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Various strategies have been tested for obtaining integrated intensities from x-ray powder diffractometer data. An asymmetric pseudo-Voigt profile function was used to fit the pattern in the region above 2θ = 35̊ (Cu-Kα radiation). At lower angles where the asymmetry was strongest and the profile function not suitable the peaks were integrated numerically. A smooth background function was estimated from the regions of minimum intensity of the pattern. The profile parameters were initially refined in small ranges of about 10̊ 2θ in order to determine their 2θ-dependence. Thereafter final refinements of peak intensities were undertaken using the profile parameters thus determined. Analysis of data from the mineral Fe-akermanite, Ca₂Mg₀. ₄Fe₀. δSi₂O₇, generated 173 integrated intensities with 1 > 2δ(1) out of 187 positions separated in 2θ by more than 0,02̊. Of the total of 213 reflections in the range, those overlapping exactly or separated by < 0,02̊ were treated as single peaks. The structure was refined using an overall isotropic temperature parameter and a parameter to compensate for preferred orientation, giving an unweighted residual of 10,4% for 14 parameters. / Thesis (M.Sc.)-University of Durban-Westville, 1988.

The base metal and platinum group metal extractive processes for two South African refineries were examined using x-ray powder diffraction. Base metal refinery matte contained nickel sulphide (Ni3S2), copper sulphide (Cu2S), nickel-copper alloy (Ni-Cu), iron oxide (Fe3O4) - nickel iron oxide (NiFe2O4) and nickel oxide (NiO). Nickel iron oxide and cobalt sulphide (CO3S4) were found in matte aeration cavities. Matte fast cooling caused alloy zoning. Alloy stoichiometry and weight percentages of matte constituents were calculated. Magnetic separation of the alloy phase was unfeasible due to high bulk and poor separation from Ni3S2. Sulphuric acid matte leaching produced residues containing copper sulphide (Cul.8S) and nickel sulphides (Ni3S4, NiS). Potassium cyanide residue leaching produced NiS-rich residues, while thiourea / hydrochloric acid leaching produced residues almost free of copper sulphide. PGM concentrates were examined. Base metals occurred as: copper sulphate pentahydrate; copper sulphate hydroxide hydrate (CU4SO4(OH)6'H2O); copper sulphide (CuS); copper platinum (Cu3Pt); nickel oxide (NiO); nickel iron oxide (NiFe2O4). Lead occurred as lead sulphate and silicon as quartz and enstatite ((Mg,Fe,Al)SiO3). Heating the concentrate to 260°C with sulphuric acid converted copper sulphide to copper sulphate. PGMs were mostly metallic. Overdrying concentrates caused pgm sintering. Drying with sulphuric acid reduced sintering. PGM oxidative leach solubility was examined. Platinum sulphide (Pt,Pd)S caused low platinum and palladium solubility. (Ru,Rh,Ir,Pt)AsS caused low rhodium and ruthenium solubility. Platinum-rhodium (Rh0.57Pt0.43), ruthenium-osmium (~Ru16Os), iridosmine (Os,Ir,Ru) also caused low pgm solubility. Silver chloride remained in residues. Concentrate overdrying produced insoluble sintered platinum, palladium monoxide, and ruthenium dioxide. In minor concentrates sintered platinum, rhodium selenide (RhSe2+x), ruthenium dioxide and possibly palladium monoxide lowered pgm solubility. Precipitates and salts were examined. Iron precipitated as iron oxide hydroxide (B-FeOOH); gold as metallic gold; lead as lead chloride. Common salts were: sodium chloride; sodium iron hydroxide sulphate hydrate (Na2Fe(SO4)2(OH)'3H2O); ammonium chloride; sodium carbonate monohydrate. PGM-Iead fusion was examined. Fusion produced the insoluble alloy Pb(Pd,Pt)3. Ruthenium dioxide reacted with lead carbonate forming lead ruthenium oxide (Pb2Ru2O6.5). Nitric acid insoluble residues also contained lead sulphate and iron oxide (Fe3O4). This study demonstrated that solution problems can be understood by identifying the crystalline insoluble phases in intractable residues. / Thesis (Ph.D.)-University of Natal, Durban, 1994.

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This thesis consists of the structures of two compounds as determined by single crystal x-ray diffraction. The first structure is that of a phosphazene - iodine complex: hexamethylcyclotriphosphazene - iodine (1:1 adduct) and the second structure is the redetermination of sodium formate. Crystals of hexamethylcyclotriphosphazene - iodine (1:1 adduct) are triclinic, a = 10.707(13), b = 8.873 (5), c = 8.871(6)Å, α = 96. 65 (6), β = 103.91 (12), ɤ = 97.81(12)°, Z = 2, space-group PI. The structure was determined with Mo-K« diffractometer data by Patterson and Fourier synthesis, and was refined by full-matrix least-squares calculations to R = 0.053 for 1934 observed reflexions. The iodine molecule is weakly bonded to a nitrogen atom on the phosphazene ring, N - I = 2.417(7), I - I = 2. 823 (1) Å, N - I - I = 177.8(2)°. The six-membered phosphazene ring is slightly, but significantly, ncn-planar, the conformation being that of a chair. The molecule has pseudo-m symmetry. Two distinct P-N bonds are present; the longer ones, mean P - N = 1.64 Å, involve the nitrogen that is weakly bonded to the iodine molecule, while the other four P-N bonds are equivalent, mean P - N = 1.598 Å. All the P - C bonds are equivalent, mean P - C = 1.789 Å. The mean endocyclic N - P - N and P - N - P angles are 114.7 and 124.0° respectively, while the mean exocyclic C - P - C angle is 104°. Crystals of sodium formate are mcnoclinic, a = 6.2590 (6), b = 6.7573 (16) , c = 6.716 (5) Å, β = 116.140(6)°, Z = 4, space-grcup C2/c. The structure was determined by direct methods, and was refined by electron density and full-matrix least-squares procedures to E = 0.022 for 250 reflexions. Sodium formate is planar and has C2V symmetry. Partial charges were refined on the formate ion. The partial charges found on each atom are as follows: 0 -0.23(1)e, C +0.16(3)e, H -0.49(10)e, and Sa +0.79(14)e. The sodium ion has six oxygen neighbours at an average distance of 2.45 Å and there are weak Na. ..0 interactions. There is a C - H...Na hydrogen bond which forms continuous rows of sodium formate ions. The C - 0 bond distance is 1.246(1)Å and the 0 - C - 0 angle is 126.3(2)°. / Science, Faculty of / Chemistry, Department of / Graduate