diff --git a/include/cantera/equil/MultiPhase.h b/include/cantera/equil/MultiPhase.h
index 91304a7ac..7569202fb 100644
--- a/include/cantera/equil/MultiPhase.h
+++ b/include/cantera/equil/MultiPhase.h
@@ -452,7 +452,7 @@ public:
      *              Mole numbers that are less than or equal to zero will be
      *              set to zero. units = kmol.
      */
-    void setMolesByName(compositionMap& xMap);
+    void setMolesByName(const compositionMap& xMap);
 
     //! Set the moles via a string containing their names.
     /*!
diff --git a/include/cantera/thermo/MolalityVPSSTP.h b/include/cantera/thermo/MolalityVPSSTP.h
index 1406b994c..174d9db72 100644
--- a/include/cantera/thermo/MolalityVPSSTP.h
+++ b/include/cantera/thermo/MolalityVPSSTP.h
@@ -352,7 +352,7 @@ public:
      *
      * @param xMap  Composition Map containing the molalities.
      */
-    void setMolalitiesByName(compositionMap& xMap);
+    void setMolalitiesByName(const compositionMap& xMap);
 
     //! Set the molalities of a phase
     /*!
@@ -660,7 +660,7 @@ public:
      * @param p           Pressure (Pa)
      * @param m           compositionMap containing the molalities
      */
-    void setState_TPM(doublereal t, doublereal p, compositionMap& m);
+    void setState_TPM(doublereal t, doublereal p, const compositionMap& m);
 
     //! Set the temperature (K), pressure (Pa), and molalities.
     /*!
diff --git a/include/cantera/thermo/Phase.h b/include/cantera/thermo/Phase.h
index 736bb164b..9012a00cc 100644
--- a/include/cantera/thermo/Phase.h
+++ b/include/cantera/thermo/Phase.h
@@ -298,7 +298,7 @@ public:
     //! Set the species mole fractions by name.
     //! Species not listed by name in \c xMap are set to zero.
     //!     @param xMap map from species names to mole fraction values.
-    void setMoleFractionsByName(compositionMap& xMap);
+    void setMoleFractionsByName(const compositionMap& xMap);
 
     //! Set the mole fractions of a group of species by name. Species which
     //! are not listed by name in the composition map are set to zero.
@@ -308,7 +308,7 @@ public:
     //! Set the species mass fractions by name.
     //! Species not listed by name in \c yMap are set to zero.
     //!     @param yMap map from species names to mass fraction values.
-    void setMassFractionsByName(compositionMap& yMap);
+    void setMassFractionsByName(const compositionMap& yMap);
 
     //! Set the species mass fractions by name.
     //! Species not listed by name in \c x are set to zero.
@@ -327,7 +327,7 @@ public:
     //!     @param x     Composition Map containing the mole fractions.
     //!                  Species not included in the map are assumed to have
     //!                  a zero mole fraction.
-    void setState_TRX(doublereal t, doublereal dens, compositionMap& x);
+    void setState_TRX(doublereal t, doublereal dens, const compositionMap& x);
 
     //! Set the internally stored temperature (K), density, and mass fractions.
     //!     @param t     Temperature in kelvin
@@ -341,7 +341,7 @@ public:
     //!     @param y     Composition Map containing the mass fractions.
     //!                  Species not included in the map are assumed to have
     //!                  a zero mass fraction.
-    void setState_TRY(doublereal t, doublereal dens, compositionMap& y);
+    void setState_TRY(doublereal t, doublereal dens, const compositionMap& y);
 
     //! Set the internally stored temperature (K), molar density (kmol/m^3), and mole fractions.
     //!     @param t     Temperature in kelvin
diff --git a/include/cantera/thermo/SingleSpeciesTP.h b/include/cantera/thermo/SingleSpeciesTP.h
index d497ca4c6..d36d0ff86 100644
--- a/include/cantera/thermo/SingleSpeciesTP.h
+++ b/include/cantera/thermo/SingleSpeciesTP.h
@@ -423,7 +423,7 @@ public:
      * @param x    String containing a composition map of the mole fractions. Species not in
      *             the composition map are assumed to have zero mole fraction
      */
-    void setState_TPX(doublereal t, doublereal p, compositionMap& x);
+    void setState_TPX(doublereal t, doublereal p, const compositionMap& x);
 
     //! Set the temperature (K), pressure (Pa), and mole fractions.
     /*!
@@ -459,7 +459,7 @@ public:
      * @param y    Composition map of mass fractions. Species not in
      *             the composition map are assumed to have zero mass fraction
      */
-    void setState_TPY(doublereal t, doublereal p, compositionMap& y);
+    void setState_TPY(doublereal t, doublereal p, const compositionMap& y);
 
     //! Set the internally stored temperature (K), pressure (Pa), and mass fractions of the phase
     /*!
diff --git a/include/cantera/thermo/ThermoPhase.h b/include/cantera/thermo/ThermoPhase.h
index efd248c71..a38b59327 100644
--- a/include/cantera/thermo/ThermoPhase.h
+++ b/include/cantera/thermo/ThermoPhase.h
@@ -969,7 +969,7 @@ public:
      * @param x    Composition map of mole fractions. Species not in
      *             the composition map are assumed to have zero mole fraction
      */
-    virtual void setState_TPX(doublereal t, doublereal p, compositionMap& x);
+    virtual void setState_TPX(doublereal t, doublereal p, const compositionMap& x);
 
     //! Set the temperature (K), pressure (Pa), and mole fractions.
     /*!
@@ -1005,7 +1005,7 @@ public:
      * @param y    Composition map of mass fractions. Species not in
      *             the composition map are assumed to have zero mass fraction
      */
-    virtual void setState_TPY(doublereal t, doublereal p, compositionMap& y);
+    virtual void setState_TPY(doublereal t, doublereal p, const compositionMap& y);
 
     //! Set the internally stored temperature (K), pressure (Pa), and mass fractions of the phase
     /*!
diff --git a/src/equil/MultiPhase.cpp b/src/equil/MultiPhase.cpp
index b42efc674..62ded410f 100644
--- a/src/equil/MultiPhase.cpp
+++ b/src/equil/MultiPhase.cpp
@@ -433,15 +433,14 @@ void MultiPhase::setPhaseMoleFractions(const size_t n, const doublereal* const x
     }
 }
 
-void MultiPhase::setMolesByName(compositionMap& xMap)
+void MultiPhase::setMolesByName(const compositionMap& xMap)
 {
     size_t kk = nSpecies();
-    doublereal x;
     vector_fp moles(kk, 0.0);
     for (size_t k = 0; k < kk; k++) {
-        x = xMap[speciesName(k)];
-        if (x > 0.0) {
-            moles[k] = x;
+        compositionMap::const_iterator iter = xMap.find(speciesName(k));
+        if (iter != xMap.end() && iter->second > 0.0) {
+            moles[k] = iter->second;
         }
     }
     setMoles(DATA_PTR(moles));
diff --git a/src/thermo/MolalityVPSSTP.cpp b/src/thermo/MolalityVPSSTP.cpp
index 11cfdaf63..e6d060626 100644
--- a/src/thermo/MolalityVPSSTP.cpp
+++ b/src/thermo/MolalityVPSSTP.cpp
@@ -178,7 +178,7 @@ void MolalityVPSSTP::setMolalities(const doublereal* const molal)
     calcMolalities();
 }
 
-void MolalityVPSSTP::setMolalitiesByName(compositionMap& mMap)
+void MolalityVPSSTP::setMolalitiesByName(const compositionMap& mMap)
 {
     /*
      *  HKM -> Might need to be more complicated here, setting
@@ -186,7 +186,6 @@ void MolalityVPSSTP::setMolalitiesByName(compositionMap& mMap)
      *         preserved.
      */
     size_t kk = nSpecies();
-    doublereal x;
     /*
      * Get a vector of mole fractions
      */
@@ -194,14 +193,10 @@ void MolalityVPSSTP::setMolalitiesByName(compositionMap& mMap)
     getMoleFractions(DATA_PTR(mf));
     double xmolS = mf[m_indexSolvent];
     double xmolSmin = std::max(xmolS, m_xmolSolventMIN);
-    compositionMap::iterator p;
     for (size_t k = 0; k < kk; k++) {
-        p = mMap.find(speciesName(k));
-        if (p != mMap.end()) {
-            x = mMap[speciesName(k)];
-            if (x > 0.0) {
-                mf[k] = x * m_Mnaught * xmolSmin;
-            }
+        compositionMap::const_iterator iter = mMap.find(speciesName(k));
+        if (iter != mMap.end() && iter->second > 0.0) {
+            mf[k] = iter->second * m_Mnaught * xmolSmin;
         }
     }
     /*
@@ -403,7 +398,7 @@ void MolalityVPSSTP::setState_TPM(doublereal t, doublereal p,
     setState_TP(t, p);
 }
 
-void MolalityVPSSTP::setState_TPM(doublereal t, doublereal p, compositionMap& m)
+void MolalityVPSSTP::setState_TPM(doublereal t, doublereal p, const compositionMap& m)
 {
     setMolalitiesByName(m);
     setState_TP(t, p);
diff --git a/src/thermo/Phase.cpp b/src/thermo/Phase.cpp
index ae77b5dbc..099aff0bf 100644
--- a/src/thermo/Phase.cpp
+++ b/src/thermo/Phase.cpp
@@ -344,15 +344,14 @@ void Phase::setMoleFractions_NoNorm(const doublereal* const x)
     m_stateNum++;
 }
 
-void Phase::setMoleFractionsByName(compositionMap& xMap)
+void Phase::setMoleFractionsByName(const compositionMap& xMap)
 {
     size_t kk = nSpecies();
-    doublereal x;
     vector_fp mf(kk, 0.0);
     for (size_t k = 0; k < kk; k++) {
-        x = xMap[speciesName(k)];
-        if (x > 0.0) {
-            mf[k] = x;
+        compositionMap::const_iterator iter = xMap.find(speciesName(k));
+        if (iter != xMap.end() && iter->second > 0.0) {
+            mf[k] = iter->second;
         }
     }
     setMoleFractions(&mf[0]);
@@ -389,15 +388,14 @@ void Phase::setMassFractions_NoNorm(const doublereal* const y)
     m_stateNum++;
 }
 
-void Phase::setMassFractionsByName(compositionMap& yMap)
+void Phase::setMassFractionsByName(const compositionMap& yMap)
 {
     size_t kk = nSpecies();
-    doublereal y;
     vector_fp mf(kk, 0.0);
     for (size_t k = 0; k < kk; k++) {
-        y = yMap[speciesName(k)];
-        if (y > 0.0) {
-            mf[k] = y;
+        compositionMap::const_iterator iter = yMap.find(speciesName(k));
+        if (iter != yMap.end() && iter->second > 0.0) {
+            mf[k] = iter->second;
         }
     }
     setMassFractions(&mf[0]);
@@ -423,7 +421,7 @@ void Phase::setState_TNX(doublereal t, doublereal n, const doublereal* x)
     setMolarDensity(n);
 }
 
-void Phase::setState_TRX(doublereal t, doublereal dens, compositionMap& x)
+void Phase::setState_TRX(doublereal t, doublereal dens, const compositionMap& x)
 {
     setMoleFractionsByName(x);
     setTemperature(t);
@@ -437,7 +435,7 @@ void Phase::setState_TRY(doublereal t, doublereal dens, const doublereal* y)
     setDensity(dens);
 }
 
-void Phase::setState_TRY(doublereal t, doublereal dens, compositionMap& y)
+void Phase::setState_TRY(doublereal t, doublereal dens, const compositionMap& y)
 {
     setMassFractionsByName(y);
     setTemperature(t);
diff --git a/src/thermo/SingleSpeciesTP.cpp b/src/thermo/SingleSpeciesTP.cpp
index 869021b34..eac3fe666 100644
--- a/src/thermo/SingleSpeciesTP.cpp
+++ b/src/thermo/SingleSpeciesTP.cpp
@@ -247,7 +247,7 @@ void SingleSpeciesTP::setState_TPX(doublereal t, doublereal p,
 }
 
 void SingleSpeciesTP::setState_TPX(doublereal t, doublereal p,
-                                   compositionMap& x)
+                                   const compositionMap& x)
 {
     setTemperature(t);
     setPressure(p);
@@ -268,7 +268,7 @@ void SingleSpeciesTP::setState_TPY(doublereal t, doublereal p,
 }
 
 void SingleSpeciesTP::setState_TPY(doublereal t, doublereal p,
-                                   compositionMap& y)
+                                   const compositionMap& y)
 {
     setTemperature(t);
     setPressure(p);
diff --git a/src/thermo/ThermoPhase.cpp b/src/thermo/ThermoPhase.cpp
index 390d191d7..b6dd71083 100644
--- a/src/thermo/ThermoPhase.cpp
+++ b/src/thermo/ThermoPhase.cpp
@@ -139,7 +139,7 @@ void ThermoPhase::setState_TPX(doublereal t, doublereal p, const doublereal* x)
     setState_TP(t,p);
 }
 
-void ThermoPhase::setState_TPX(doublereal t, doublereal p, compositionMap& x)
+void ThermoPhase::setState_TPX(doublereal t, doublereal p, const compositionMap& x)
 {
     setMoleFractionsByName(x);
     setState_TP(t,p);
@@ -158,7 +158,7 @@ void ThermoPhase::setState_TPY(doublereal t, doublereal p, const doublereal* y)
     setState_TP(t,p);
 }
 
-void ThermoPhase::setState_TPY(doublereal t, doublereal p, compositionMap& y)
+void ThermoPhase::setState_TPY(doublereal t, doublereal p, const compositionMap& y)
 {
     setMassFractionsByName(y);
     setState_TP(t,p);