Phase Equilibria and Crystallization Techniques

This chapter begins by looking at the use of the information available in phase diagrams to define the nature of the crystalline phase that will appear under a given set of conditions of temperature, pressure, and composition. The phase rule tells us under which conditions certain systems can be in equilibrium. The chapter then examines the nature of the driving force for crystallization processes and outlines some typical techniques used for preparing crystalline materials, including suspension crystallization and the solidification of melts. Crystallization is a kinetic process and, traditionally, chemists are familiar with the use of reagent concentration to describe the driving force for the chemical rate process. However, in the case of crystallization, the concentration range over which the process can occur is limited by the equilibrium composition of the system corresponding to the conditions chosen.