Crystals without recipes

Crystallisation and crystal engineering is an area of considerable technological importance. Applications span numerous industries, including electronics, food, speciality chemicals, petroleum and pharmaceuticals. In each of these areas variations in crystal structure, crystallite size, morphology and crystal quality can have a significant effect on a product or process. The technological goal is to design and produce crystals with desired characteristics.

The current text is a relatively new title in the Oxford Chemistry Primers series, which aims to provide introductory material for topics covered in undergraduate courses in chemistry and chemical engineering. The texts are also excellent primers for postgraduate research students.

From Molecules to Crystallisers is a highly readable text that admirably achieves the objectives of the series. It addresses most of the essential ideas and concepts of crystallisation with a focus on principles and theoretical ideas. It is not a practical guide for preparing crystals and there are no recipes. The material is presented lucidly and in simple language. The mathematics employed is minimal with emphasis on the physical picture. The coverage in terms of chapters includes nucleation, crystal growth, morphology, polymorphism, number balances and size distributions, and characteristics of batch and continuous crystallisers.

A notable omission is crystallisation of macromolecules such as proteins. This is a highly significant area where the growth of good-quality crystals (required for the determination of molecular structure) is limiting our understanding of structure and function in molecular biology. Also, the text is biased towards molecular, mainly organic systems, with only a passing mention of inorganic materials.

There are some minor inaccuracies resulting, I expect, from an attempt to put the ideas across in the simplest manner. An example is the explanation of an order-disorder transition as a first-order transition where one of the phases has higher entropy. The more accepted definition is that such transitions are of a second-order nature where some order parameter changes continuously as a function of the selected thermodynamic variable.

From Molecules to Crystallisers is highly recommended for both undergraduates and research students attempting to get to grips with the principles underpinning crystallisation.

Jamshed Anwar is reader in computational pharmaceutical sciences, King's College, London.