diff --git a/ext/tpx/CarbonDioxide.cpp b/ext/tpx/CarbonDioxide.cpp
index 5e717b53b..24774a51f 100755
--- a/ext/tpx/CarbonDioxide.cpp
+++ b/ext/tpx/CarbonDioxide.cpp
@@ -11,6 +11,8 @@
 #include <math.h>
 #include <string.h>
 
+using namespace std;
+
 namespace tpx {
 
 /* 
@@ -312,7 +314,7 @@ double CarbonDioxide::Psat(){
 
     double log, sum=0,P;
     if ((T < Tmn) || (T > Tc)) {
-        cout << " error in Psat " << TempError << endl;
+        std::cout << " error in Psat " << TempError << endl;
         set_Err(TempError); // Error("CarbonDioxide::Psat",TempError,T);
     }
     for (int i=1;i<=8;i++)
diff --git a/ext/tpx/Sub.cpp b/ext/tpx/Sub.cpp
index e1c91d172..7b9d66179 100755
--- a/ext/tpx/Sub.cpp
+++ b/ext/tpx/Sub.cpp
@@ -7,6 +7,8 @@
 #include <fstream>
 #include <stdio.h>
 
+using namespace std;
+
 namespace tpx {
 
     static string fp2str(double x, string fmt="%g") {
diff --git a/ext/tpx/Sub.h b/ext/tpx/Sub.h
index e15106209..3f3767bbf 100755
--- a/ext/tpx/Sub.h
+++ b/ext/tpx/Sub.h
@@ -21,19 +21,18 @@
 
 #include <iostream>
 #include <string>
-using namespace std;
 
 namespace tpx {
 
     class TPX_Error {
     public:
-        TPX_Error(string p, string e) {
+        TPX_Error(std::string p, std::string e) {
             ErrorMessage = e;
             ErrorProcedure = p;
         }
         virtual ~TPX_Error(){}
-        static string ErrorMessage;
-        static string ErrorProcedure;
+        static std::string ErrorMessage;
+        static std::string ErrorProcedure;
     };
 
 
@@ -70,7 +69,7 @@ namespace tpx {
 
     const double Undef = 999.1234;
 
-    string errorMsg(int flag);
+    std::string errorMsg(int flag);
 
     class Substance { 
     public:
@@ -202,8 +201,8 @@ namespace tpx {
 	int Err;
         double m_energy_offset;
         double m_entropy_offset;
-        string m_name;
-        string m_formula;
+        std::string m_name;
+        std::string m_formula;
 
         //	virtual double Xm(int k) { return 1.0;}
         //virtual int Species() { return 1;}
diff --git a/ext/tpx/utils.cpp b/ext/tpx/utils.cpp
index be81b09ac..c050af3f0 100755
--- a/ext/tpx/utils.cpp
+++ b/ext/tpx/utils.cpp
@@ -1,6 +1,8 @@
 #include "subs.h"
 #include "utils.h"
 
+using namespace std;
+
 namespace tpx {
 
     static string lowercase(string s) {