diff --git a/interfaces/python/ctml_writer.py b/interfaces/python/ctml_writer.py
index 1ad63d341..a1e011312 100644
--- a/interfaces/python/ctml_writer.py
+++ b/interfaces/python/ctml_writer.py
@@ -904,7 +904,7 @@ class gas_transport(transport):
     """
     def __init__(self, geom = 'nonlin',
                  diam = 0.0, well_depth = 0.0, dipole = 0.0,
-                 polar = 0.0, rot_relax = 0.0):
+                 polar = 0.0, rot_relax = 0.0, omega_ac = 0.0):
         """
         :param geom:
             A string specifying the molecular geometry. One of ``atom``,
@@ -920,6 +920,9 @@ class gas_transport(transport):
         :param rot_relax:
             The rotational relaxation collision number at 298 K. Dimensionless.
             Default: 0.0
+        :param w_ac:
+            Pitzer's acentric factor.  Dimensionless.
+            Default: 0.0
         """
         self._geom = geom
         self._diam = diam
@@ -927,6 +930,7 @@ class gas_transport(transport):
         self._dipole = dipole
         self._polar = polar
         self._rot_relax = rot_relax
+        self._w_ac = omega_ac
 
     def build(self, t):
         #t = s.addChild("transport")
@@ -939,6 +943,7 @@ class gas_transport(transport):
         addFloat(t, "dipoleMoment", (self._dipole, 'Debye'),'%8.3f')
         addFloat(t, "polarizability", (self._polar, 'A3'),'%8.3f')
         addFloat(t, "rotRelax", self._rot_relax,'%8.3f')
+        addFloat(t, "omega_ac", self._w_ac, '%8.3f')
 
 class rate_expression(object):
     pass
@@ -2189,20 +2194,20 @@ class RedlichKwongMFTP(phase):
                  elements = '',
                  species = '',
                  note = '',
+                 reactions = 'none',
+                 kinetics = 'GasKinetics',
                  initial_state = None,
                  activity_coefficients = None,
                  transport = 'None',
                  options = []):
 
-        phase.__init__(self,name, 3, elements, species, note, 'none',
+        phase.__init__(self,name, 3, elements, species, note, reactions,
                        initial_state,options)
         self._pure = 0
+        self._kin = kinetics
         self._tr = transport
         self._activityCoefficients = activity_coefficients
 
-    def conc_dim(self):
-        return (0,0)
-
     def build(self, p):
         ph = phase.build(self,p)
         e = ph.child("thermo")
@@ -2219,8 +2224,9 @@ class RedlichKwongMFTP(phase):
         if self._tr:
             t = ph.addChild('transport')
             t['model'] = self._tr
-        k = ph.addChild("kinetics")
-        k['model'] = 'none'
+        if self._kin:
+            k = ph.addChild("kinetics")
+            k['model'] = self._kin
 
 
 class redlich_kwong(phase):