Phase equilibria and their applications

Abstract

This special issue on phase behavior was instigated by the successful JEEP (Journées d'Étude desÉquilibres entre Phases) meeting in March 2016 in Paris. The meeting is held yearly for over forty years and was established by a group of French researchers back in the seventies working on phase equilibria. It explains why its name is French even if the working language during the conference is nowadays English, as a large community from different countries participates (which has led to the proposition to call the conference 'Joint European days on Equilibria between Phases'). This special issue is not the proceedings of the conference, but it does demonstrate the vast research area in which phase equilibria are of importance.Phase behavior can appear as something magical. To take a simple example, the freezing or melting of water occurs at constant temperature, which means that mixtures of water and ice can be used to control temperature very accurately. In first instance, and possibly even after one understands thermodynamics, this can appear a miracle.An interesting question related to phase behavior is for example the preferential formation of one form of calcium carbonate by shellfish, whereas a more stable form of calcium carbonate exists. How could this happen? How does the animal control the formation of a less stable form? How can the animal prevent the interconversion into the more stable form? Similar questions exist in the pharmaceutical realm, where formulators need to ascertain the stability of a drug formulation, consisting for example of a powder, a tablet, or a suspension. A patient expects that his or her drug will work even after it has been stored on a shelf in the bathroom for over a year. This requires understanding of the solid-state behavior of drugs and mixtures of drugs and their sensitivity to water. Therefore, the FDA (Food and Drug Administration) and EMA (European Medicine Agency) require the pharmaceutical industry to prove that they can maintain their formulation for a given period of time.Similar questions exist for metal tools in industry used under high pressure, strain, and high temperatures. Machinery cannot fail when working under demanding circumstances, as it can cause dangerous situations and it will result in loss of material and profit. Another interesting issue is the taste and mouth feel of chocolate, which highly depends on the proper crystal form of the cocoa butter. It possesses several different crystal structures, and the most sought after form melts just above 30• C in a