The crystal structure of anhydrous sodium chromate

Miller, John Jaimerson
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Almost all solid substances are crystalline, and in most cases it is possible to obtain single crystals that are large enough to make physical measurements upon. The structure of crystals is, then, of great importance in the study of the structure of matter. Although they were limited to the measurement of the interfacial angles that appeared on the crystals, early experimental crystallographers obtained a vast amount of valuable crystallographic data. As early as 1908 P. Groth published several large volumes of such data. This was before Laue's discovery of x-ray diffraction by crystals. These data have been very helpful to the modern x-ray crystallographer. The early crystallographers were able to classify all crystals into six systems which they further divided into thirty-two classes. The mathematical crystallographers, working with the problem of possible arrangements of points in space, have shown that there are fourteen distinct space lattices upon which point groups may be arranged in a continuous manner. By applying every possible element of symmetry that each point group could possess when placed upon the various lattices, the mathematical crystallographers have shown that there are two hundred thirty different space groups possible. It remained for the x-ray crystallographers to identify these points as atoms and to determine their positions in the unit cells. After Laue's discovery in 1912 great progress began in the experimental determination of the structure of crystals. Under the leadership of such investigators as the Braggs in England, DeBroglie in France, Debye, Scherer, Schiebold and Ewald in Germany, and Wyckoff, Hull, Pauling and Zachariasen in this country a vast amount of information has been gathered in this field. It is the desire of the writer that the crystallographic data obtained during this investigation may prove to be of value in future crystallographic or chemical research