diff --git a/Phreeqc.h b/Phreeqc.h
index 072834822..01a49e457 100644
--- a/Phreeqc.h
+++ b/Phreeqc.h
@@ -6,6 +6,7 @@
 #      define WINVER 0x0400
 #    endif
 #    include <afx.h>
+// #    define nullptr NULL
 #  endif
 #  include <windows.h>
 #  if defined(PHREEQCI_GUI)
@@ -2095,12 +2096,22 @@ char* _string_duplicate(const char* token, const char* szFileName, int nLine);
 // https://stackoverflow.com/questions/2915672/snprintf-and-visual-studio-2010
 
 #if defined(_MSC_VER) && (_MSC_VER < 1900)
-
+#if (_MSC_VER == 1400) // VS2005
+namespace std {
+	__inline bool isnan(double num) {
+		return _isnan(num) != 0;
+	}
+}
+#endif
 #include <stdarg.h>
 
 #define snprintf c99_snprintf
 #define vsnprintf c99_vsnprintf
 
+#pragma warning( push )
+// warning C4793: 'vararg' : causes native code generation
+#pragma warning( disable : 4793 )
+
 __inline int c99_vsnprintf(char *outBuf, size_t size, const char *format, va_list ap)
 {
     int count = -1;
@@ -2124,6 +2135,7 @@ __inline int c99_snprintf(char *outBuf, size_t size, const char *format, ...)
 
     return count;
 }
+#pragma warning( pop )
 #endif // defined(_MSC_VER) && (_MSC_VER < 1900)
 
 #endif //_INC_MISSING_SNPRINTF_H
diff --git a/common/Utils.cxx b/common/Utils.cxx
index 1eafd4399..0e8d461ae 100644
--- a/common/Utils.cxx
+++ b/common/Utils.cxx
@@ -12,6 +12,10 @@
 #include "float.h"
 #include <cmath>
 
+#if defined(_MSC_VER) && (_MSC_VER <= 1400) // VS2005
+#  define nullptr NULL
+#endif
+
 #if defined(PHREEQCI_GUI)
 #ifdef _DEBUG
 #define new DEBUG_NEW
diff --git a/global_structures.h b/global_structures.h
index 98f16eefd..020770f77 100644
--- a/global_structures.h
+++ b/global_structures.h
@@ -6,9 +6,14 @@
  *   #define DEFINITIONS
  * ---------------------------------------------------------------------- */
 #if !defined(NAN)
-#define NAN nan("1")
+#  if defined(_MSC_VER) && (_MSC_VER <= 1400) // VS2005
+#    include <limits>
+#    define NAN std::numeric_limits<double>::signaling_NaN()
+#  else
+#    define NAN nan("1")
+#  endif
 #endif
-#define MISSING -9999.999            
+#define MISSING -9999.999
 #include "NA.h"   /* NA = not available */
 
 #define F_C_MOL 96493.5			/* C/mol or joule/volt-eq */
diff --git a/integrate.cpp b/integrate.cpp
index 03e1c3049..8f20cd277 100644
--- a/integrate.cpp
+++ b/integrate.cpp
@@ -1074,7 +1074,7 @@ calc_psi_avg(cxxSurfaceCharge *charge_ptr, LDBLE surf_chrg_eq, LDBLE nDbl, std::
 		cgc[10] = { 0.36, 0.1721, 0.798, 0.287, 0.1457, 1.2, 0.285, 0.372 };
 
 	if (!surf_p->Donnan_factors.empty())
-		std::copy(std::begin(surf_p->Donnan_factors), std::end(surf_p->Donnan_factors), cgc);
+		std::copy(surf_p->Donnan_factors.begin(), surf_p->Donnan_factors.end(), cgc);
 
 	cgc[1] *= pow(nDbl, cgc[2]) * pow(Gamma, cgc[3]) * pow(mu_x, cgc[4]);