diff --git a/Phreeqc.cpp b/Phreeqc.cpp
index 90aa8c59..0d7863b4 100644
--- a/Phreeqc.cpp
+++ b/Phreeqc.cpp
@@ -1092,7 +1092,6 @@ void Phreeqc::init(void)
 	OPRESS					= -100.;
 	A0                      = 0;
 	aphi                    = NULL;
-	spec                    = NULL;
 	cations                 = NULL;
 	anions                  = NULL;
 	neutrals                = NULL;
@@ -1137,9 +1136,6 @@ void Phreeqc::init(void)
 	sit_MAXCATIONS          = 0;
 	sit_FIRSTANION          = 0;
 	sit_MAXNEUTRAL          = 0;
-	sit_IPRSNT              = NULL;
-	sit_M                   = NULL;
-	sit_LGAMMA              = NULL;
 	/* tidy.cpp ------------------------------- */
 	a0                      = 0;
 	a1                      = 0;
diff --git a/Phreeqc.h b/Phreeqc.h
index f96ad816..177d64e4 100644
--- a/Phreeqc.h
+++ b/Phreeqc.h
@@ -1802,7 +1802,8 @@ protected:
 	LDBLE OTEMP, OPRESS;
 	LDBLE A0;
 	struct pitz_param* aphi;
-	struct species **spec, **cations, **anions, **neutrals;
+	std::vector<struct species*> spec;
+	struct species ** cations, ** anions, ** neutrals; // pointers to spec
 	int count_cations, count_anions, count_neutrals;
 	int MAXCATIONS, FIRSTANION, MAXNEUTRAL;
 	struct pitz_param *mcb0, *mcb1, *mcc0;
@@ -1836,8 +1837,8 @@ protected:
 	LDBLE sit_A0;
 	int sit_count_cations, sit_count_anions, sit_count_neutrals;
 	int sit_MAXCATIONS, sit_FIRSTANION, sit_MAXNEUTRAL;
-	int *sit_IPRSNT;
-	LDBLE *sit_M, *sit_LGAMMA;
+	std::vector<int> sit_IPRSNT;
+	std::vector<double> sit_M, sit_LGAMMA;
 	std::vector<int> s_list, cation_list, neutral_list, anion_list, ion_list, param_list;
 
 	/* tidy.cpp ------------------------------- */
diff --git a/pitzer.cpp b/pitzer.cpp
index 6e1a1a33..4da1eafd 100644
--- a/pitzer.cpp
+++ b/pitzer.cpp
@@ -56,15 +56,9 @@ pitzer_tidy(void)
 	/*
 	 *  allocate pointers to species structures
 	 */
-	if (spec != NULL)
-		spec = (struct species **) free_check_null(spec);
-	spec = (struct species **)
-		PHRQ_malloc((size_t) (3 * s.size() * sizeof(struct species *)));
-	if (spec == NULL)
-		malloc_error();
-	for (i = 0; i < 3 * (int)s.size(); i++)
-		spec[i] = NULL;
-	cations = spec;
+	spec.clear();
+	spec.resize(3 * s.size(), NULL);
+	cations = &spec[0];
 	neutrals = &(spec[s.size()]);
 	anions = &(spec[2 * s.size()]);
 	MAXCATIONS = (int)s.size();
@@ -1649,7 +1643,7 @@ pitzer_clean_up(void)
 	theta_params.clear();
 	LGAMMA.clear();
 	IPRSNT.clear();
-	spec = (struct species **) free_check_null(spec);
+	spec.clear();
 	aphi = (struct pitz_param *) free_check_null(aphi);
 	M.clear();
 
diff --git a/prep.cpp b/prep.cpp
index 0bfb091e..eda023b0 100644
--- a/prep.cpp
+++ b/prep.cpp
@@ -5814,9 +5814,8 @@ save_model(void)
 		}
 		/* charge */
 		last_model.count_surface_charge = (int) use.Get_surface_ptr()->Get_surface_charges().size();
-		last_model.surface_charge =
-			(const char **) PHRQ_malloc( use.Get_surface_ptr()->Get_surface_charges().size() *
-								  sizeof(char *));
+		last_model.surface_charge =(const char **) PHRQ_malloc( use.Get_surface_ptr()->Get_surface_charges().size() *
+				sizeof(char *));
 		if (last_model.surface_charge == NULL)
 			malloc_error();
 		for (i = 0; i < (int) use.Get_surface_ptr()->Get_surface_charges().size(); i++)
diff --git a/sit.cpp b/sit.cpp
index a92a8313..74455f0e 100644
--- a/sit.cpp
+++ b/sit.cpp
@@ -35,12 +35,10 @@ sit_tidy(void)
 	/*
 	 *  allocate pointers to species structures
 	 */
-	if (spec != NULL) spec = (struct species **) free_check_null(spec);
-	spec = (struct species **) PHRQ_malloc((size_t) (3 * s.size() * sizeof(struct species *)));
-	if (spec == NULL) malloc_error();
-	for (i = 0; i < 3 * (int)s.size(); i++) spec[i] = NULL;
+	spec.clear();
+	spec.resize(3 * s.size(), NULL);
 
-	cations = spec;
+	cations = &spec[0];
 	neutrals = &(spec[s.size()]);
 	anions = &(spec[2 * s.size()]);
 	sit_MAXCATIONS = (int)s.size();
@@ -53,16 +51,9 @@ sit_tidy(void)
 	/*
 	 *  allocate other arrays for SIT
 	 */
-	if (sit_IPRSNT != NULL) sit_IPRSNT = (int *) free_check_null(sit_IPRSNT);
-	sit_IPRSNT = (int *) PHRQ_malloc((size_t) (3 * s.size() * sizeof(int)));
-	if (sit_IPRSNT == NULL) malloc_error();
-	if (sit_M != NULL) sit_M = (LDBLE *) free_check_null(sit_M);
-	sit_M = (LDBLE *) PHRQ_malloc((size_t) (3 * s.size() * sizeof(LDBLE)));
-	if (sit_M == NULL) malloc_error();
-	if (sit_LGAMMA != NULL) sit_LGAMMA = (LDBLE *) free_check_null(sit_LGAMMA);
-	sit_LGAMMA = (LDBLE *) PHRQ_malloc((size_t) (3 * s.size() * sizeof(LDBLE)));
-	if (sit_LGAMMA == NULL) malloc_error();
-
+	sit_IPRSNT.resize(3 * s.size());
+	sit_M.resize(3 * s.size());
+	sit_LGAMMA.resize(3 * s.size());
 
 	for (i = 0; i < (int)s.size(); i++)
 	{
@@ -509,11 +500,11 @@ sit_clean_up(void)
 	}
 	sit_params.clear();
 	sit_param_map.clear();
-	sit_LGAMMA = (LDBLE *) free_check_null(sit_LGAMMA);
-	sit_IPRSNT = (int *) free_check_null(sit_IPRSNT);
-	spec = (struct species **) free_check_null(spec);
+	sit_LGAMMA.clear();
+	sit_IPRSNT.clear();
+	spec.clear();
 	aphi = (struct pitz_param *) free_check_null(aphi);
-	sit_M = (LDBLE *) free_check_null(sit_M);
+	sit_M.clear(); 
 
 	return OK;
 }
@@ -805,7 +796,7 @@ int Phreeqc::
 jacobian_sit(void)
 /* ---------------------------------------------------------------------- */
 {
-	LDBLE *base;
+	std::vector<double> base;
 	LDBLE d, d1, d2;
 	int i, j;
 Restart:
@@ -817,16 +808,7 @@ Restart:
 		sit();
 		residuals();
 	}
-	base = (LDBLE *) PHRQ_malloc((size_t) count_unknowns * sizeof(LDBLE));
-	if (base == NULL)
-	{
-		malloc_error();
-		return OK;
-	}
-	for (i = 0; i < count_unknowns; i++)
-	{
-		base[i] = residual[i];
-	}
+	base = residual; // std::vectors
 	d = 0.0001;
 	d1 = d * LOG_10;
 	d2 = 0;
@@ -900,7 +882,6 @@ Restart:
 		molalities(TRUE);
 		if (max_unknowns > pz_max_unknowns) 
 		{
-			base = (LDBLE *) free_check_null(base);
 			gammas_sit();
 			jacobian_sums();
 			goto Restart;
@@ -960,7 +941,6 @@ Restart:
 		sit();
 	mb_sums();
 	residuals();
-	free_check_null(base);
 	return OK;
 }