diff --git a/include/cantera/thermo/Phase.h b/include/cantera/thermo/Phase.h
index 8de76a69f1..040616df5b 100644
--- a/include/cantera/thermo/Phase.h
+++ b/include/cantera/thermo/Phase.h
@@ -631,6 +631,8 @@ class Phase
     //! Returns a const pointer to the start of the moleFraction/MW array.
     //! This array is the array of mole fractions, each divided by the mean
     //! molecular weight.
+    //! @deprecated To be removed after Cantera 3.0. Generally replaceable by using
+    //!     getMoleFractions() and meanMolecularWeight().
     const double* moleFractdivMMW() const;
 
     //! Dimensionless electrical charge of a single molecule of species k
diff --git a/src/thermo/IdealSolidSolnPhase.cpp b/src/thermo/IdealSolidSolnPhase.cpp
index 06eb854e81..24b0860f35 100644
--- a/src/thermo/IdealSolidSolnPhase.cpp
+++ b/src/thermo/IdealSolidSolnPhase.cpp
@@ -51,13 +51,11 @@ doublereal IdealSolidSolnPhase::cp_mole() const
 void IdealSolidSolnPhase::calcDensity()
 {
     // Calculate the molarVolume of the solution (m**3 kmol-1)
-    const doublereal* const dtmp = moleFractdivMMW();
-    double invDens = dot(m_speciesMolarVolume.begin(),
-                         m_speciesMolarVolume.end(), dtmp);
+    double v_mol = mean_X(m_speciesMolarVolume);
 
-    // Set the density in the parent State object directly, by calling the
+    // Set the density in the parent object directly, by calling the
     // Phase::assignDensity() function.
-    Phase::assignDensity(1.0/invDens);
+    Phase::assignDensity(meanMolecularWeight()/v_mol);
 }
 
 void IdealSolidSolnPhase::setPressure(doublereal p)
@@ -86,23 +84,18 @@ Units IdealSolidSolnPhase::standardConcentrationUnits() const
 
 void IdealSolidSolnPhase::getActivityConcentrations(doublereal* c) const
 {
-    const doublereal* const dtmp = moleFractdivMMW();
-    const double mmw = meanMolecularWeight();
+    getMoleFractions(c);
     switch (m_formGC) {
     case 0:
-        for (size_t k = 0; k < m_kk; k++) {
-            c[k] = dtmp[k] * mmw;
-        }
         break;
     case 1:
         for (size_t k = 0; k < m_kk; k++) {
-            c[k] = dtmp[k] * mmw / m_speciesMolarVolume[k];
+            c[k] /= m_speciesMolarVolume[k];
         }
         break;
     case 2:
-        double atmp = mmw / m_speciesMolarVolume[m_kk-1];
         for (size_t k = 0; k < m_kk; k++) {
-            c[k] = dtmp[k] * atmp;
+            c[k] /= m_speciesMolarVolume[m_kk-1];
         }
         break;
     }
diff --git a/src/thermo/IdealSolnGasVPSS.cpp b/src/thermo/IdealSolnGasVPSS.cpp
index a91b52a875..1a46cbb68a 100644
--- a/src/thermo/IdealSolnGasVPSS.cpp
+++ b/src/thermo/IdealSolnGasVPSS.cpp
@@ -73,12 +73,9 @@ void IdealSolnGasVPSS::setPressure(doublereal p)
 
 void IdealSolnGasVPSS::calcDensity()
 {
-    const doublereal* const dtmp = moleFractdivMMW();
-    const vector_fp& vss = getStandardVolumes();
-    double dens = 1.0 / dot(vss.begin(), vss.end(), dtmp);
-
-    // Set the density in the parent State object directly
-    Phase::assignDensity(dens);
+    double v_mol = mean_X(getStandardVolumes());
+    // Set the density in the parent object directly
+    Phase::assignDensity(meanMolecularWeight() / v_mol);
 }
 
 Units IdealSolnGasVPSS::standardConcentrationUnits() const
diff --git a/src/thermo/Phase.cpp b/src/thermo/Phase.cpp
index 68a4a9428a..8278a14320 100644
--- a/src/thermo/Phase.cpp
+++ b/src/thermo/Phase.cpp
@@ -547,6 +547,8 @@ double Phase::moleFraction(const std::string& nameSpec) const
 
 const double* Phase::moleFractdivMMW() const
 {
+    warn_deprecated("Phase::moleFractdivMMW", "To be removed after Cantera 3.0. "
+        "Generally replaceable by 'getMoleFractions' and 'meanMolecularWeight'.");
     return &m_ym[0];
 }