diff --git a/doc/RELEASE.TXT b/doc/RELEASE.TXT
index 90c99ad9..fe1208dc 100644
--- a/doc/RELEASE.TXT
+++ b/doc/RELEASE.TXT
@@ -3,8 +3,8 @@ Version @PHREEQC_VER@: @PHREEQC_DATE@
   	-----------------
 	October 8, 2024
   	-----------------
-	PHREEQC: Improved algorithem for transport of heat in TRANSPORT, and included
-	additional viscosity effects in transport calculations.
+	PHREEQC: Revised the multicomponent diffusion calculation of heat and solutes, 
+	accounting now for the heat also for the T-dependent viscosity of the solutions.
 	
 	-----------------
 	October 8, 2024
@@ -17,7 +17,10 @@ Version @PHREEQC_VER@: @PHREEQC_DATE@
 	October 8, 2024
   	-----------------
 	PHREEQC: Fixed  bug in MIX that produced erroneous temperature and pressure
-	if the solutions being mixed did not have 1 kg of water.
+	if the solutions being mixed did not have 1 kg of water. (Note that PHREEQC does 
+	not consider the heat content of the solutions when the temperature of the mixture 
+	is calculated.)
+	
 
 Version 3.8.2: August 29, 2024
   	-----------------
diff --git a/mytest/ex13_impl.out b/mytest/ex13_impl.out
index 0dbc383c..d672ac17 100644
--- a/mytest/ex13_impl.out
+++ b/mytest/ex13_impl.out
@@ -1,4 +1,3 @@
-WARNING: Database file from DATABASE keyword is used; command line argument ignored.
    Input file: ex13_impl
   Output file: ex13_impl.out
 Database file: ../database/wateq4f.dat
@@ -262,6 +261,10 @@ Calculating transport: 10 (mobile) cells, 1 shifts, 338 mixruns...
 
 WARNING: No porosities were read; used the value 3.00e-01 from -multi_D.
 WARNING: 
-Calculating implicit transport: 10 (mobile) cells, 1 shifts, 15 mixruns, max. mixf = 10.
+Calculating implicit transport: 10 (mobile) cells, 1 shifts, 16 mixruns, max. mixf = 10.
 
 
+-------------------------------
+End of Run after 1.322 Seconds.
+-------------------------------
+
diff --git a/src/transport.cpp b/src/transport.cpp
index 28b1790e..7bde99d4 100644
--- a/src/transport.cpp
+++ b/src/transport.cpp
@@ -52,6 +52,7 @@ struct MOLES_ADDED /* total moles added to balance negative conc's */
 } *moles_added;
 int count_moles_added;
 
+#if !defined(NPP)
 #if defined(_MSC_VER) && (_MSC_VER <= 1400) // VS2005
 #  define nullptr NULL
 #endif
@@ -61,7 +62,7 @@ int count_moles_added;
 #    define nullptr NULL
 #  endif
 #endif
-
+#endif
 #if defined(PHREEQCI_GUI)
 #ifdef _DEBUG
 #define new DEBUG_NEW
@@ -1842,7 +1843,7 @@ fill_spec(int l_cell_no, int ref_cell)
 	class master *master_ptr;
 	LDBLE dum, dum2, l_tk_x;
 	LDBLE lm;
-	LDBLE por, por_il, viscos_f0, viscos_f, viscos_il_f0, viscos, viscos_0;
+	LDBLE por, por_il, viscos_f0, viscos_f, viscos_il_f0, viscos, viscos0;
 	bool x_max_done = false;
 	std::set <std::string> loc_spec_names;
 
@@ -1914,13 +1915,15 @@ fill_spec(int l_cell_no, int ref_cell)
 	* correct diffusion coefficient for temperature Dw(TK) = Dw(298.15) * exp(dw_t / TK - dw_t / 298.15), SC data from Robinson and Stokes, 1959
 	*   and viscosity, D_T = D_298 * viscos_0_298 / viscos_0_tk
 	*/
-	sol_D[l_cell_no].viscos_0 = viscos_0 = Utilities::Rxn_find(Rxn_solution_map, l_cell_no)->Get_viscos_0();
 	sol_D[l_cell_no].viscos   = viscos   = Utilities::Rxn_find(Rxn_solution_map, l_cell_no)->Get_viscosity();
+	sol_D[l_cell_no].viscos_0 = viscos0 = Utilities::Rxn_find(Rxn_solution_map, l_cell_no)->Get_viscos_0();
+	if (!sol_D[l_cell_no].viscos_0)
+		sol_D[l_cell_no].viscos_0 = viscos0 = viscos;
 	/*
 	* put temperature factor in por_factor which corrects for porous medium...
 	*/
-	dum = viscos_0_25 / viscos_0;
-	dum2 = viscos_0 / viscos;
+	dum = viscos_0_25 / viscos0;
+	dum2 = viscos0 / viscos;
 	viscos_f0 *= dum;
 	viscos_il_f0 *= dum;
 	viscos_f *= dum2;
@@ -2129,7 +2132,7 @@ fill_spec(int l_cell_no, int ref_cell)
 			if (s_ptr->dw_a_v_dif)
 			{
 				sol_D[l_cell_no].spec[count_spec].dw_a_v_dif = s_ptr->dw_a_v_dif;
-				sol_D[l_cell_no].spec[count_spec].Dwt *= pow(viscos_0 / viscos, s_ptr->dw_a_v_dif);
+				sol_D[l_cell_no].spec[count_spec].Dwt *= pow(viscos0 / viscos, s_ptr->dw_a_v_dif);
 			}
 			else
 				sol_D[l_cell_no].spec[count_spec].dw_a_v_dif = 0.0;