diff --git a/src/thermophysicalModels/thermophysicalProperties/solidProperties/solidMixtureProperties/solidMixtureProperties.C b/src/thermophysicalModels/thermophysicalProperties/solidProperties/solidMixtureProperties/solidMixtureProperties.C
index df9a4c1f0c4fd5535a372dedebad58c752e335bf..18fa9faa7381cddad11cd1bbf0391ed4768d2b97 100644
--- a/src/thermophysicalModels/thermophysicalProperties/solidProperties/solidMixtureProperties/solidMixtureProperties.C
+++ b/src/thermophysicalModels/thermophysicalProperties/solidProperties/solidMixtureProperties/solidMixtureProperties.C
@@ -88,40 +88,29 @@ Foam::autoPtr<Foam::solidMixtureProperties> Foam::solidMixtureProperties::New
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-Foam::scalarField Foam::solidMixtureProperties::X(const scalarField& Y) const
+Foam::scalar Foam::solidMixtureProperties::rho(const scalarField& Y) const
 {
-    scalarField X(Y.size());
-    scalar rhoInv = 0.0;
-    forAll(X, i)
-    {
-        rhoInv += Y[i]/properties_[i].rho();
-        X[i] = Y[i]/properties_[i].rho();
-    }
-
-    tmp<scalarField> tfld(X/rhoInv);
-    return tfld();
-}
-
+    scalar rrho = 0;
 
-Foam::scalar Foam::solidMixtureProperties::rho(const scalarField& X) const
-{
-    scalar val = 0.0;
     forAll(properties_, i)
     {
-        val += properties_[i].rho()*X[i];
+        rrho += Y[i]/properties_[i].rho();
     }
-    return val;
+
+    return 1/rrho;
 }
 
 
 Foam::scalar Foam::solidMixtureProperties::Cp(const scalarField& Y) const
 {
-    scalar val = 0.0;
+    scalar Cp = 0;
+
     forAll(properties_, i)
     {
-        val += properties_[i].Cp()*Y[i];
+        Cp += Y[i]*properties_[i].Cp();
     }
-    return val;
+
+    return Cp;
 }
 
 
diff --git a/src/thermophysicalModels/thermophysicalProperties/solidProperties/solidMixtureProperties/solidMixtureProperties.H b/src/thermophysicalModels/thermophysicalProperties/solidProperties/solidMixtureProperties/solidMixtureProperties.H
index 2d34f771b8d3dcba9c385d0d98491a737931f602..a9cdfa732c24bd4d3c2bf2a430a325a57191f9e2 100644
--- a/src/thermophysicalModels/thermophysicalProperties/solidProperties/solidMixtureProperties/solidMixtureProperties.H
+++ b/src/thermophysicalModels/thermophysicalProperties/solidProperties/solidMixtureProperties/solidMixtureProperties.H
@@ -31,17 +31,11 @@ Description
     \verbatim
         <parentDictionary>
         {
-            C
-            {
-                defaultCoeffs   yes;     // employ default coefficients
-            }
+            C;
+
             ash
             {
-                defaultCoeffs   no;
-                ashCoeffs
-                {
-                    ... user defined properties for ash
-                }
+                //... user defined properties for ash
             }
         }
     \endverbatim
@@ -58,10 +52,9 @@ See also
 #ifndef solidMixtureProperties_H
 #define solidMixtureProperties_H
 
-#include "scalarField.H"
-#include "PtrList.H"
 #include "solidProperties.H"
-#include "autoPtr.H"
+#include "PtrList.H"
+#include "scalarField.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -134,19 +127,12 @@ public:
             return components_.size();
         }
 
-
-        //- Returns the mass fractions, given mole fractions
-        scalarField Y(const scalarField& X) const;
-
-        //- Returns the mole fractions, given mass fractions
-        scalarField X(const scalarField& Y) const;
-
         //- Calculate the mixture density [kg/m^3] as a function of
-        //  volume fractions
-        scalar rho(const scalarField& X) const;
+        //  mass fractions
+        scalar rho(const scalarField& Y) const;
 
-        //- Calculate the mixture heat capacity [J/(kg K)] as a function
-        //  of mass fractions
+        //- Calculate the mixture heat capacity [J/(kg K)] as a function of
+        //  mass fractions
         scalar Cp(const scalarField& Y) const;
 };