Abstract
SIB WILLIAM BBAGG, delivering the Sir Henry Trueman Wood lecture before the Royal Society of Arts on December 16, gave an account of the development of crystal analysis by X-rays during the last decade. The X-ray data may now be made to give a ‘shadow picture’ of the molecular structure which can be compared with chemical ideas of structural grouping. The dimensions of the structure can be determined with very considerable accuracy-the separation of atoms within about one per cent-and it is found that the characteristic separation of, say, carbon atoms persists in a number of related structures. Chemical ideas of valency, double and triple linkages, the benzene ring are all clarified by this method of study of the atomic separations. The investigation of structures is progressive in the sense that the information already gained can be used in the attack on more complicated structures. Important results have been obtained with proteins, and the properties of the protein chain explain the peculiarities of hair, muscle and similar biological structures. The X-ray diffraction patterns obtained from alloys show how a small quantity of an alloying element fits into the main lattice; while the progressive addition of alloy leads to the formation of new, characteristic lattices. The peculiar alloy structure called the yphase depends apparently on a fixed proportion (13:21) of atoms to valency electrons. X-rays, aided by electron diffraction, also give information about the crystal texture-the size and arrangement of the crystals as distinct from their inner structure; and the texture is the key to such different problems as the working of metals and the function of biological structures.
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Development of Crystal Analysis. Nature 139, 104–105 (1937). https://doi.org/10.1038/139104c0
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DOI: https://doi.org/10.1038/139104c0