Powder photographs identifications with

To aid in identification of the low-temperature modification, the ten strongest lines in order of decreasing intensity have d spacings 2.95, 2.77, 2.02, 1.63, 1.596, 1.252,1.384, 1.216,1.308 A. Again these data are from a powder photograph taken with CuXa radiation. 

Chapter V, on identification by X-ray methods, is concerned with the practical details of taking X-ray powder photographs, and also includes elementary diffraction theory, taken as far as is necessary for most identification problems. 

If the spacings of the arcs on a powder photograph do not lead to identification, the determination of unit cell dimensions from the powder photograph may be attempted the methods are described in Chapter VI. If crystals large enough to be handled individually can be picked out of the specimen, single-crystal rotation photographs may be taken and used for identification this also is dealt with in Chapter VI. 

Applications of knowledge of unit cell dimensions. 1. Identification. The use of powder photographs for identification has been described in Chapter V the simplest method is to calculate the spacings of the crystal planes from the positions of the reflections, and to use these spacings together with the relative intensities as determinants, If this information does not lead to identification, it may be worth while to attempt to discover the unit cell dimensions, since for many substances unit cell dimensions have been determined and published, but the details of the X-ray diffraction photographsliave not been recorded. 

The X-ray powder diffraction pattern of parbendazole has been measured using a Philips PW-1050 diffractometer, equipped with a single-channel analyzer and using copper Ka radiation. The pattern obtained is shown in Fig. 5.1, and the data of scattering angle (° 26) and the relative intensities (f/7max) are presented in Table 5.1 (as photographic and diffractometric pattern data) as an attempt to establish a reference chart for the purpose of identification of parbendazole. 

Crystalline materials can be identified by rapid computerized powder diffraction techniques. The principle of this technique [6,7] is that the crystallites within a sample, placed in a collimated x-ray beam, reflect x-rays at specific angles and intensities. The diffraction pattern can be recorded photographically, using a camera, e.g. a Debye-Scherrer camera, or using a powder diffractometer. Chemical analysis depends on the fact that each chemical composition and crystallographic structure produces a unique angular distribution of diffracted intensity. Analysis is based on comparison of the diffractometer scan with known standards. Typical applications of the powder diffraction technique to polymers would be the identification of mineral fillers in engineering resins, the nature of crystalline contaminants and determination of crystalline phases in a material. 

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