The growth and imperfection of the organic crystals are discussed in relation with the shapes and the binding forces. It is shown that the X-ray topography is the most suitable method for the observation of the lattice defects in the organic crystals compared with the optical or electron microscopic observations. The character of the dislocations are determined by the steric hindrances on the slip planes and also by the elastic energies of the dislocation lines. The X-ray topograpic observations of the crystals of long chain molecules, hexamethylbenzene, tetraoxane and three kinds of amino acids are shown. In these crystals, some of the dislocations with short Burgers vector are not observed. It is explained by the steric hindrances on the slip planes.
Developments of crystallization operation in chemical industries are summarized and recent studies in the United States, Europe and Japan are introduced. Especially, development of design theories of crystallizers is discussed in relation to crystallization phenomena of crystal growth and nucleation rate in a crystallizer. Average crystal growth rate used for calculating product crystal size and production rate in a crystallizer, is discussed in comparison with linear growth rate of a single crystal. These design theories have made crystallization processes popular in chemical industries. New crystallization processes have been developed for special purposes concerned with new separation methods under low consumption of energy, new processes for product characterized by high purity and special properties, new technology for prevention of water polution, and others. And also new type crystallizers have been studied for these processes. As these crystallization technology have been developed, new research themes have emerged. Behaviors of fines in a supersaturated solution are discussed based on the results newly obtained on nucleation and growth rate, considering chemical industrial operations, as an example.
A new model of heterogeneous nucleation from the vapour phase onto crystal surface is proposed. As a shape of the critical nucleus, the equilibrium form is assumed. On a crystal having orthorhombic prism shape, morphology of the critical nucleus and activation energy of formation of the nucleus on crystal surface, at macroscopic step and at macroscopic kink are discussed. The shape of the critical nucleus differs with these nucleation sites. The activation energy of formation of the nucleus decreases, in order of heterogeneous nucleation on surface, at macroscopic step and at macroscopic kink.