From 41982f7e6350dcff9e5ca1294f298c70cb33752e Mon Sep 17 00:00:00 2001
From: Ian Bell <ian.h.bell@gmail.com>
Date: Thu, 15 Jan 2015 19:53:49 -0700
Subject: [PATCH] Phase envelope should only be able to build for pure fluids;
 closes #410

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
---
 src/Backends/Helmholtz/PhaseEnvelopeRoutines.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/Backends/Helmholtz/PhaseEnvelopeRoutines.cpp b/src/Backends/Helmholtz/PhaseEnvelopeRoutines.cpp
index 582d893a..ffe7948e 100644
--- a/src/Backends/Helmholtz/PhaseEnvelopeRoutines.cpp
+++ b/src/Backends/Helmholtz/PhaseEnvelopeRoutines.cpp
@@ -11,6 +11,7 @@ namespace CoolProp{
 
 void PhaseEnvelopeRoutines::build(HelmholtzEOSMixtureBackend &HEOS)
 {
+    if (HEOS.get_mole_fractions_ref().size() < 2){throw ValueError("Cannot build phase envelope for pure fluid");}
     std::size_t failure_count = 0;
     // Set some imput options
     SaturationSolvers::mixture_VLE_IO io;