diff --git a/phreeqcpp/Phreeqc.h b/phreeqcpp/Phreeqc.h
index 75b9267e..02f4ccc9 100644
--- a/phreeqcpp/Phreeqc.h
+++ b/phreeqcpp/Phreeqc.h
@@ -1400,6 +1400,7 @@ protected:
 	*---------------------------------------------------------------------- */
 	std::vector<class unknown*> x;
 	size_t count_unknowns;
+	size_t sit_aqueous_unknowns;
 	size_t max_unknowns;
 
 	class unknown* ah2o_unknown;
diff --git a/phreeqcpp/mainsubs.cpp b/phreeqcpp/mainsubs.cpp
index 2ebd8fd3..75d0a889 100644
--- a/phreeqcpp/mainsubs.cpp
+++ b/phreeqcpp/mainsubs.cpp
@@ -73,6 +73,11 @@ initialize(void)
 	change_surf[0].next = TRUE;
 	change_surf[1].cell_no = -99;
 	change_surf[1].next = FALSE;
+	/*
+	* define constant named log_k
+	*/
+	class logk* logk_ptr = logk_store("XconstantX", TRUE);
+	read_log_k_only("1.0", &logk_ptr->log_k[0]);
 
 #ifdef PHREEQCI_GUI
 	g_spread_sheet.heading            = NULL;
diff --git a/phreeqcpp/prep.cpp b/phreeqcpp/prep.cpp
index f9d995ed..59df4ba1 100644
--- a/phreeqcpp/prep.cpp
+++ b/phreeqcpp/prep.cpp
@@ -1240,8 +1240,7 @@ build_model(void)
 	}
 	if (dl_type_x != cxxSurface::NO_DL && (/*pitzer_model == TRUE || */sit_model == TRUE)) //DL_pitz
 	{
-		error_msg("-diffuse_layer option not available for Pizer or SIT model",
-				  STOP);
+		warning_msg("-diffuse_layer option not tested for SIT model");
 	}
 /*
  *   Sum diffuse layer water into hydrogen and oxygen mass balances
@@ -1285,6 +1284,7 @@ build_model(void)
 			k++;
 			count_unknowns++;
 		}
+		sit_aqueous_unknowns = count_unknowns - j0;
 	}
 	/*
  *   Rewrite phases to current master species
diff --git a/phreeqcpp/sit.cpp b/phreeqcpp/sit.cpp
index 6268e450..27825c26 100644
--- a/phreeqcpp/sit.cpp
+++ b/phreeqcpp/sit.cpp
@@ -1117,7 +1117,8 @@ model_sit(void)
 			{
 				
 				count_basis_change++;
-				count_unknowns -= (int)this->s_x.size();
+				//count_unknowns -= (int)this->s_x.size();
+				count_unknowns -= sit_aqueous_unknowns;
 				reprep();
 				full_pitzer = false;
 			}
diff --git a/phreeqcpp/spread.cpp b/phreeqcpp/spread.cpp
index 03cf4439..967c1c9f 100644
--- a/phreeqcpp/spread.cpp
+++ b/phreeqcpp/spread.cpp
@@ -1136,7 +1136,7 @@ copy_token_tab(std::string& token, const char **cptr)
  *      EOL,
  *      UNKNOWN.
  */
-	int i, j, return_value;
+	int i, return_value;
 	char c;
 /*
  *   Strip leading spaces
diff --git a/phreeqcpp/tidy.cpp b/phreeqcpp/tidy.cpp
index 18c5adca..4c95089b 100644
--- a/phreeqcpp/tidy.cpp
+++ b/phreeqcpp/tidy.cpp
@@ -1824,7 +1824,9 @@ tidy_punch(void)
 		for (size_t i = 0; i < current_selected_output->Get_totals().size(); i++)
 		{
 			std::pair< std::string, void *> &pair_ptr = current_selected_output->Get_totals()[i];
-			pair_ptr.second = master_bsearch(pair_ptr.first.c_str());
+			std::string noplus = pair_ptr.first;
+			replace(noplus, "+", "");
+			pair_ptr.second = master_bsearch(noplus.c_str());
 		}
 
 		/* molalities */
@@ -3800,6 +3802,21 @@ tidy_min_surface(void)
 			*/
 			for (int jj = 0; jj < count_elts; jj++)
 			{
+				if (elt_list[jj].elt->primary == NULL)
+				{
+					error_string = sformatf("Primary master species missing for %s",
+						elt_list[jj].elt->name);
+					error_msg(error_string, CONTINUE);
+					break;
+				}
+				if (elt_list[jj].elt->primary->s == NULL)
+				{
+					error_string = sformatf(
+						"Species missing for %s", elt_list[jj].elt->name);
+					error_msg(error_string, CONTINUE);
+					break;
+				}
+					
 				if (elt_list[jj].elt->primary->s->type != SURF
 					&& elt_list[jj].coef < 0
 					//&& elt_list[jj].elt->primary->s != s_hplus