diff --git a/src/reactions/exampleSystems/BulkGeneric.hpp b/src/reactions/exampleSystems/BulkGeneric.hpp
index 77547ce..7f1eedd 100644
--- a/src/reactions/exampleSystems/BulkGeneric.hpp
+++ b/src/reactions/exampleSystems/BulkGeneric.hpp
@@ -45,7 +45,7 @@ namespace bulkGeneric
 //   um1Constants };
 
 
-using simpleKineticTestType = reactionsSystems::MixedReactionsParameters< double, int, int, 5, 2, 0 >;
+using simpleKineticTestType = reactionsSystems::MixedReactionsParameters< double, int, signed char, 5, 2, 0 >;
 
 constexpr 
 simpleKineticTestType
@@ -68,7 +68,7 @@ simpleKineticTestRateParams =
   0
 };
 
-using simpleTestType = reactionsSystems::MixedReactionsParameters< double, int, int, 5, 2, 2 >;
+using simpleTestType = reactionsSystems::MixedReactionsParameters< double, int, signed char, 5, 2, 2 >;
 
 constexpr 
 simpleTestType
diff --git a/src/reactions/exampleSystems/ChainGeneric.hpp b/src/reactions/exampleSystems/ChainGeneric.hpp
index 8b0acd8..196246f 100644
--- a/src/reactions/exampleSystems/ChainGeneric.hpp
+++ b/src/reactions/exampleSystems/ChainGeneric.hpp
@@ -19,7 +19,7 @@ namespace ChainGeneric
 {
 // *****UNCRUSTIFY-OFF******
 
-  using serialAllKineticType = reactionsSystems::MixedReactionsParameters< double, int, int, 3, 3, 0 >;
+  using serialAllKineticType = reactionsSystems::MixedReactionsParameters< double, int, signed char, 3, 3, 0 >;
 
   constexpr serialAllKineticType serialAllKineticParams =
   {
diff --git a/src/reactions/exampleSystems/MoMasBenchmark.hpp b/src/reactions/exampleSystems/MoMasBenchmark.hpp
index c0c8f06..3a871b4 100644
--- a/src/reactions/exampleSystems/MoMasBenchmark.hpp
+++ b/src/reactions/exampleSystems/MoMasBenchmark.hpp
@@ -19,8 +19,8 @@ namespace MoMasBenchmark
 {
 // *****UNCRUSTIFY-OFF******
 
-  using easyCaseType = reactionsSystems::MixedReactionsParameters< double, int, int, 12, 7, 7 >;
-  using mediumCaseType = reactionsSystems::MixedReactionsParameters< double, int, int, 14, 10, 9 >; 
+  using easyCaseType = reactionsSystems::MixedReactionsParameters< double, int, signed char, 12, 7, 7 >;
+  using mediumCaseType = reactionsSystems::MixedReactionsParameters< double, int, signed char, 14, 10, 9 >; 
 
   constexpr easyCaseType easyCaseParams =
 {
diff --git a/src/reactions/geochemistry/Carbonate.hpp b/src/reactions/geochemistry/Carbonate.hpp
index 52ae3ab..50d8b05 100644
--- a/src/reactions/geochemistry/Carbonate.hpp
+++ b/src/reactions/geochemistry/Carbonate.hpp
@@ -24,7 +24,7 @@ namespace geochemistry
 namespace carbonate
 {
 
-constexpr CArrayWrapper<double, 10, 17> stoichMatrix = 
+constexpr CArrayWrapper<signed char, 10, 17> stoichMatrix = 
   { //   OH-    CO2  CO3-2  CaHCO3+   CaSO4  CaCl+  CaCl2  MgSO4   NaSO4- CaCO3  H+  HCO3-  Ca+2    SO4-2    Cl-    Mg+2  Na+
     {    -1,     0,     0,      0,     0,     0,     0,     0,     0,     0,    -1,     0,     0,     0,     0,     0,     0  }, //     OH- + H+ = H2O         
     {     0,    -1,     0,      0,     0,     0,     0,     0,     0,     0,     1,     1,     0,     0,     0,     0,     0  }, //    CO2 + H2O = H+ + HCO3-  
@@ -38,7 +38,7 @@ constexpr CArrayWrapper<double, 10, 17> stoichMatrix =
     {     0,     0,     0,      0,     0,     0,     0,     0,     0,    -1,    -1,     1,     1,     0,     0,     0,     0  }  //   CaCO3(s) + H+ = Ca+2 + HCO3- (kinetic)
   };
 
-constexpr CArrayWrapper<double, 10, 16> stoichMatrixNosolid = 
+constexpr CArrayWrapper<signed char, 10, 16> stoichMatrixNosolid = 
   { //   OH-    CO2  CO3-2  CaHCO3+   CaSO4  CaCl+  CaCl2  MgSO4   NaSO4-  H+  HCO3-  Ca+2    SO4-2    Cl-    Mg+2  Na+
     {    -1,     0,     0,      0,     0,     0,     0,     0,     0,     -1,     0,     0,     0,     0,     0,     0  }, //     OH- + H+ = H2O         
     {     0,    -1,     0,      0,     0,     0,     0,     0,     0,      1,     1,     0,     0,     0,     0,     0  }, //    CO2 + H2O = H+ + HCO3-  
@@ -109,9 +109,9 @@ constexpr CArrayWrapper<int, 10> mobileSpeciesFlag =
 
 }
 
-using carbonateSystemAllKineticType     = reactionsSystems::MixedReactionsParameters< double, int, int, 17, 10, 0 >;
-using carbonateSystemAllEquilibriumType = reactionsSystems::MixedReactionsParameters< double, int, int, 17, 10, 10 >;
-using carbonateSystemType               = reactionsSystems::MixedReactionsParameters< double, int, int, 16, 10, 9 >;
+using carbonateSystemAllKineticType     = reactionsSystems::MixedReactionsParameters< double, int, signed char, 17, 10, 0 >;
+using carbonateSystemAllEquilibriumType = reactionsSystems::MixedReactionsParameters< double, int, signed char, 17, 10, 10 >;
+using carbonateSystemType               = reactionsSystems::MixedReactionsParameters< double, int, signed char, 16, 10, 9 >;
 
 constexpr carbonateSystemAllKineticType carbonateSystemAllKinetic( carbonate::stoichMatrix, carbonate::equilibriumConstants, carbonate::forwardRates, carbonate::reverseRates, carbonate::mobileSpeciesFlag, 0 );
 constexpr carbonateSystemAllEquilibriumType carbonateSystemAllEquilibrium( carbonate::stoichMatrix, carbonate::equilibriumConstants, carbonate::forwardRates, carbonate::reverseRates, carbonate::mobileSpeciesFlag );
diff --git a/src/reactions/geochemistry/Forge.hpp b/src/reactions/geochemistry/Forge.hpp
index 276577c..e599389 100644
--- a/src/reactions/geochemistry/Forge.hpp
+++ b/src/reactions/geochemistry/Forge.hpp
@@ -25,7 +25,7 @@ namespace forge
    // Stoichiometric matrix [13 reactions × 23 species]
    // Columns 0–12: secondary species (must be -1 on diagonal)
    // Columns 13–22: primary species
-constexpr CArrayWrapper< double, 19, 26 > soichMatrix = 
+constexpr CArrayWrapper< signed char, 19, 26 > soichMatrix = 
 {// CaCO₃  CaHCO₃⁺ CaSO₄ CaCl⁺ CaCl₂ MgHCO₃⁺ MgCO₃ MgCl⁺ CO₂(aq) HSO₄⁻ KHSO₄ HSiO₃⁻ NaHSilO₃ NaCl  KCl  KSO₄⁻ | H⁺  Ca²⁺  Mg²⁺   Na⁺    K⁺   Al³⁺   HCO₃⁻  SO₄²⁻  Cl⁻  SiO₂(aq)
   { -1,     0,     0,    0,    0,     0,     0,    0,     0,     0,     0,     0,     0,     0,   0,    0,     -1,   1,    0,     0,    0,    0,     1,     0,     0,   0  }, // CaCO₃(aq) + H⁺ ⇌ Ca²⁺ + HCO₃⁻
   {  0,    -1,     0,    0,    0,     0,     0,    0,     0,     0,     0,     0,     0,     0,   0,    0,      0,   1,    0,     0,    0,    0,     1,     0,     0,   0  }, // CaHCO₃⁺ ⇌ Ca²⁺ + HCO₃⁻
@@ -144,7 +144,7 @@ constexpr CArrayWrapper< int, 19 > mobileSpeciesFlag =
 
 }
 
-using forgeSystemType = reactionsSystems::MixedReactionsParameters< double, int, int, 26, 19, 16 >;
+using forgeSystemType = reactionsSystems::MixedReactionsParameters< double, int, signed char, 26, 19, 16 >;
 
 
 constexpr forgeSystemType forgeSystem( forge::soichMatrix, forge::equilibriumConstants, forge::fwRateConstant, forge::reverseRateConstant, forge::mobileSpeciesFlag );
diff --git a/src/reactions/geochemistry/Ultramafics.hpp b/src/reactions/geochemistry/Ultramafics.hpp
index d69d517..d993536 100644
--- a/src/reactions/geochemistry/Ultramafics.hpp
+++ b/src/reactions/geochemistry/Ultramafics.hpp
@@ -25,7 +25,7 @@ namespace geochemistry
 namespace ultramafics
 {
 
-constexpr CArrayWrapper<double, 21, 25> stoichMatrix = 
+constexpr CArrayWrapper<signed char, 21, 25> stoichMatrix = 
 { //      OH-   CO2(aq)      CO3--      Mg2OH+++   Mg4(OH)++++   MgOH+   Mg2CO3++   MgCO3(aq)   MgHCO3+   Mg(H3SiO4)2      MgH2SiO4     MgH3SiO4+   H2SiO4--   H3SiO4-      H4(H2SiO4)----   H6(H2SiO4)--   Mg2SiO4   MgCO3   SiO2    Mg3Si2O5(OH)4     Mg(OH)2     H+      HCO3-      Mg++   SiO2(aq)  
     {    -1,         0,       0,          0,          0,       0,          0,           0,         0,             0,          0,           0,          0,         0,            0,              0,         0,       0,         0,           0,           0,        -1,       0,        0,        0   }, //  OH- + H+ = H2O          
     {     0,        -1,       0,          0,          0,       0,          0,           0,         0,             0,          0,           0,          0,         0,            0,              0,         0,       0,         0,           0,           0,         1,       1,        0,        0   }, //  CO2(aq) + H2O = HCO3- + H+   
@@ -153,9 +153,9 @@ constexpr CArrayWrapper<int, 21> mobileSpeciesFlag =
   };
 }
 
-  using ultramaficSystemAllKineticType     = reactionsSystems::MixedReactionsParameters< double, int, int, 25, 21, 0 >;
-  using ultramaficSystemAllEquilibriumType = reactionsSystems::MixedReactionsParameters< double, int, int, 25, 21, 21 >;
-  using ultramaficSystemType               = reactionsSystems::MixedReactionsParameters< double, int, int, 25, 21, 16 >;
+  using ultramaficSystemAllKineticType     = reactionsSystems::MixedReactionsParameters< double, int, signed char, 25, 21, 0 >;
+  using ultramaficSystemAllEquilibriumType = reactionsSystems::MixedReactionsParameters< double, int, signed char, 25, 21, 21 >;
+  using ultramaficSystemType               = reactionsSystems::MixedReactionsParameters< double, int, signed char, 25, 21, 16 >;
 
   constexpr ultramaficSystemAllKineticType     ultramaficSystemAllKinetic( ultramafics::stoichMatrix, ultramafics::equilibriumConstants, ultramafics::forwardRates, ultramafics::reverseRates, ultramafics::mobileSpeciesFlag );
   constexpr ultramaficSystemAllEquilibriumType ultramaficSystemAllEquilibrium( ultramafics::stoichMatrix, ultramafics::equilibriumConstants, ultramafics::forwardRates, ultramafics::reverseRates, ultramafics::mobileSpeciesFlag );
diff --git a/src/reactions/reactionsSystems/Parameters.hpp b/src/reactions/reactionsSystems/Parameters.hpp
index 54cddaa..3532481 100644
--- a/src/reactions/reactionsSystems/Parameters.hpp
+++ b/src/reactions/reactionsSystems/Parameters.hpp
@@ -53,7 +53,7 @@ struct EquilibriumReactionsParameters
 
   HPCREACT_HOST_DEVICE
   constexpr
-  EquilibriumReactionsParameters( CArrayWrapper< RealType, NUM_REACTIONS, NUM_SPECIES > const & stoichiometricMatrix,
+  EquilibriumReactionsParameters( CArrayWrapper< IndexType, NUM_REACTIONS, NUM_SPECIES > const & stoichiometricMatrix,
                                   CArrayWrapper< RealType, NUM_REACTIONS > equilibriumConstant,
                                   CArrayWrapper< IntType, NUM_REACTIONS > mobileSecondarySpeciesFlag ):
     m_stoichiometricMatrix( stoichiometricMatrix ),
@@ -62,11 +62,11 @@ struct EquilibriumReactionsParameters
   {}
 
 
-  HPCREACT_HOST_DEVICE RealType stoichiometricMatrix( IndexType const r, int const i ) const { return m_stoichiometricMatrix[r][i]; }
+  HPCREACT_HOST_DEVICE IndexType stoichiometricMatrix( IndexType const r, int const i ) const { return m_stoichiometricMatrix[r][i]; }
   HPCREACT_HOST_DEVICE RealType equilibriumConstant( IndexType const r ) const { return m_equilibriumConstant[r]; }
   HPCREACT_HOST_DEVICE IntType mobileSecondarySpeciesFlag( IndexType const r ) const { return m_mobileSecondarySpeciesFlag[r]; }
 
-  CArrayWrapper< RealType, NUM_REACTIONS, NUM_SPECIES > m_stoichiometricMatrix;
+  CArrayWrapper< IndexType, NUM_REACTIONS, NUM_SPECIES > m_stoichiometricMatrix;
   CArrayWrapper< RealType, NUM_REACTIONS > m_equilibriumConstant;
   CArrayWrapper< IntType, NUM_REACTIONS > m_mobileSecondarySpeciesFlag;
 };
@@ -87,7 +87,7 @@ struct KineticReactionsParameters
   HPCREACT_HOST_DEVICE static constexpr IndexType numReactions() { return NUM_REACTIONS; }
 
   HPCREACT_HOST_DEVICE
-  constexpr KineticReactionsParameters( CArrayWrapper< RealType, NUM_REACTIONS, NUM_SPECIES > const & stoichiometricMatrix,
+  constexpr KineticReactionsParameters( CArrayWrapper< IndexType, NUM_REACTIONS, NUM_SPECIES > const & stoichiometricMatrix,
                                         CArrayWrapper< RealType, NUM_REACTIONS > const & rateConstantForward,
                                         CArrayWrapper< RealType, NUM_REACTIONS > const & rateConstantReverse,
                                         CArrayWrapper< RealType, NUM_REACTIONS > const & equilibriumConstant,
@@ -100,14 +100,14 @@ struct KineticReactionsParameters
   {}
 
 
-  HPCREACT_HOST_DEVICE RealType stoichiometricMatrix( IndexType const r, int const i ) const { return m_stoichiometricMatrix[r][i]; }
+  HPCREACT_HOST_DEVICE IndexType stoichiometricMatrix( IndexType const r, int const i ) const { return m_stoichiometricMatrix[r][i]; }
   HPCREACT_HOST_DEVICE RealType rateConstantForward( IndexType const r ) const { return m_rateConstantForward[r]; }
   HPCREACT_HOST_DEVICE RealType rateConstantReverse( IndexType const r ) const { return m_rateConstantReverse[r]; }
   HPCREACT_HOST_DEVICE RealType equilibriumConstant( IndexType const r ) const { return m_rateConstantForward[r] / m_rateConstantReverse[r]; }
 
   HPCREACT_HOST_DEVICE IntType reactionRatesUpdateOption() const { return m_reactionRatesUpdateOption; }
 
-  CArrayWrapper< RealType, NUM_REACTIONS, NUM_SPECIES > m_stoichiometricMatrix;
+  CArrayWrapper< IndexType, NUM_REACTIONS, NUM_SPECIES > m_stoichiometricMatrix;
   CArrayWrapper< RealType, NUM_REACTIONS > m_rateConstantForward;
   CArrayWrapper< RealType, NUM_REACTIONS > m_rateConstantReverse;
   CArrayWrapper< RealType, NUM_REACTIONS > m_equilibiriumConstant;
@@ -131,7 +131,7 @@ struct MixedReactionsParameters
 
   constexpr MixedReactionsParameters() = default;
 
-  constexpr MixedReactionsParameters( CArrayWrapper< RealType, NUM_REACTIONS, NUM_SPECIES > const & stoichiometricMatrix,
+  constexpr MixedReactionsParameters( CArrayWrapper< IndexType, NUM_REACTIONS, NUM_SPECIES > const & stoichiometricMatrix,
                                       CArrayWrapper< RealType, NUM_REACTIONS > const & equilibriumConstant,
                                       CArrayWrapper< RealType, NUM_REACTIONS > const & rateConstantForward,
                                       CArrayWrapper< RealType, NUM_REACTIONS > const & rateConstantReverse,
@@ -162,7 +162,7 @@ struct MixedReactionsParameters
   EquilibriumReactionsParameters< RealType, IntType, IndexType, numSpecies(), numEquilibriumReactions() >
   equilibriumReactionsParameters() const
   {
-    CArrayWrapper< RealType, numEquilibriumReactions(), numSpecies() > eqMatrix{};
+    CArrayWrapper< IndexType, numEquilibriumReactions(), numSpecies() > eqMatrix{};
     CArrayWrapper< RealType, numEquilibriumReactions() > eqConstants{};
     CArrayWrapper< IntType, numEquilibriumReactions() > mobileSpeciesFlags{};
 
@@ -184,7 +184,7 @@ struct MixedReactionsParameters
   KineticReactionsParameters< RealType, IntType, IndexType, numSpecies(), numKineticReactions() >
   kineticReactionsParameters() const
   {
-    CArrayWrapper< RealType, numKineticReactions(), numSpecies() > kineticMatrix{};
+    CArrayWrapper< IndexType, numKineticReactions(), numSpecies() > kineticMatrix{};
     CArrayWrapper< RealType, numKineticReactions() > rateConstantForward{};
     CArrayWrapper< RealType, numKineticReactions() > rateConstantReverse{};
     CArrayWrapper< RealType, numKineticReactions() > equilibriumConstant{};
@@ -239,12 +239,12 @@ struct MixedReactionsParameters
     }
   }
 
-  HPCREACT_HOST_DEVICE  RealType stoichiometricMatrix( IndexType const r, int const i ) const { return m_stoichiometricMatrix[r][i]; }
+  HPCREACT_HOST_DEVICE  IndexType stoichiometricMatrix( IndexType const r, int const i ) const { return m_stoichiometricMatrix[r][i]; }
   HPCREACT_HOST_DEVICE  RealType equilibriumConstant( IndexType const r ) const { return m_equilibriumConstant[r]; }
   HPCREACT_HOST_DEVICE  RealType rateConstantForward( IndexType const r ) const { return m_rateConstantForward[r]; }
   HPCREACT_HOST_DEVICE  RealType rateConstantReverse( IndexType const r ) const { return m_rateConstantReverse[r]; }
 
-  CArrayWrapper< RealType, NUM_REACTIONS, NUM_SPECIES > m_stoichiometricMatrix;
+  CArrayWrapper< IndexType, NUM_REACTIONS, NUM_SPECIES > m_stoichiometricMatrix;
   CArrayWrapper< RealType, NUM_REACTIONS > m_equilibriumConstant;
   CArrayWrapper< RealType, NUM_REACTIONS > m_rateConstantForward;
   CArrayWrapper< RealType, NUM_REACTIONS > m_rateConstantReverse;