diff --git a/include/cantera/transport/GasTransport.h b/include/cantera/transport/GasTransport.h
index 4def843c5..49404c55b 100644
--- a/include/cantera/transport/GasTransport.h
+++ b/include/cantera/transport/GasTransport.h
@@ -133,7 +133,7 @@ protected:
     virtual void updateDiff_T();
 
     //! Vector of species mole fractions. These are processed so that all mole
-    //! fractions are >= MIN_X. Length = m_kk.
+    //! fractions are >= *Tiny*. Length = m_kk.
     vector_fp m_molefracs;
 
     //! Internal storage for the viscosity of the mixture  (kg /m /s)
diff --git a/include/cantera/transport/LiquidTransport.h b/include/cantera/transport/LiquidTransport.h
index 236869958..62af53af6 100644
--- a/include/cantera/transport/LiquidTransport.h
+++ b/include/cantera/transport/LiquidTransport.h
@@ -1200,7 +1200,7 @@ private:
     //! Local copy of the mass fractions of the species in the phase
     /**
      * This version of the mass fraction vector is adjusted to a
-     * minimum lower bound of MIN_X for use in transport calculations.
+     * minimum lower bound of *Tiny* for use in transport calculations.
      */
     vector_fp m_massfracs_tran;
 
@@ -1218,7 +1218,7 @@ private:
 
     //! Non-zero mole fraction vector used in transport property calculations
     /*!
-     *  The mole fractions here are assumed to be bounded by MIN_X and 1.0
+     *  The mole fractions here are assumed to be bounded by *Tiny* and 1.0
      *  and they may not be assumed to add up to one. This
      *  mole fraction vector is created from the ThermoPhase object.
      *  Derivative quantities of this use the _tran suffix.
diff --git a/src/equil/MultiPhaseEquil.cpp b/src/equil/MultiPhaseEquil.cpp
index b361a7e98..6401e3eea 100644
--- a/src/equil/MultiPhaseEquil.cpp
+++ b/src/equil/MultiPhaseEquil.cpp
@@ -16,8 +16,6 @@ using namespace std;
 namespace Cantera
 {
 
-const doublereal TINY = 1.0e-20;
-
 #if defined(WITH_HTML_LOGS)
 /// Used to print reaction equations. Given a stoichiometric
 /// coefficient 'nu' and a chemical symbol 'sym', return a string
@@ -428,7 +426,7 @@ void MultiPhaseEquil::getComponents(const std::vector<size_t>& order)
         // Check for rows that are zero
         bool isZeroRow = true;
         for (k = m; k < nColumns; k++) {
-            if (fabs(m_A(m,k)) > sqrt(TINY)) {
+            if (fabs(m_A(m,k)) > sqrt(Tiny)) {
                 isZeroRow = false;
                 break;
             }
@@ -439,7 +437,7 @@ void MultiPhaseEquil::getComponents(const std::vector<size_t>& order)
             bool foundSwapCandidate = false;
             for (; n > m; n--) {
                 for (k = m; k < nColumns; k++) {
-                    if (fabs(m_A(n,k)) > sqrt(TINY)) {
+                    if (fabs(m_A(n,k)) > sqrt(Tiny)) {
                         foundSwapCandidate = true;
                         break;
                     }
@@ -713,7 +711,7 @@ stepComposition(int loglevel)
                 if (m_moles[k] < MAJOR_THRESHOLD) {
                     m_force = true;
                 }
-                omax = m_moles[k]*FCTR/(fabs(m_work[k]) + TINY);
+                omax = m_moles[k]*FCTR/(fabs(m_work[k]) + Tiny);
                 if (m_work[k] < 0.0 && omax < omegamax) {
                     omegamax = omax;
                     if (omegamax < 1.0e-5) {
@@ -785,7 +783,6 @@ doublereal MultiPhaseEquil::computeReactionSteps(vector_fp& dxi)
     index_t j, k, ik, kc, ip;
     doublereal stoich, nmoles, csum, term1, fctr, rfctr;
     vector_fp nu;
-    const doublereal TINY = 1.0e-20;
     doublereal grad = 0.0;
 
     dxi.resize(nFree());
@@ -827,13 +824,13 @@ doublereal MultiPhaseEquil::computeReactionSteps(vector_fp& dxi)
             for (k = 0; k < m_nel; k++) {
                 kc = m_order[k];
                 stoich = nu[kc];
-                nmoles = fabs(m_mix->speciesMoles(m_species[kc])) + TINY;
+                nmoles = fabs(m_mix->speciesMoles(m_species[kc])) + Tiny;
                 csum += stoich*stoich*m_dsoln[kc]/nmoles;
             }
 
             // noncomponent term
             kc = m_order[j + m_nel];
-            nmoles = fabs(m_mix->speciesMoles(m_species[kc])) + TINY;
+            nmoles = fabs(m_mix->speciesMoles(m_species[kc])) + Tiny;
             term1 = m_dsoln[kc]/nmoles;
 
             // sum over solution phases
@@ -850,11 +847,11 @@ doublereal MultiPhaseEquil::computeReactionSteps(vector_fp& dxi)
                             psum += stoich * stoich;
                         }
                     }
-                    sum -= psum / (fabs(m_mix->phaseMoles(ip)) + TINY);
+                    sum -= psum / (fabs(m_mix->phaseMoles(ip)) + Tiny);
                 }
             }
             rfctr = term1 + csum + sum;
-            if (fabs(rfctr) < TINY) {
+            if (fabs(rfctr) < Tiny) {
                 fctr = 1.0;
             } else {
                 fctr = 1.0/(term1 + csum + sum);
diff --git a/src/thermo/DebyeHuckel.cpp b/src/thermo/DebyeHuckel.cpp
index 8c3dd95b3..b88105144 100644
--- a/src/thermo/DebyeHuckel.cpp
+++ b/src/thermo/DebyeHuckel.cpp
@@ -657,7 +657,6 @@ getMolalityActivityCoefficients(doublereal* acMolality) const
 void DebyeHuckel::getChemPotentials(doublereal* mu) const
 {
     double xx;
-    const double xxSmall = 1.0E-150;
     /*
      * First get the standard chemical potentials in
      * molar form.
@@ -674,11 +673,11 @@ void DebyeHuckel::getChemPotentials(doublereal* mu) const
     double xmolSolvent = moleFraction(m_indexSolvent);
     for (size_t k = 0; k < m_kk; k++) {
         if (m_indexSolvent != k) {
-            xx = std::max(m_molalities[k], xxSmall);
+            xx = std::max(m_molalities[k], SmallNumber);
             mu[k] += RT * (log(xx) + m_lnActCoeffMolal[k]);
         }
     }
-    xx = std::max(xmolSolvent, xxSmall);
+    xx = std::max(xmolSolvent, SmallNumber);
     mu[m_indexSolvent] +=
         RT * (log(xx) + m_lnActCoeffMolal[m_indexSolvent]);
 }
diff --git a/src/thermo/HMWSoln.cpp b/src/thermo/HMWSoln.cpp
index cda293c3b..f3a6cbe93 100644
--- a/src/thermo/HMWSoln.cpp
+++ b/src/thermo/HMWSoln.cpp
@@ -1122,7 +1122,6 @@ getUnscaledMolalityActivityCoefficients(doublereal* acMolality) const
 void HMWSoln::getChemPotentials(doublereal* mu) const
 {
     double xx;
-    const double xxSmall = 1.0E-150;
     /*
      * First get the standard chemical potentials in
      * molar form.
@@ -1139,11 +1138,11 @@ void HMWSoln::getChemPotentials(doublereal* mu) const
     double xmolSolvent = moleFraction(m_indexSolvent);
     for (size_t k = 0; k < m_kk; k++) {
         if (m_indexSolvent != k) {
-            xx = std::max(m_molalities[k], xxSmall);
+            xx = std::max(m_molalities[k], SmallNumber);
             mu[k] += RT * (log(xx) + m_lnActCoeffMolal_Scaled[k]);
         }
     }
-    xx = std::max(xmolSolvent, xxSmall);
+    xx = std::max(xmolSolvent, SmallNumber);
     mu[m_indexSolvent] +=
         RT * (log(xx) + m_lnActCoeffMolal_Scaled[m_indexSolvent]);
 }
diff --git a/src/thermo/IdealMolalSoln.cpp b/src/thermo/IdealMolalSoln.cpp
index 65d73d707..1af5eee2d 100644
--- a/src/thermo/IdealMolalSoln.cpp
+++ b/src/thermo/IdealMolalSoln.cpp
@@ -28,9 +28,6 @@ using namespace ctml;
 namespace Cantera
 {
 
-//!  Small value to be used in cutoff expressions with logs
-static double xxSmall = 1.0E-150;
-
 /*
  * Default constructor
  */
@@ -615,7 +612,6 @@ getMolalityActivityCoefficients(doublereal* acMolality) const
 void IdealMolalSoln::getChemPotentials(doublereal* mu) const
 {
     double xx;
-    //const double xxSmall = 1.0E-150;
 
     // Assertion is made for speed
     AssertThrow(m_indexSolvent == 0, "solvent not the first species");
@@ -641,7 +637,7 @@ void IdealMolalSoln::getChemPotentials(doublereal* mu) const
     if (IMS_typeCutoff_ == 0 || xmolSolvent > 3.* IMS_X_o_cutoff_/2.0) {
 
         for (size_t k = 1; k < m_kk; k++) {
-            xx = std::max(m_molalities[k], xxSmall);
+            xx = std::max(m_molalities[k], SmallNumber);
             mu[k] += RT * log(xx);
         }
         /*
@@ -649,7 +645,7 @@ void IdealMolalSoln::getChemPotentials(doublereal* mu) const
          *  -> see my notes
          */
 
-        xx = std::max(xmolSolvent, xxSmall);
+        xx = std::max(xmolSolvent, SmallNumber);
         mu[m_indexSolvent] +=
             (RT * (xmolSolvent - 1.0) / xx);
     } else {
@@ -661,10 +657,10 @@ void IdealMolalSoln::getChemPotentials(doublereal* mu) const
 
 
         for (size_t k = 1; k < m_kk; k++) {
-            xx = std::max(m_molalities[k], xxSmall);
+            xx = std::max(m_molalities[k], SmallNumber);
             mu[k] += RT * (log(xx) + IMS_lnActCoeffMolal_[k]);
         }
-        xx = std::max(xmolSolvent, xxSmall);
+        xx = std::max(xmolSolvent, SmallNumber);
         mu[m_indexSolvent] +=
             RT * (log(xx) + IMS_lnActCoeffMolal_[m_indexSolvent]);
     }
diff --git a/src/thermo/IonsFromNeutralVPSSTP.cpp b/src/thermo/IonsFromNeutralVPSSTP.cpp
index 8f32ba6e6..2a5f8991e 100644
--- a/src/thermo/IonsFromNeutralVPSSTP.cpp
+++ b/src/thermo/IonsFromNeutralVPSSTP.cpp
@@ -31,7 +31,6 @@ using namespace std;
 namespace Cantera
 {
 
-static  const double xxSmall = 1.0E-150;
 //====================================================================================================================
 /*
  * Default constructor.
@@ -672,7 +671,7 @@ void IonsFromNeutralVPSSTP::getPartialMolarEntropies(doublereal* sbar) const
     s_update_dlnActCoeffdT();
 
     for (size_t k = 0; k < m_kk; k++) {
-        xx = std::max(moleFractions_[k], xxSmall);
+        xx = std::max(moleFractions_[k], SmallNumber);
         sbar[k] += - lnActCoeff_Scaled_[k] -log(xx) - T * dlnActCoeffdT_Scaled_[k];
     }
     /*
diff --git a/src/thermo/MargulesVPSSTP.cpp b/src/thermo/MargulesVPSSTP.cpp
index d88579939..06eacf0f3 100644
--- a/src/thermo/MargulesVPSSTP.cpp
+++ b/src/thermo/MargulesVPSSTP.cpp
@@ -23,7 +23,6 @@ using namespace std;
 namespace Cantera
 {
 
-static  const double xxSmall = 1.0E-150;
 /*
  * Default constructor.
  *
@@ -280,7 +279,7 @@ void MargulesVPSSTP::getChemPotentials(doublereal* mu) const
     s_update_lnActCoeff();
     doublereal RT = GasConstant * temperature();
     for (size_t k = 0; k < m_kk; k++) {
-        xx = std::max(moleFractions_[k], xxSmall);
+        xx = std::max(moleFractions_[k], SmallNumber);
         mu[k] += RT * (log(xx) + lnActCoeff_Scaled_[k]);
     }
 }
@@ -439,7 +438,7 @@ void MargulesVPSSTP::getPartialMolarEntropies(doublereal* sbar) const
     s_update_dlnActCoeff_dT();
 
     for (size_t k = 0; k < m_kk; k++) {
-        xx = std::max(moleFractions_[k], xxSmall);
+        xx = std::max(moleFractions_[k], SmallNumber);
         sbar[k] += - lnActCoeff_Scaled_[k] -log(xx) - T * dlnActCoeffdT_Scaled_[k];
     }
     /*
diff --git a/src/thermo/MixedSolventElectrolyte.cpp b/src/thermo/MixedSolventElectrolyte.cpp
index 7dd6950f0..1d0987ec0 100644
--- a/src/thermo/MixedSolventElectrolyte.cpp
+++ b/src/thermo/MixedSolventElectrolyte.cpp
@@ -24,7 +24,6 @@ using namespace std;
 namespace Cantera
 {
 
-static  const double xxSmall = 1.0E-150;
 /*
  * Default constructor.
  *
@@ -285,7 +284,7 @@ void MixedSolventElectrolyte::getChemPotentials(doublereal* mu) const
      */
     doublereal RT = GasConstant * temperature();
     for (size_t k = 0; k < m_kk; k++) {
-        xx = std::max(moleFractions_[k], xxSmall);
+        xx = std::max(moleFractions_[k], SmallNumber);
         mu[k] += RT * (log(xx) + lnActCoeff_Scaled_[k]);
     }
 }
@@ -444,7 +443,7 @@ void MixedSolventElectrolyte::getPartialMolarEntropies(doublereal* sbar) const
     s_update_dlnActCoeff_dT();
 
     for (size_t k = 0; k < m_kk; k++) {
-        xx = std::max(moleFractions_[k], xxSmall);
+        xx = std::max(moleFractions_[k], SmallNumber);
         sbar[k] += - lnActCoeff_Scaled_[k] -log(xx) - T * dlnActCoeffdT_Scaled_[k];
     }
     /*
diff --git a/src/thermo/MolarityIonicVPSSTP.cpp b/src/thermo/MolarityIonicVPSSTP.cpp
index ce97dc184..f978b22d8 100644
--- a/src/thermo/MolarityIonicVPSSTP.cpp
+++ b/src/thermo/MolarityIonicVPSSTP.cpp
@@ -27,7 +27,6 @@ using namespace std;
 
 namespace Cantera
 {
-static  const double xxSmall = 1.0E-150;
 //====================================================================================================================
 /*
  * Default constructor.
@@ -212,7 +211,7 @@ void MolarityIonicVPSSTP::getChemPotentials(doublereal* mu) const
      */
     doublereal RT = GasConstant * temperature();
     for (size_t k = 0; k < m_kk; k++) {
-        xx = std::max(moleFractions_[k], xxSmall);
+        xx = std::max(moleFractions_[k], SmallNumber);
         mu[k] += RT * (log(xx) + lnActCoeff_Scaled_[k]);
     }
 }
@@ -337,7 +336,7 @@ void MolarityIonicVPSSTP::getPartialMolarEntropies(doublereal* sbar) const
     s_update_dlnActCoeff_dT();
 
     for (size_t k = 0; k < m_kk; k++) {
-        xx = std::max(moleFractions_[k], xxSmall);
+        xx = std::max(moleFractions_[k], SmallNumber);
         sbar[k] += - lnActCoeff_Scaled_[k] -log(xx) - T * dlnActCoeffdT_Scaled_[k];
     }
     /*
diff --git a/src/thermo/PhaseCombo_Interaction.cpp b/src/thermo/PhaseCombo_Interaction.cpp
index 9169a1841..4105a4d99 100644
--- a/src/thermo/PhaseCombo_Interaction.cpp
+++ b/src/thermo/PhaseCombo_Interaction.cpp
@@ -20,7 +20,6 @@ using namespace std;
 namespace Cantera
 {
 
-static  const double xxSmall = 1.0E-150;
 //====================================================================================================================
 /*
  * Default constructor.
@@ -296,7 +295,7 @@ void PhaseCombo_Interaction::getChemPotentials(doublereal* mu) const
      */
     doublereal RT = GasConstant * temperature();
     for (size_t k = 0; k < m_kk; k++) {
-        xx = std::max(moleFractions_[k], xxSmall);
+        xx = std::max(moleFractions_[k], SmallNumber);
         mu[k] += RT * (log(xx) + lnActCoeff_Scaled_[k]);
     }
 }
@@ -454,7 +453,7 @@ void PhaseCombo_Interaction::getPartialMolarEntropies(doublereal* sbar) const
     s_update_dlnActCoeff_dT();
 
     for (size_t k = 0; k < m_kk; k++) {
-        xx = std::max(moleFractions_[k], xxSmall);
+        xx = std::max(moleFractions_[k], SmallNumber);
         sbar[k] += - lnActCoeff_Scaled_[k] - log(xx) - T * dlnActCoeffdT_Scaled_[k];
     }
     /*
@@ -654,7 +653,7 @@ void PhaseCombo_Interaction::s_update_lnActCoeff() const
         /*
          *  We never sample the end of the mole fraction domains
          */
-        xx = std::max(moleFractions_[iK], xxSmall);
+        xx = std::max(moleFractions_[iK], SmallNumber);
         /*
          *  First wipe out the ideal solution mixing term
          */
@@ -775,11 +774,11 @@ void  PhaseCombo_Interaction::getdlnActCoeffds(const doublereal dTds, const doub
         /*
          *  We never sample the end of the mole fraction domains
          */
-        xx = std::max(moleFractions_[iK], xxSmall);
+        xx = std::max(moleFractions_[iK], SmallNumber);
         /*
          *  First wipe out the ideal solution mixing term
          */
-        if (xx > xxSmall) {
+        if (xx > SmallNumber) {
             dlnActCoeffds[iK] += - 1.0 / xx;
         }
 
@@ -839,12 +838,12 @@ void PhaseCombo_Interaction::s_update_dlnActCoeff_dlnN_diag() const
         /*
          *  We never sample the end of the mole fraction domains
          */
-        xx = std::max(moleFractions_[iK], xxSmall);
+        xx = std::max(moleFractions_[iK], SmallNumber);
         /*
          *  First wipe out the ideal solution mixing term
          */
         // lnActCoeff_Scaled_[iK] = - log(xx);
-        if (xx > xxSmall) {
+        if (xx > SmallNumber) {
             dlnActCoeffdlnN_diag_[iK] = - 1.0 + xx;
         }
 
@@ -901,12 +900,12 @@ void PhaseCombo_Interaction::s_update_dlnActCoeff_dlnN() const
         /*
          *  We never sample the end of the mole fraction domains
          */
-        xx = std::max(moleFractions_[iK], xxSmall);
+        xx = std::max(moleFractions_[iK], SmallNumber);
 
         for (size_t iM = 0; iM < m_kk; iM++) {
             XM = moleFractions_[iM];
 
-            if (xx > xxSmall) {
+            if (xx > SmallNumber) {
                 delKM = 0.0;
                 if (iK == iM) {
                     delKM = 1.0;
diff --git a/src/thermo/RedlichKisterVPSSTP.cpp b/src/thermo/RedlichKisterVPSSTP.cpp
index 09cbf8584..6ea8484c9 100644
--- a/src/thermo/RedlichKisterVPSSTP.cpp
+++ b/src/thermo/RedlichKisterVPSSTP.cpp
@@ -24,7 +24,6 @@ using namespace std;
 namespace Cantera
 {
 
-static  const double xxSmall = 1.0E-150;
 //====================================================================================================================
 /*
  * Default constructor.
@@ -282,7 +281,7 @@ void RedlichKisterVPSSTP::getChemPotentials(doublereal* mu) const
      */
     doublereal RT = GasConstant * temperature();
     for (size_t k = 0; k < m_kk; k++) {
-        xx = std::max(moleFractions_[k], xxSmall);
+        xx = std::max(moleFractions_[k], SmallNumber);
         mu[k] += RT * (log(xx) + lnActCoeff_Scaled_[k]);
     }
 }
@@ -441,7 +440,7 @@ void RedlichKisterVPSSTP::getPartialMolarEntropies(doublereal* sbar) const
     s_update_dlnActCoeff_dT();
 
     for (size_t k = 0; k < m_kk; k++) {
-        xx = std::max(moleFractions_[k], xxSmall);
+        xx = std::max(moleFractions_[k], SmallNumber);
         sbar[k] += - lnActCoeff_Scaled_[k] -log(xx) - T * dlnActCoeffdT_Scaled_[k];
     }
     /*
diff --git a/src/transport/AqueousTransport.cpp b/src/transport/AqueousTransport.cpp
index a4335f7c8..68cd56657 100644
--- a/src/transport/AqueousTransport.cpp
+++ b/src/transport/AqueousTransport.cpp
@@ -20,12 +20,6 @@
 
 using namespace std;
 
-/**
- * Mole fractions below MIN_X will be set to MIN_X when computing
- * transport properties.
- */
-#define MIN_X 1.e-20
-
 namespace Cantera
 {
 
@@ -512,10 +506,10 @@ void AqueousTransport::update_C()
     m_thermo->getMoleFractions(DATA_PTR(m_molefracs));
 
     // add an offset to avoid a pure species condition or
-    // negative mole fractions. MIN_X is 1.0E-20, a value
+    // negative mole fractions. *Tiny* is 1.0E-20, a value
     // which is below the additive machine precision of mole fractions.
     for (size_t k = 0; k < m_nsp; k++) {
-        m_molefracs[k] = std::max(MIN_X, m_molefracs[k]);
+        m_molefracs[k] = std::max(Tiny, m_molefracs[k]);
     }
 }
 //====================================================================================================================
diff --git a/src/transport/DustyGasTransport.cpp b/src/transport/DustyGasTransport.cpp
index 1262f86d7..98485945d 100644
--- a/src/transport/DustyGasTransport.cpp
+++ b/src/transport/DustyGasTransport.cpp
@@ -16,12 +16,6 @@
 
 using namespace std;
 
-/**
- * Mole fractions below MIN_X will be set to MIN_X when computing
- * transport properties.
- */
-#define MIN_X 1.e-20
-
 namespace Cantera
 {
 
@@ -441,7 +435,7 @@ void DustyGasTransport::updateTransport_C()
     // add an offset to avoid a pure species condition
     // (check - this may be unnecessary)
     for (size_t k = 0; k < m_nsp; k++) {
-        m_x[k] = std::max(MIN_X, m_x[k]);
+        m_x[k] = std::max(Tiny, m_x[k]);
     }
     // diffusion coeffs depend on Pressure
     m_bulk_ok = false;
diff --git a/src/transport/LiquidTransport.cpp b/src/transport/LiquidTransport.cpp
index ef50596bd..c9e203601 100644
--- a/src/transport/LiquidTransport.cpp
+++ b/src/transport/LiquidTransport.cpp
@@ -16,13 +16,6 @@
 
 using namespace std;
 
-/**
- * Mole fractions below MIN_X will be set to MIN_X when computing
- * transport properties.
- */
-#define MIN_X 1.e-14
-
-
 namespace Cantera
 {
 
@@ -1342,8 +1335,8 @@ bool LiquidTransport::update_C()
         concTot_tran_ = 0.0;
         for (size_t k = 0; k < m_nsp; k++) {
             m_molefracs[k] = std::max(0.0, m_molefracs[k]);
-            m_molefracs_tran[k] = std::max(MIN_X, m_molefracs[k]);
-            m_massfracs_tran[k] = std::max(MIN_X, m_massfracs[k]);
+            m_molefracs_tran[k] = std::max(Tiny, m_molefracs[k]);
+            m_massfracs_tran[k] = std::max(Tiny, m_massfracs[k]);
             concTot_tran_ += m_molefracs_tran[k];
             concTot_ += m_concentrations[k];
         }
diff --git a/src/transport/MixTransport.cpp b/src/transport/MixTransport.cpp
index fec6d70c8..bdcd40fdf 100644
--- a/src/transport/MixTransport.cpp
+++ b/src/transport/MixTransport.cpp
@@ -15,14 +15,6 @@
 #include <iostream>
 using namespace std;
 
-/**
- * Mole fractions below MIN_X will be set to MIN_X when computing
- * transport properties.
- */
-#ifndef MIN_X
-#define MIN_X 1.e-20
-#endif
-
 namespace Cantera
 {
 
@@ -270,7 +262,7 @@ void MixTransport::update_C()
 
     // add an offset to avoid a pure species condition
     for (size_t k = 0; k < m_nsp; k++) {
-        m_molefracs[k] = std::max(MIN_X, m_molefracs[k]);
+        m_molefracs[k] = std::max(Tiny, m_molefracs[k]);
     }
 }
 //====================================================================================================================
diff --git a/src/transport/MultiTransport.cpp b/src/transport/MultiTransport.cpp
index 9fcd79e00..84e9a5b93 100644
--- a/src/transport/MultiTransport.cpp
+++ b/src/transport/MultiTransport.cpp
@@ -25,12 +25,6 @@
 #include <iostream>
 using namespace std;
 
-/**
- * Mole fractions below MIN_X will be set to MIN_X when computing
- * transport properties.
- */
-#define MIN_X 1.e-20
-
 namespace Cantera
 {
 
@@ -578,7 +572,7 @@ void MultiTransport::update_C()
     // add an offset to avoid a pure species condition
     // (check - this may be unnecessary)
     for (size_t k = 0; k < m_nsp; k++) {
-        m_molefracs[k] = std::max(MIN_X, m_molefracs[k]);
+        m_molefracs[k] = std::max(Tiny, m_molefracs[k]);
     }
 }
 
diff --git a/src/transport/PecosTransport.cpp b/src/transport/PecosTransport.cpp
index a2bf9b658..63374f4c2 100755
--- a/src/transport/PecosTransport.cpp
+++ b/src/transport/PecosTransport.cpp
@@ -17,12 +17,6 @@
 #include <iostream>
 using namespace std;
 
-/**
- * Mole fractions below MIN_X will be set to MIN_X when computing
- * transport properties.
- */
-#define MIN_X 1.e-20
-
 namespace Cantera
 {
 
@@ -481,7 +475,7 @@ void PecosTransport::update_C()
     // add an offset to avoid a pure species condition
     int k;
     for (k = 0; k < m_nsp; k++) {
-        m_molefracs[k] = std::max(MIN_X, m_molefracs[k]);
+        m_molefracs[k] = std::max(Tiny, m_molefracs[k]);
     }
 }
 
diff --git a/src/transport/SimpleTransport.cpp b/src/transport/SimpleTransport.cpp
index 4b040e34d..f0fb89f5d 100644
--- a/src/transport/SimpleTransport.cpp
+++ b/src/transport/SimpleTransport.cpp
@@ -14,13 +14,6 @@
 #include <iostream>
 using namespace std;
 
-/**
- * Mole fractions below MIN_X will be set to MIN_X when computing
- * transport properties.
- */
-#define MIN_X 1.e-14
-
-
 #ifndef SAFE_DELETE
 //! \cond
 #define SAFE_DELETE(x)  if (x) { delete (x); x = 0; }
diff --git a/src/transport/TransportBase.cpp b/src/transport/TransportBase.cpp
index d1a1a3c93..fc339d553 100644
--- a/src/transport/TransportBase.cpp
+++ b/src/transport/TransportBase.cpp
@@ -16,13 +16,6 @@
 #include <iostream>
 using namespace std;
 
-/**
- * Mole fractions below MIN_X will be set to MIN_X when computing
- * transport properties.
- */
-#define MIN_X 1.e-20
-
-
 namespace Cantera
 {