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Crystal data are reported for molecular compounds of hexamethylenetetramine with phenol (1:1), resorcinol (1:1), hydroquinone (1:1), o‐cresol (1 : 1), m‐cresol (1:2), p‐chlorophenol (1:2), and p‐bromophenol (1:2).

Crystals of trans-2,5-di-p-bromobenzyl-2,5-diethoxycarbonylcyclohexane-l,4-dione are monoclinic, space group P21/c, with a= 14-41 (1), b = 6.024 (5), c= 14.79 (1) A, fl= 102-2 (1) ° and Z= 2. The structure was solved by direct methods and refined by full-matrix least-squares calculations with 1886 visual reflexions to a conventional R value of 0.129. The cyclohexane-l,4-dione moiety exists in the chair conformation, the more bulky p-bromobenzyl groups occupying the equatorial positions.

In the paper by Mak, Tse, Chong & Mok [Acta Cryst (1977), B33, 2980-29821 the seventh line of the Abstract should read: tetramine and hydroquinone molecules are tn and i...All the relevant information is contained in the Abstract. The aim of this little book, according to the author, 'is to give an account of those areas in chemistry where neutron techniques make well-established contributions and of the newer areas in which recent work promises very significant advances'. In this he succeeds very well. Chemists trained in diffraction methods will find the book thorough and easy to understand; those not acquainted with diffraction theory and methods will find the book more difficult to follow because of its concentrated nature. The book starts with a very brief introductory chapter containing a short history of diffraction methods and a general discussion of diffraction theory and the range of potential applications. This is followed by chapters describing the principles of neutron scattering and experimental methods. In a chapter on structural studies, the author gives a good account of typical analyses of single crystals by neutron diffraction to illustrate the scope of present methods, running from a study of sucrose and simple molecules like HC1, H2S, D 2, O 2, etc. through studies of heavy-element compounds, amino-acid derivatives and hydrogen bonds and molecular overcrowding. Book ReviewAfter a short discussion of direct methods of structure analysis and a chapter on correlation of X-ray and neutron data, the book contains a series of chapters describing modern applications of neutron scattering techniques: studies of biological materials, measurements of covalency, defects and non-stoichiometry, molecular spectroscopy, polymers and liquids, glasses and gases. Three appendices list the coherent scattering amplitudes of elements and isotopes for neutrons, elements and isotopes showing significant incoherent scattering and corresponding values of wavelength and energy for neutrons with equivalent values of optical wavenumber for energy transfer. There is a short bibliography and adequate index. Each chapter contains a list of references listing most of the classical studies and some very recent papers (up to 1976).Any chemist, or other scientist for that matter, interested in neutron scattering studies should read this book to get a basic understanding of the theory and a knowledge of the wide range of applications.

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