From 647485eab96ea795b0730275178227d8af4c8a8f Mon Sep 17 00:00:00 2001
From: rqthomas <rqthomas>
Date: Thu, 3 Oct 2019 11:51:50 -0400
Subject: [PATCH] added stop to carbon ph calculation if nnot converging

---
 src/aed2_carbon.F90 | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/aed2_carbon.F90 b/src/aed2_carbon.F90
index f03e263..4fb9e2b 100644
--- a/src/aed2_carbon.F90
+++ b/src/aed2_carbon.F90
@@ -1112,13 +1112,19 @@ SUBROUTINE Cal_pHfromTATC(TAx, TCx, pHx, K1F, K2F, TBF, KBF, KWF, KP1F, KP2F, KP
 
   REAL                 :: H, Denom, CAlk, BAlk, OH, PhosTop, PhosBot, PAlk, SiAlk, &
                         & FREEtoTOT, Hfree, HSO4, HF, Residual, Slope, deltapH, pHTol, ln10
+                        
+  INTEGER :: count
+  INTEGER :: max_count
 
   pHx      = 8.        !This is the first guess
   pHTol    = 0.0001    !tolerance for iterations end
   ln10     = log(10.)
   deltapH  = pHTol + 1
+  
+  count = 0
+  max_count = 100
 
-  DO WHILE (abs(deltapH) > pHTol)
+    DO WHILE (abs(deltapH) > pHTol .AND. count < max_count)
     H         = 10.**(-pHx)
     Denom     = (H*H + K1F*H + K1F*K2F)
     CAlk      = TCx*K1F*(H + 2.*K2F)/Denom
@@ -1143,6 +1149,7 @@ SUBROUTINE Cal_pHfromTATC(TAx, TCx, pHx, K1F, K2F, TBF, KBF, KWF, KP1F, KP2F, KP
 
     pHx       = pHx + deltapH  !% Is on the same scale as K1 and K2 were calculated...
 
+    count = count + 1
   END DO
 
   END SUBROUTINE Cal_pHfromTATC