The structure and powder diffraction data of Hägg-carbide (χ-Fe5C2) have been redetermined and improved by X-ray diffraction. Experimental values of 2θ, corrected for systematic errors, relative peak intensities, lattice spacings, and the Miller indices of 27 observed reflections up to 100° 2θ are reported. The unit cell is monoclinic (space group C2/c, Z=4) with a=11.588 Å, b=4.579 Å, c=5.059 Å, and β=97.75°. The crystal structure has been refined by Rietveld analysis, resulting in Rwp=0.073.

(Na0.6H0.4)(Ta0.7Nb0.3)O3 was synthesized by heating a tantalum/niobium scale containing two sodium tantalate/niobate phases :Na14(Ta0.7Nb0.3)12O37·31H2O and NaH2Ta0.7Nb0.3O4. Powder X-ray diffraction data for (Na0.6H0.4)(Ta0.7Nb0.3)O3 indicated it to be a cubic perovskite (ABO3/ReO3 type structure) with unit cell a0=3.894 Å. The compound is analogous to the mineral lueshite (NaNbO3), and to the high temperature forms of NaTaO3 and NaNbO3. Powder diffraction data for (Na0.6H0.4)(Ta0.7Nb0.3)O3 will be useful in the analysis of synthetic tantalum/niobium concentrates.

X-ray powder diffraction data for chioroquine sulphate monohydrate [7—chloro—4—(4—diethylamino—1—methylbutylamino)—quinoline sulphate monohydrate, C18H26C1N3· H2SO4 · H2O] have been determined. Crystals of chioroquine sulphate monohydrate are orthorhombic, space group P212121 with a=9.0134(7), b=11.7417(6), c= 19.850(1) Å, Z=4, and Dx= 1.378 g cm−3. The F30 index is 121 (0.0062, 40).

All known occurrences of nickelphosphide (Ni,Fe)3P—a mineral encountered mainly in meteoritic irons—represent relatively small grains, which prevents acquiring powder data of a reasonable quality. Synthetic analogues of this mineral, corresponding chemically to that found in the meteorite Vicenice, have been synthesized. Powder data collected using a standard laboratory diffractometer in the Bragg–Brentano geometry are presented. The space group of nickelphosphide is identical to that of schreibersite (Fe,Ni,Co)3P and synthetic Ni3P—I4. The unit-cell dimensions refined from the powder data are a=9.0168(1) Å, c=4.4501(1) Å, and V=361.80(1) Å3, with Z=8.

Two compounds have been studied by means of powder diffraction and their unit cell parameters are reported. The monoclinic cell parameters for dimethylgermanyl-bridged bis cyclopentadienyl tetracarbonyl diruthenium are a=11.03(2) Å, b=13.65(2) Å, c=11.609(2) Å, β=105.81(1)°, Z=4, space group P21/n (No. 14), Dx=2.135 mg/m3. The monoclinic cell parameters for λ-dimethylsilyl-dicyclopentadienyl-π, π′-tetracarbonyl diruthenium, are a=11.113(3) Å, b=13.60(1) Å, c=11.674(7) Å, and β=106.00(3)°, Z=4, space group P21/n (No. 14), and Dx=1.946 mg/m3. The cells found for the two compounds are in good agreement with those obtained from single crystal X-ray diffractometry.

A novel synthesis method of fibrillar trimolybdates with the use of Ag2Mo3O10∙2H2O as a precursor has been used successfully to synthesize methylammonium trimolybdate, (CH3NH3)2Mo3O10∙H2O. The crystal structure of this compound was determined by X-ray powder diffraction method and refined by the Rietveld method. The compound is orthorhombic, space group Pnma (62), with a=11.241(3), b=7.585(1), and c=15.516(4) Å. The redetermined crystal structure of the precursor and the structure of the title compound are compared and discussed.