From 32fa56108dbfc2208b1e12840cfda5cd6fae0f86 Mon Sep 17 00:00:00 2001
From: Ian Bell <ian.h.bell@gmail.com>
Date: Mon, 8 Dec 2014 18:22:01 -0500
Subject: [PATCH] Implemented rhomass_critical function in AbstractState. 
 Closes https://github.com/CoolProp/CoolProp/issues/303

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
---
 include/AbstractState.h | 24 +++++++++++++++++++-----
 src/AbstractState.cpp   |  6 ++++--
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/include/AbstractState.h b/include/AbstractState.h
index 9164bc34..a635af6c 100644
--- a/include/AbstractState.h
+++ b/include/AbstractState.h
@@ -347,12 +347,19 @@ protected:
     For mixtures, it is the exact critical point pressure calculated by the methods of Michelsen( \todo fill in reference)
     */
     double p_critical(void);
-    /// Return the critical molar density in mol/m^3
-    /**
-    For pure fluids, this is the critical point molar density
-    For mixtures, it is the exact critical point molar density calculated by the methods of Michelsen( \todo fill in reference)
-    */
+    /// 
+    /** \brief Return the critical molar density in mol/m^3
+	 * 
+	 * For pure fluids, this is the critical point molar density
+     * For mixtures, it is the exact critical point molar density calculated by the methods of Michelsen( \todo fill in reference)
+     */
     double rhomolar_critical(void);
+	/** \brief Return the critical molar density in kg/m^3
+	 * 
+	 * For pure fluids, this is the critical point molar density
+     * For mixtures, it is the exact critical point molar density calculated by the methods of Michelsen( \todo fill in reference)
+     */
+    double rhomass_critical(void);
     
     /// Return the triple point pressure 
     double p_triple(void);
@@ -494,6 +501,13 @@ protected:
 	 * Matthis Thorade, Ali Saadat, "Partial derivatives of thermodynamic state properties for dynamic simulation", 
 	 * Environmental Earth Sciences, December 2013, Volume 70, Issue 8, pp 3497-3503
 	 * 
+	 * Like with \ref first_saturation_deriv, we can express the derivative as
+	 * \f[ \left(\frac{\partial y}{\partial T}\right)_{\sigma} = \left(\frac{\partial y}{\partial T}\right)+\left(\frac{\partial y}{\partial p}\right)\left(\frac{\partial p}{\partial T}\right)_{\sigma} \f]
+	 *
+	 * where \f$ y \f$ is already a saturation derivative. So you might end up with something like 
+	 * 
+	 * \f[ \left(\frac{\partial \left(\frac{\partial T}{\partial p}\right)_{\sigma}}{\partial T}\right)_{\sigma} = \left(\frac{\partial \left(\frac{\partial T}{\partial p}\right)_{\sigma}}{\partial T}\right)+\left(\frac{\partial \left(\frac{\partial T}{\partial p}\right)_{\sigma}}{\partial p}\right)\left(\frac{\partial p}{\partial T}\right)_{\sigma} \f]
+	 * 
 	 * @param Of1 The parameter that the derivative is taken of
 	 * @param Wrt1 The parameter that the derivative is taken with respect to
 	 * */
diff --git a/src/AbstractState.cpp b/src/AbstractState.cpp
index 01b4ae24..40876ddb 100644
--- a/src/AbstractState.cpp
+++ b/src/AbstractState.cpp
@@ -188,7 +188,7 @@ double AbstractState::trivial_keyed_output(int key)
     case irhomolar_critical:
         return this->rhomolar_critical();
     case irhomass_critical:
-        return this->rhomolar_critical()*molar_mass();
+        return this->rhomass_critical();
     case iODP:
         return this->calc_ODP();
     case iGWP100:
@@ -322,7 +322,9 @@ double AbstractState::p_triple(void){
 double AbstractState::rhomolar_critical(void){
     return calc_rhomolar_critical();
 }
-
+double AbstractState::rhomass_critical(void){
+    return calc_rhomolar_critical()*molar_mass();
+}
 double AbstractState::hmolar(void){
     if (!_hmolar) _hmolar = calc_hmolar();
     return _hmolar;