diff --git a/src/MNH/ares.f b/src/MNH/ares.fx90
similarity index 98%
rename from src/MNH/ares.f
rename to src/MNH/ares.fx90
index 2a300286f4320976d6edfc3de07d6ab24a574337..88f5e5d29428bce1433119715c84ce0bc7ff8e58 100644
--- a/src/MNH/ares.f
+++ b/src/MNH/ares.fx90
@@ -1,4 +1,4 @@
-!MNH_LIC Copyright 1987-2019 CNRS, Meteo-France and Universite Paul Sabatier
+!MNH_LIC Copyright 1987-2021 CNRS, Meteo-France and Universite Paul Sabatier
 !MNH_LIC This is part of the Meso-NH software governed by the CeCILL-C licence
 !MNH_LIC version 1. See LICENSE, CeCILL-C_V1-en.txt and CeCILL-C_V1-fr.txt
 !MNH_LIC for details. version 1.
@@ -833,11 +833,8 @@ C....................................................................
 
 C...........PARAMETERS and their descriptions:
 
-      INTEGER      NCAT                 ! number of cations
-      PARAMETER  ( NCAT = 2 )
-
-      INTEGER      NAN                  ! number of anions
-      PARAMETER  ( NAN = 3 )
+      INTEGER, PARAMETER :: NCAT = 2 ! number of cations
+      INTEGER, PARAMETER :: NAN = 3  ! number of anions
 
 C...........ARGUMENTS and their descriptions
 
@@ -1374,16 +1371,32 @@ c     and the excess ammonium forms ammonum nitrate
        end if 
 c
        return
-       end
+       end subroutine awater
 
 c23456789012345678901234567890123456789012345678901234567890123456789012     
       
+      MODULE MODI_poly4
+      INTERFACE
+      function poly4(A,X)
+      real A(4), X
+      end function poly4
+      END INTERFACE
+      END MODULE MODI_poly4
+
       function poly4(A,X)
       real poly4
       real A(4), X     
        poly4 = A(1) + X * ( A(2) + X * ( A(3) + X * ( A(4) )))
-      return
-      end
+       return
+      end function poly4
+
+      MODULE MODI_poly6
+      INTERFACE
+      function poly6(A,X)
+      real A(6), X
+      end function poly6
+      END INTERFACE
+      END MODULE MODI_poly6
 
       function poly6(A,X)
       real poly6
@@ -1391,5 +1404,5 @@ c23456789012345678901234567890123456789012345678901234567890123456789012
       poly6 = A(1) + X * ( A(2) + X * ( A(3) + X * ( A(4) + 
      &           X * ( A(5) + X * (A(6)  )))))
        return
-      end      ! awater
+      end function poly6
 c //////////////////////////////////////////////////////////////////