diff --git a/phreeqcpp/integrate.cpp b/phreeqcpp/integrate.cpp
index f2123696..200909d2 100644
--- a/phreeqcpp/integrate.cpp
+++ b/phreeqcpp/integrate.cpp
@@ -1115,7 +1115,7 @@ calc_psi_avg(cxxSurfaceCharge *charge_ptr, LDBLE surf_chrg_eq, LDBLE nDbl, LDBLE
 		{
 			if (!surf_ptr->Donnan_factors.empty())
 			{
-				std::copy(std::begin(surf_ptr->Donnan_factors), std::end(surf_ptr->Donnan_factors), cgc);
+				std::copy(surf_ptr->Donnan_factors.begin(), surf_ptr->Donnan_factors.end(), cgc);
 				z1 = cgc[0];
 				z2 = cgc[1];
 				z_1 = cgc[2];
diff --git a/phreeqcpp/transport.cpp b/phreeqcpp/transport.cpp
index d6b0535c..109fd662 100644
--- a/phreeqcpp/transport.cpp
+++ b/phreeqcpp/transport.cpp
@@ -6089,8 +6089,8 @@ viscosity(cxxSurface *surf_ptr)
 				s_charge_p = surf_ptr->Get_surface_charges()[i1];
 				l_water = s_charge_p.Get_mass_water();
 				z_g_map.insert(s_charge_p.Get_z_gMCD_map().begin(), s_charge_p.Get_z_gMCD_map().end());
-				for (auto& x : z_g_map)
-					x.second *= ratio_surf_aq;
+				for (std::map<double, double>::iterator x = z_g_map.begin(); x != z_g_map.end(); ++x)
+					x->second *= ratio_surf_aq;
 			}
 			else
 			{
@@ -6099,11 +6099,11 @@ viscosity(cxxSurface *surf_ptr)
 				for (i = 1; i < i1_last - 1; i++)
 				{
 					s_charge_p = surf_ptr->Get_surface_charges()[i];
-					for (auto& x : z_g_map)
-						x.second += s_charge_p.Get_z_gMCD_map()[x.first];
+					for (std::map<double, double>::iterator x = z_g_map.begin(); x != z_g_map.end(); ++x)
+						x->second += s_charge_p.Get_z_gMCD_map()[x->first];
 				}
-				for (auto& x : z_g_map)
-					x.second *= ratio_surf_aq;
+				for (std::map<double, double>::iterator x = z_g_map.begin(); x != z_g_map.end(); ++x)
+					x->second *= ratio_surf_aq;
 				l_water = mass_water_surfaces_x;
 			}
 			l_mu_x = eq_plus = eq_min = 0;