In the course of the past few years, X-ray and spectroscopic methods of analysis have found an increasing usefulness at the Dow Chemical Company. There are a large number of different types of problems on which information can be obtained by the variations of apparatus and technic which are possible in these two fields. It is not the purpose of this paper, however, to discuss these methods or applications in general, but to describe in some detail a scheme of classifying and using X-ray diffraction patterns which has been found very helpful in one particular application of X-rays — namely, that of identifying unknown substances by means of their Hull powder diffraction patterns.

The inherent power of X-ray diffraction as a practical means of chemical analysis was pointed out a good many years ago. Having a different theoretical basis and depending upon an entirely different technic than other methods, it would be expected to supplement the information to be obtained from other methods and, at times, to be applicable where other methods are not suitable. It appears, however, that the use of this method has not increased at a rate commensurate with its unique and valuable features, and that it is used by relatively few academic and industrial laboratories.

The reflection shift δ2Θ caused by a radial shift δr of the sample away from its tangential position at the focusing circle is examined for grazing incidence diffraction and grazing excidence diffraction. Experimental results for residual strain/stress evaluation on thin films using a Bragg–Brentano diffractometer with a grazing incidence equipment are presented. Grazing excidence diffraction is less sensitive to δr than grazing incidence diffraction.

The trihydrated ammonium trioxalato-ferrate (III) (NH4)3(Fe(C2O4)3)·3H2O cristallizes in the monoclinic system with:

The space group is P21/c[14].

The binary phase diagram of para-dibromobenzene and para-chloroiodobenzene is characterized by a partial miscibility with a peritectic invariant. Unit cell parameters have been determined and their variation analyzed as a function of composition.

Bragg–Brentano X-ray powder diffractometry data and refined unit cell parameters are reported for a synthetic sample of dolerophanite, copper (II) oxysulphate [Cu2O(SO4)], prepared by heating AR copper (II) sulphate anhydrate in a muffle furnace at 725 °C. The data are compared with (i) two Debye–Scherrer patterns published by Mrose [Am. Mineral. 6, 146–153 (1961)]—for a synthetic sample and for a natural dolerophanite, the latter being pattern 13–189 in the ICDD Powder Diffraction File and (ii) a Debye–Scherrer pattern for a synthetic dolerophanite described by Borchardt and Daniels [J. Phys. Chem. 61, 917–921 (1957)]. A calculated pattern is also presented for the crystal structure of dolerophanite described by Effenberger [Monatschefte fur Chemie. 116, 927–931 (1985)]. The measured and calculated patterns reported here show reasonable internal consistency for both line positions and intensity data. While the agreement between these results and the data sets of Mrose is sound in terms of line positions, there is substantial disagreement overall between the intensity values given by the authors and those of Mrose. There is closer agreement between the intensities from the current study and those of Borchardt and Daniels.

The Powder Diffraction File of crystallographic data has been converted from printed data cards to a computer database. Extensive testing, review, and editing of the database were completed, the history and first stages of which are presented. Computer programs used to create and analyze the database are described.

The unit cell dimensions of minerals in the smectite group, regular and random mixed-layer groups, and halloysite shown in the Mineral Powder Diffraction File (1986) have been refined by least-squares analysis in the hexagonal system with a primitive lattice with indices restricted to hk or 00l reflections. Trioctahedral minerals have larger a unit-cell dimensions than dioctahedral minerals.

The crystal structure of α-CoSO4 has been refined by the Rietveld method from X-ray powder diffraction data. The structure is orthorhombic, space group Pnma, a = 8.6127(4), b = 6.7058(3), c = 4.7399(2) Å, V = 273.75(3) Å3. Final RB = 2.41%, RP = 5.24%, RWP=6.66%, RWP (expected) =5.74% (WP =weighted profile). The structure consists of edge-sharing octahedral chains parallel to [010] interconnected by SO4 tetrahedra.

X-ray powder diffraction data are reported for the [(NH4)3Al1−xFex/2Crx/2(C2O4)3]·3H2O solid solution. The crystal system is triclinic with space group P1. Refined unit-cell parameters are given for the compositions x=0.10, 0.50 and 0.80.

Crystal data and results of structure refinements for MnSi are reported. The material is cubic, P213, with a = 4.5603(2) Å, Vd = 94.84(1) Å3, Z = 4, Dx = 5.815 Mg/m3. Intensity data were obtained from a Stoe transmission type diffractometer equipped with a position sensitive detector. CuKα1 radiation, λ = 1.5405981 Å was employed. Germanium was used as an internal standard for the determination of the lattice constant (aGe= 5.6582 Å). The structure was refined by the Rietveld method by aid of three different programs.

The heterocycle of a functionalized 2-imidazoline, C15N2OH18, was obtained by reaction when 2-bromo, 2-alkenoïc ketone was allowed to react with a monosubstituted benzamidine. The compound presents a R*R* configuration. X-ray powder diffraction data have been obtained from single multifaceted brown crystals prepared at 273 K in benzene with triethylamine as catalyst. Chemical analysis gives a purity better than 99%. This compound crystallizes in the monoclinic space group P21/c [14]. The cell parameters were determined by employing single-crystal diffraction methods (Bragg and precession patterns) and were refined from accurate powder diffractometer data recorded at T = 293 (1) K.