSS->pref_safe(m_tlast);
+    if (m_p0[0] != m_plast) {
+        m_waterSS->setState_TP(m_tlast, m_p0[0]);
         m_V0[0] = m_vptp_ptr->molecularWeight(0) / m_waterSS->density();
         m_waterSS->setState_TP(m_tlast, m_plast);
     } else {
@@ -110,27 +110,25 @@ void VPSSMgr_Water_ConstVol::getStandardVolumes_ref(doublereal* vol) const
 
 void VPSSMgr_Water_ConstVol::_updateRefStateThermo() const
 {
-    m_p0 = m_waterSS->pref_safe(m_tlast);
+    m_p0[0] = m_waterSS->pref_safe(m_tlast);
     m_spthermo->update(m_tlast, &m_cp0_R[0], &m_h0_RT[0], &m_s0_R[0]);
     for (size_t k = 0; k < m_kk; k++) {
         m_g0_RT[k] = m_h0_RT[k] - m_s0_R[k];
         m_vptp_ptr->providePDSS(k)->setTemperature(m_tlast);
     }
-    m_waterSS->setState_TP(m_tlast, m_p0);
+    m_waterSS->setState_TP(m_tlast, m_p0[0]);
     m_h0_RT[0] = (m_waterSS->enthalpy_mole()) / (GasConstant * m_tlast);
     m_s0_R[0] = (m_waterSS->entropy_mole()) / GasConstant;
     m_cp0_R[0] = (m_waterSS->cp_mole()) / GasConstant;
-    m_g0_RT[0] = (m_hss_RT[0] - m_sss_R[0]);
-    m_V0[0] = m_vptp_ptr->molecularWeight(0) / (m_waterSS->density());
+    m_g0_RT[0] = (m_h0_RT[0] - m_s0_R[0]);
+    m_V0[0] = m_waterSS->molarVolume();
     m_waterSS->setState_TP(m_tlast, m_plast);
 }
 
 void VPSSMgr_Water_ConstVol::_updateStandardStateThermo()
 {
-    doublereal del_pRT = (m_plast - OneAtm) / (GasConstant * m_tlast);
-
     for (size_t k = 1; k < m_kk; k++) {
-        m_hss_RT[k] = m_h0_RT[k] + del_pRT * m_Vss[k];
+        m_hss_RT[k] = m_h0_RT[k] + (m_plast - m_p0[k]) / (GasConstant * m_tlast) * m_Vss[k];
         m_cpss_R[k] = m_cp0_R[k];
         m_sss_R[k] = m_s0_R[k];
         m_gss_RT[k] = m_hss_RT[k] - m_sss_R[k];
@@ -144,7 +142,7 @@ void VPSSMgr_Water_ConstVol::_updateStandardStateThermo()
     m_sss_R[0] = (m_waterSS->entropy_mole()) / GasConstant;
     m_cpss_R[0] = (m_waterSS->cp_mole()) / GasConstant;
     m_gss_RT[0] = (m_hss_RT[0] - m_sss_R[0]);
-    m_Vss[0] = (m_vptp_ptr->molecularWeight(0) / m_waterSS->density());
+    m_Vss[0] = m_waterSS->molarVolume();
 }
 
 void VPSSMgr_Water_ConstVol::initThermoXML(XML_Node& phaseNode,
@@ -225,6 +223,7 @@ PDSS* VPSSMgr_Water_ConstVol::createInstallPDSS(size_t k,
 
         // instantiate a new kPDSS object
         kPDSS = new PDSS_ConstVol(m_vptp_ptr, k, speciesNode, *phaseNode_ptr, true);
+        m_p0[k] = kPDSS->refPressure();
     }
     return kPDSS;
 }
diff --git a/src/thermo/VPSSMgr_Water_HKFT.cpp b/src/thermo/VPSSMgr_Water_HKFT.cpp
index c3a4fe066..a26dab75c 100644
--- a/src/thermo/VPSSMgr_Water_HKFT.cpp
+++ b/src/thermo/VPSSMgr_Water_HKFT.cpp
@@ -110,8 +110,8 @@ void VPSSMgr_Water_HKFT::updateRefStateThermo() const
 
 void VPSSMgr_Water_HKFT::_updateRefStateThermo() const
 {
-    m_p0 = m_waterSS->pref_safe(m_tlast);
-    m_waterSS->setState_TP(m_tlast, m_p0);
+    m_p0[0] = m_waterSS->pref_safe(m_tlast);
+    m_waterSS->setState_TP(m_tlast, m_p0[0]);
     m_h0_RT[0] = (m_waterSS->enthalpy_mole()) / (GasConstant * m_tlast);
     m_s0_R[0] = (m_waterSS->entropy_mole()) / GasConstant;
     m_cp0_R[0] = (m_waterSS->cp_mole()) / GasConstant;
@@ -120,7 +120,7 @@ void VPSSMgr_Water_HKFT::_updateRefStateThermo() const
     PDSS* ps;
     for (size_t k = 1; k < m_kk; k++) {
         ps = m_vptp_ptr->providePDSS(k);
-        ps->setState_TP(m_tlast, m_p0);
+        ps->setState_TP(m_tlast, m_p0[0]);
         m_cp0_R[k] = ps->cp_R();
         m_s0_R[k] = ps->entropy_mole() / GasConstant;
         m_g0_RT[k] = ps->gibbs_RT();
diff --git a/src/thermo/VPStandardStateTP.cpp b/src/thermo/VPStandardStateTP.cpp
index a25d58fca..6373e097a 100644
--- a/src/thermo/VPStandardStateTP.cpp
+++ b/src/thermo/VPStandardStateTP.cpp
@@ -20,8 +20,7 @@ namespace Cantera
 VPStandardStateTP::VPStandardStateTP() :
     m_Pcurrent(OneAtm),
     m_Tlast_ss(-1.0),
-    m_Plast_ss(-1.0),
-    m_P0(OneAtm)
+    m_Plast_ss(-1.0)
 {
 }
 
diff --git a/test/data/HMW_NaCl.xml b/test/data/HMW_NaCl.xml
new file mode 100644
index 000000000..3d9e100f6
--- /dev/null
+++ b/test/data/HMW_NaCl.xml
@@ -0,0 +1,252 @@
+<?xml version="1.0"?>
+<ctml>
+  <phase id="water_constvol" dim="3">
+    <speciesArray datasrc="#species_waterSolution">
+               H2O(L) Cl- H+ Na+ OH-
+    </speciesArray>
+    <state>
+      <temperature units="K"> 298.15 </temperature>
+      <pressure units="Pa"> 101325.0 </pressure>
+      <soluteMolalities>
+             Na+:6.0954
+             Cl-:6.0954
+             H+:2.1628E-9
+             OH-:1.3977E-6
+      </soluteMolalities>
+    </state>
+    <thermo model="HMW">
+       <variablePressureStandardStateManager model="water_constvol" />
+       <standardConc model="solvent_volume" />
+       <activityCoefficients model="Pitzer">
+                <A_Debye> 1.175930 </A_Debye>
+                <B_Debye> 3.28640E9 </B_Debye>
+                <ionicRadius default="3.042843"  units="Angstroms">
+                </ionicRadius>
+                <binarySaltParameters cation="Na+" anion="Cl-">
+                  <beta0> 0.0765 </beta0>
+                  <beta1> 0.2664 </beta1>
+                  <beta2> 0.0    </beta2>
+                  <Cphi> 0.00127 </Cphi>
+                  <Alpha1> 2.0 </Alpha1>
+                </binarySaltParameters>
+
+                <binarySaltParameters cation="H+" anion="Cl-">
+                  <beta0> 0.1775 </beta0>
+                  <beta1> 0.2945 </beta1>
+                  <beta2> 0.0    </beta2>
+                  <Cphi> 0.0008 </Cphi>
+                  <Alpha1> 2.0 </Alpha1>
+                </binarySaltParameters>
+
+                <binarySaltParameters cation="Na+" anion="OH-">
+                  <beta0> 0.0864 </beta0>
+                  <beta1> 0.253 </beta1>
+                  <beta2> 0.0    </beta2>
+                  <Cphi> 0.0044 </Cphi>
+                  <Alpha1> 2.0 </Alpha1>
+                </binarySaltParameters>
+
+                <thetaAnion anion1="Cl-" anion2="OH-">
+                  <theta> -0.05 </theta>
+                </thetaAnion>
+
+                <psiCommonCation cation="Na+" anion1="Cl-" anion2="OH-">
+                  <theta> -0.05 </theta>
+                  <Psi> -0.006 </Psi>
+                </psiCommonCation>
+
+                <thetaCation cation1="Na+" cation2="H+">
+                  <theta> 0.036 </theta>
+                </thetaCation>
+
+                <psiCommonAnion anion="Cl-" cation1="Na+" cation2="H+">
+                  <Theta> 0.036 </Theta>
+                  <Psi> -0.004 </Psi>
+                </psiCommonAnion>
+
+       </activityCoefficients>
+       <solvent> H2O(L) </solvent>
+    </thermo>
+    <elementArray datasrc="elements.xml"> O H C E Fe Si N Na Cl </elementArray>
+  </phase>
+
+  <phase id="general" dim="3">
+    <speciesArray datasrc="#species_waterSolution">
+               H2O(L) Cl- H+ Na+ OH-
+    </speciesArray>
+    <state>
+      <temperature units="K"> 298.15 </temperature>
+      <pressure units="Pa"> 101325.0 </pressure>
+      <soluteMolalities>
+             Na+:6.0954
+             Cl-:6.0954
+             H+:2.1628E-9
+             OH-:1.3977E-6
+      </soluteMolalities>
+    </state>
+    <!-- thermo model identifies the inherited class
+         from ThermoPhase that will handle the thermodynamics.
+      -->
+    <thermo model="HMW">
+       <variablePressureStandardStateManager model="general" />
+       <standardConc model="solvent_volume" />
+       <activityCoefficients model="Pitzer">
+                <!-- A_Debye units = sqrt(kg/gmol)
+                     This is adjusted to match the GWB value so
+                     that numerical comparisons can be made
+                     Aln = 0.5107
+                  -->
+                <A_Debye> 1.175930 </A_Debye>
+                <!-- B_Debye units = sqrt(kg/gmol)/m
+                  -->
+                <B_Debye> 3.28640E9 </B_Debye>
+                <ionicRadius default="3.042843"  units="Angstroms">
+                </ionicRadius>
+                <binarySaltParameters cation="Na+" anion="Cl-">
+                  <beta0> 0.0765 </beta0>
+                  <beta1> 0.2664 </beta1>
+                  <beta2> 0.0    </beta2>
+                  <Cphi> 0.00127 </Cphi>
+                  <Alpha1> 2.0 </Alpha1>
+                </binarySaltParameters>
+
+                <binarySaltParameters cation="H+" anion="Cl-">
+                  <beta0> 0.1775 </beta0>
+                  <beta1> 0.2945 </beta1>
+                  <beta2> 0.0    </beta2>
+                  <Cphi> 0.0008 </Cphi>
+                  <Alpha1> 2.0 </Alpha1>
+                </binarySaltParameters>
+
+                <binarySaltParameters cation="Na+" anion="OH-">
+                  <beta0> 0.0864 </beta0>
+                  <beta1> 0.253 </beta1>
+                  <beta2> 0.0    </beta2>
+                  <Cphi> 0.0044 </Cphi>
+                  <Alpha1> 2.0 </Alpha1>
+                </binarySaltParameters>
+
+                <thetaAnion anion1="Cl-" anion2="OH-">
+                  <theta> -0.05 </theta>
+                </thetaAnion>
+
+                <psiCommonCation cation="Na+" anion1="Cl-" anion2="OH-">
+                  <theta> -0.05 </theta>
+                  <Psi> -0.006 </Psi>
+                </psiCommonCation>
+
+                <thetaCation cation1="Na+" cation2="H+">
+                  <theta> 0.036 </theta>
+                </thetaCation>
+
+                <psiCommonAnion anion="Cl-" cation1="Na+" cation2="H+">
+                  <Theta> 0.036 </Theta>
+                  <Psi> -0.004 </Psi>
+                </psiCommonAnion>
+
+       </activityCoefficients>
+       <solvent> H2O(L) </solvent>
+    </thermo>
+    <elementArray datasrc="elements.xml"> O H C E Fe Si N Na Cl </elementArray>
+  </phase>
+
+
+  <speciesData id="species_waterSolution">
+
+    <species name="H2O(L)">
+      <atomArray>H:2 O:1 </atomArray>
+      <thermo>
+        <NASA Tmax="600.0" Tmin="273.14999999999998" P0="100000.0">
+           <floatArray name="coeffs" size="7">
+             7.255750050E+01,  -6.624454020E-01,   2.561987460E-03,  -4.365919230E-06,
+             2.781789810E-09,  -4.188654990E+04,  -2.882801370E+02
+           </floatArray>
+        </NASA>
+      </thermo>
+      <standardState model="waterIAPWS">
+      </standardState>
+    </species>
+
+    <species name="Na+">
+      <atomArray> Na:1 E:-1 </atomArray>
+      <charge> +1 </charge>
+      <thermo>
+       <Mu0 Pref="100000.0" Tmax="1000.0" Tmin="200.0">
+         <H298 units="cal/mol"> 0.0  </H298>
+         <numPoints> 2            </numPoints>
+         <floatArray size="2" title="Mu0Values" units="Dimensionless">
+             -125.5213,  -125.5213
+         </floatArray>
+          <floatArray size="2" title="Mu0Temperatures">
+             298.15,    333.15
+          </floatArray>
+       </Mu0>
+      </thermo>
+      <standardState model="constant_incompressible">
+         <molarVolume> 1.3 </molarVolume>
+      </standardState>
+    </species>
+
+    <species name="Cl-">
+      <atomArray> Cl:1 E:1 </atomArray>
+      <charge> -1 </charge>
+      <standardState model="constant_incompressible">
+          <molarVolume> 1.3 </molarVolume>
+      </standardState>
+      <thermo>
+        <Mu0 Pref="100000.0" Tmax="333." Tmin="298.">
+         <H298 units="cal/mol"> 0.0  </H298>
+         <numPoints> 2            </numPoints>
+         <floatArray size="2" title="Mu0Values" units="Dimensionless">
+            -52.8716 , -52.8716
+         </floatArray>
+          <floatArray size="2" title="Mu0Temperatures">
+             298.15,    333.15
+          </floatArray>
+        </Mu0>
+      </thermo>
+     </species>
+
+    <species name="H+">
+      <atomArray> H:1 E:-1 </atomArray>
+      <charge> +1 </charge>
+      <standardState model="constant_incompressible">
+          <molarVolume> 1.3 </molarVolume>
+      </standardState>
+      <thermo>
+        <Mu0 Pref="100000.0" Tmax="333." Tmin="298.">
+         <H298 units="cal/mol"> 0.0  </H298>
+         <numPoints> 2            </numPoints>
+         <floatArray size="2" title="Mu0Values" units="Dimensionless">
+            0.0 , 0.0
+         </floatArray>
+          <floatArray size="2" title="Mu0Temperatures">
+             298.15,    333.15
+          </floatArray>
+        </Mu0>
+      </thermo>
+     </species>
+
+    <species name="OH-">
+      <atomArray> O:1 H:1 E:1 </atomArray>
+      <charge> -1 </charge>
+      <standardState model="constant_incompressible">
+          <molarVolume> 1.3 </molarVolume>
+      </standardState>
+      <thermo>
+        <Mu0 Pref="100000.0" Tmax="333." Tmin="298.">
+         <H298 units="cal/mol"> 0.0  </H298>
+         <numPoints> 2            </numPoints>
+         <floatArray size="2" title="Mu0Values" units="Dimensionless">
+            -91.523 ,  -91.523
+         </floatArray>
+          <floatArray size="2" title="Mu0Temperatures">
+             298.15,    333.15
+          </floatArray>
+        </Mu0>
+      </thermo>
+     </species>
+
+  </speciesData>
+
+</ctml>
diff --git a/test/thermo/standardStateManagers.cpp b/test/thermo/standardStateManagers.cpp
new file mode 100644
index 000000000..754539f8c
--- /dev/null
+++ b/test/thermo/standardStateManagers.cpp
@@ -0,0 +1,59 @@
+#include "gtest/gtest.h"
+#include "cantera/thermo/HMWSoln.h"
+
+using namespace Cantera;
+
+TEST(HMW, VPSSMgrGeneral_vs_VPSSMgrWater_ConstVol)
+{
+    // Calculations should give the same result using either the generic
+    // VPSSMgr_General class or one of the more specialized classes such as
+    // VPSSMgr_Water_ConstVol.
+    HMWSoln p1("../data/HMW_NaCl.xml", "water_constvol");
+    HMWSoln p2("../data/HMW_NaCl.xml", "general");
+    size_t n = p1.nSpecies();
+    vector_fp molalities(n);
+    p1.getMolalities(molalities.data());
+    molalities[2] = 2.1628E-9;
+    molalities[3] = 6.0997;
+    molalities[4] = 1.3977E-6;
+    molalities[1] = molalities[2] + molalities[3] - molalities[4];
+    p1.setMolalities(molalities.data());
+    p2.setMolalities(molalities.data());
+    p1.setState_TP(310.15, 201325);
+    p2.setState_TP(310.15, 201325);
+
+    vector_fp v1(n);
+    vector_fp v2(n);
+    p1.getStandardVolumes(v1.data());
+    p2.getStandardVolumes(v2.data());
+    for (size_t i = 0; i < n; i++) {
+        EXPECT_NEAR(v1[i], v2[i], 1e-9) << p1.speciesName(i);
+    }
+
+    p1.getCp_R(v1.data());
+    p2.getCp_R(v2.data());
+    for (size_t i = 0; i < n; i++) {
+        EXPECT_NEAR(v1[i], v2[i], 1e-10) << p1.speciesName(i);
+    }
+
+    p1.getEntropy_R(v1.data());
+    p2.getEntropy_R(v2.data());
+    for (size_t i = 0; i < n; i++) {
+        EXPECT_NEAR(v1[i], v2[i], 1e-10) << p1.speciesName(i);
+    }
+
+    p1.getEnthalpy_RT(v1.data());
+    p2.getEnthalpy_RT(v2.data());
+    for (size_t i = 0; i < n; i++) {
+        EXPECT_NEAR(v1[i], v2[i], 1e-10) << p1.speciesName(i);
+    }
+
+    p1.getChemPotentials_RT(v1.data());
+    p2.getChemPotentials_RT(v2.data());
+    for (size_t i = 0; i < n; i++) {
+        EXPECT_NEAR(v1[i], v2[i], 1e-10) << p1.speciesName(i);
+    }
+
+    EXPECT_NEAR(p1.entropy_mole(), p2.entropy_mole(), 1e-7);
+    EXPECT_NEAR(p1.enthalpy_mole(), p2.enthalpy_mole(), 1e-4);
+}
diff --git a/test_problems/cathermo/HMW_test_1/output_noD_blessed.txt b/test_problems/cathermo/HMW_test_1/output_noD_blessed.txt
index 0d2dff721..879760ab0 100644
--- a/test_problems/cathermo/HMW_test_1/output_noD_blessed.txt
+++ b/test_problems/cathermo/HMW_test_1/output_noD_blessed.txt
@@ -37,22 +37,22 @@ a2 = 3.04284e-10
            Species   Standard chemical potentials (kJ/gmol) 
 ------------------------------------------------------------
           H2O(L)      -306.685728
-             Cl-      -131.066416
-              H+                0
-             Na+       -311.16189
-             OH-       -226.88157
+             Cl-      -131.064694
+              H+        0.0017225
+             Na+      -311.160167
+             OH-      -226.879848
 ------------------------------------------------------------
  Some DeltaSS values:               Delta(mu_0)
- NaCl(S): Na+ + Cl- -> NaCl(S):       9.597906 kJ/gmol 
-                                :       3.871747 (dimensionless) 
-                                :       1.681478 (dimensionless/ln10) 
+ NaCl(S): Na+ + Cl- -> NaCl(S):       9.594461 kJ/gmol 
+                                :       3.870358 (dimensionless) 
+                                :       1.680875 (dimensionless/ln10) 
             G0(NaCl(S)) =      -432.6304 (fixed)
-            G0(Na+)     =      -311.1619
-            G0(Cl-)     =      -131.0664
- OH-: H2O(L) - H+ -> OH-:       79.80416 kJ/gmol 
-                                :        32.1926 (dimensionless) 
-                                :       13.98107 (dimensionless/ln10) 
-            G0(OH-)    =      -226.8816
-            G0(H+)     =              0
+            G0(Na+)     =      -311.1602
+            G0(Cl-)     =      -131.0647
+ OH-: H2O(L) - H+ -> OH-:        79.8076 kJ/gmol 
+                                :       32.19399 (dimensionless) 
+                                :       13.98167 (dimensionless/ln10) 
+            G0(OH-)    =      -226.8798
+            G0(H+)     =      0.0017225
             G0(H2O(L)) =      -306.6857
 ------------------------------------------------------------
diff --git a/test_problems/cathermo/HMW_test_3/output_noD_blessed.txt b/test_problems/cathermo/HMW_test_3/output_noD_blessed.txt
index 4e19d7b6a..1c8217aa3 100644
--- a/test_problems/cathermo/HMW_test_3/output_noD_blessed.txt
+++ b/test_problems/cathermo/HMW_test_3/output_noD_blessed.txt
@@ -38,16 +38,16 @@ Index  Name                  MoleF   MolalityCropped  Charge
            Species   Standard chemical potentials (kJ/gmol) 
 ------------------------------------------------------------
           H2O(L)      -317.175788
-             Cl-      -186.016281
-              H+                0
-             Na+      -441.617151
-             OH-      -322.002134
+             Cl-      -186.014558
+              H+        0.0017225
+             Na+      -441.615429
+             OH-      -322.000412
 ------------------------------------------------------------
  Some DeltaSS values:               Delta(mu_0)
  NaCl(S): Na+ + Cl- -> NaCl(S):            195 kJ/gmol 
-                                :         78.663 (dimensionless) 
-                                :         34.163 (dimensionless/ln10) 
- OH-: H2O(L) - H+ -> OH-:        -4.8263 kJ/gmol 
-                                :        -1.9469 (dimensionless) 
-                                :       -0.84554 (dimensionless/ln10) 
+                                :         78.662 (dimensionless) 
+                                :         34.162 (dimensionless/ln10) 
+ OH-: H2O(L) - H+ -> OH-:        -4.8229 kJ/gmol 
+                                :        -1.9455 (dimensionless) 
+                                :       -0.84493 (dimensionless/ln10) 
 ------------------------------------------------------------