diff --git a/cython/specmicp/reaction_path.pyx b/cython/specmicp/reaction_path.pyx
index 2ad43a3..586cfe0 100644
--- a/cython/specmicp/reaction_path.pyx
+++ b/cython/specmicp/reaction_path.pyx
@@ -1,6 +1,36 @@
+from libcpp.pair cimport pair
+from libcpp.string cimport string
 from reaction_path cimport ReactionPathModel
+from database cimport Database
+from database import DatabaseManager
+
 
 cdef class ReactionPathSimulation:
+    """The simulation to solve"""
     cdef ReactionPathModel* thisptr
-    def __cinit__(self, database):
-        thisptr = new ReactionPathModel()
+    def __cinit__(self, thedatabase):
+        self.thisptr = new ReactionPathModel()
+        self.thedatabase = thedatabase
+    def add_aqueous_species(self,
+                           bytes label,
+                           float initial_amount, 
+                           float increase_amount):
+        """Add an aqueous system in the system"""
+        self.thisptr.amount_aqueous.insert(
+            pair[string, pair[float, float]](
+                label, 
+                pair[float, float](initial_amount, increase_amount)))
+    def add_mineral(self,
+                    bytes label,
+                    float initial_amount, 
+                    float increase_amount):
+        """Add a mineral in the system"""
+        self.thisptr.amount_minerals.insert(
+            pair[string, pair[float, float]](
+                label, 
+                pair[float, float](initial_amount, increase_amount)))
+    def set_list_minerals(self, list_mineral_to_keep):
+        """Set the list of solid phases at equilibrium in the system"""
+        self.thisptr.minerals_to_keep.reserve(len(list_mineral_to_keep))
+        for mine in list_mineral_to_keep:
+            self.thisptr.minerals_to_keep.push_back(mine)