Ho Chak Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 122-126). / Acknowledgment --- p.i / Table of contents --- p.ii / List of figures --- p.iv / List of tables --- p.v / Abstract --- p.ix / Chapter Part I --- Determination of sulphide / General introduction --- p.1 / Spectrophotometric determination of sulphide --- p.5 / Chapter 1. --- Introduction --- p.5 / Chapter A. --- Review of the reported methods for the determination of sulphide --- p.5 / Chapter B. --- General description of the proposed method --- p.13 / Chapter 2. --- Experimental section --- p.18 / Chapter A. --- Preservation of samples --- p.18 / Chapter B. --- Sample pre-treatment --- p.19 / Chapter C. --- Separation/preconcentration of sulphide --- p.19 / Chapter D. --- Spectrophotometric determination of sulphide by proposed method --- p.24 / Chapter E. --- Spectrophotometric determination of sulphide by standard methylene blue method as the counter-check method --- p.32 / Chapter 3. --- Results and discussions --- p.34 / Chapter A. --- Optimization of the proposed spectrophotometric method --- p.34 / Chapter B. --- Optimization of the separation/preconcentration methods --- p.45 / Chapter C. --- Construction of the calibration graph for the spectrophotometric determination of sulphide and determination of the molar absorptivity coefficient --- p.53 / Chapter D. --- Precision and detection limit of the proposed spectrophotometric method --- p.54 / Chapter E. --- Interferences studies of the proposed method --- p.56 / Chapter F. --- Spectrophotometric determination of sulphide in water --- p.60 / Chapter G. --- Spectrophotometric determination of sulphide in beers --- p.63 / Chapter H. --- Spectrophotometric determination of sulphide in orange juices --- p.66 / Chapter 4. --- Conclusions --- p.68 / References --- p.70 / Chapter Part II --- Determination of fluoride / General introduction --- p.75 / Spectrophotometric determination of fluoride --- p.78 / Chapter 1. --- Introduction --- p.78 / Chapter A. --- Review of the reported methods for the determination of fluoride --- p.78 / Chapter B. --- General description of the proposed scheme for the spectrophotometric determination of fluoride in animal feeds --- p.84 / Chapter 2. --- Experimental Section --- p.87 / Chapter A. --- Ashing of the animal feed samples --- p.87 / Chapter B. --- Reduction of interferences in the ashed sample solutions using anion exchange resin --- p.89 / Chapter C. --- Preparation of solutions for the calibration graph and the ashed sample solutions for the spectrophotometric measurement --- p.90 / Chapter D. --- Spectrophotometric determination of fluoride in the ashed samples --- p.92 / Chapter E. --- Potentiometric determination of fluoride in the ashed sample solutions by the FISE method as the counter-check method --- p.93 / Chapter 3. --- Results and discussions --- p.94 / Chapter A. --- Ashing conditions of the animal feed samples --- p.94 / Chapter B. --- Removal of the interferences in the ashed sample solutions --- p.99 / Chapter C. --- Construction of the calibration graph for the spectrophotometric determination of fluoride --- p.112 / Chapter D. --- Precision of the spectrophotometric method --- p.113 / Chapter E. --- Spectrophotometric determination of fluoride in animal feeds --- p.114 / Chapter F. --- Potentiometric determination of fluoride in animal feeds by the FISE method as the counter-check method --- p.117 / Chapter 4. --- Conclusions --- p.120 / References --- p.122

Copies of author's previously published articles in pocket. Bibliography: leaves 203-219. Main objectives of the thesis are: i. to verify a sealed chamber acid digestion technique for dissolution of plant material for total F analysis by a F ion selective electrode.--ii. to improve this technique for routine, rapid F analysis of plant material.--iii. to identify the inorganic ionic species of F which could be present in the soil solution.--iv. to determine which of these species are taken up by the plant root and those which are toxic to the plant.

Copies of author's previously published articles in pocket. / Bibliography: leaves 203-219. / xv, 219 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Main objectives of the thesis are: i. to verify a sealed chamber acid digestion technique for dissolution of plant material for total F analysis by a F ion selective electrode.--ii. to improve this technique for routine, rapid F analysis of plant material.--iii. to identify the inorganic ionic species of F which could be present in the soil solution.--iv. to determine which of these species are taken up by the plant root and those which are toxic to the plant. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1996

This thesis reports exploratory studies on the synthesis of new vanadium and copper-containing compounds, with a particular emphasis on preparing new magnetically-active materials with S = ½ spin configurations. Eighteen crystal structures are reported, sixteen of which represent new compounds. These materials were studied for magnetic behaviour where appropriate. The sixteen vanadium-containing compounds were prepared using either the hydrothermal, Solvothermal or ionothermal synthesis methods at temperatures ranging from 60 °C to 200 °C. Inorganic cations and organic moieties were used as templating agents to direct the structures, often targeting potentially frustrated lattices based on triangular motifs by using ‘triangular' templating molecules such as guanidine. Solvent choices, as well as reactant ratios were all varied in order to produce the new oxide, fluoride and oxyfluoride compounds of vanadium. Three families of vanadium compounds were prepared from these methods; a family of 1D vanadium (IV) oxyfluoride ladder compounds of general formula AVOF₃ (A=K⁺, Rb⁺, Cs⁺ or NH₄⁺), and a family of 1D vanadium fluoride chain compounds of general formula A₂VF₅ (A=K⁺ or NH₄⁺). The third family is comprised of three vanadium-containing compounds of varying dimensionality that share guanidine as the common organic moiety. Several miscellaneous compounds of vanadium such as clusters and a new V (IV) layer were synthesized, and are reported. The two copper compounds containing compounds, analogous to the pseudo-kagome compound, Cu₃Bi(SeO₃)₂O₂Br, were prepared via solid-state techniques. A detailed neutron diffraction study was carried out on the two compounds to measure the evolution of the magnetic properties from room temperature down to 2.5 K. Representational analysis was utilised in order to provide a detailed magnetic model of the compounds.

Fluoride ion is an accompanying impurity in a wide variety of chemical gypsum throughout the world. In this study, the Ion Selective Electrode (ISE) method, the Ion Chromatography (IC) method and the standard Willard and Winter method of fluoride analysis were adapted and compared for use in the quantification of fluoride in South African chemical gypsum. During the use of ISE, the pH of sample solutions was found to be a critical parameter for the results to be meaningful. An operating pH of approximately 5 was suitable for consistency of results. It was important to ensure the existence of the ionised form of fluorine in solution, because the detection was based on the sensitivity of the membrane electrode to this species. In the case of the Willard and Winter method, the traditional visual indicator titration was replaced by a more sensitive spectrophotometric detection, because of low fluoride levels in the chemical gypsum. The parameter sensitive reaction rate approach was adapted, and the reaction allowed to go to completion to enable measurement with a bench top spectrophotometer. The IC method required a good separator since fluoride ions usually eluted too early for detection on common ion exchange columns. The data handling of the chromatographic software was thoroughly examined and consistent integration of the chromatograms maintained. Sample preparation of the chemical gypsum involved particle size reduction through grinding. No trend between fluoride impurity and the particle size of the sample was observed. <p. The quantity of fluoride in Kynoch and Omnia phosphogypsum were found to be 0.10% and 0.04% respectively. The Tioxide chemical gypsum, titangypsum, was found to contain in the region of 0.02% fluoride. Generally, the level of fluorine (F) has to be reduced to about 0.2% before phosphogypsum can be used as substitute for natural gypsum in the cement industry. The aim of this study is to critically evaluate three analytical methods, namely, the Willard and Winter standard method of fluoride analysis, the ISE method, and IC as applied in the quantification of fluoride in chemical gypsum. Secondly, the efficiency of treatment of the chemical gypsum with water, lime and sulphuric acid was investigated. The ISE method was found to be faster and relatively simpler versus both Willard and Winter and the IC methods. The IC method was quite superior for indicating general complexity of the sample and it was faster than the Willard and Winter method. The standard Willard and Winter method was generally found to be long and tedious. The three methods validated one another as percentages of fluoride in the chemical gypsum samples were the same. The study indicated that a sulphuric acid pretreatment of the chemical gypsum was the most effective (90%) in the removal of fluoride impurity compared to the lime treatment and water washing (9%). However, the water washing would be inexpensive for practical treatment of chemical gypsum at plant level. / Thesis (PhD(Chemistry))--University of Pretoria, 2006. / Chemistry / unrestricted

There has been an increase in the interest in fluoride materials over the last decade. This interest has focused on multiferroic materials and kagome lattices, to name but a few areas. This thesis focuses on the synthesis and crystallographic characterisation of selected transition metal fluorides and oxyfluorides. Work is presented on the tetragonal tungsten bronze solid solutions of KₓFeF₃, where x = 0.58 and x ≈ 0.5, and the copper analogue, K₃Cu₃Fe₂F₁₅; the kagome structure of Cs₂ZrCu₃F₁₂; and hydrothermal reactions using vanadium, manganese, or molybdenum as the transition metals in the formation of new fluorides and oxyfluorides. The tetragonal tungsten bronze compounds KₓFeF₃ (x = 0.58 and x ≈ 0.5) are both tetragonal at 500 K. In the variant with the lower K-content, there is a clear phase separation into two tetragonal phases even at this temperature. The K₀.₅₈FeF₃ sample separates into two distinct phases below 340 K to possess one tetragonal and one orthorhombic phase. Then at roughly 300 K, both samples undergo a phase transition where the tetragonal phase in the P4/mbm space group in K₀.₅₈FeF₃ changes to an orthorhombic phase with a larger unit cell; and the tetragonal phase in P4₂bc for the K₀.₅FeF₃ sample changes to the same orthorhombic model, whilst the P4/mbm model remains unchanged. The evolution of the lattice parameters and phase fractions is studied in detail using synchrotron powder X-ray diffraction (sPXRD). The kagome structure investigated, Cs₂ZrCu₃F₁₂, possesses the “ideal” kagome lattice at room temperature, but previous work has suggested that there is a phase transition at 225 K. The two structures are determined by single crystal X-ray diffraction at 300 K and 125 K. Variable temperature sPXRD studies are performed between these two temperature ranges to determine the phase evolution as a function of temperature. The structure changes from a rhombohedral to a monoclinic phase at low temperature. This is the result of the buckling of the kagome layers at the phase transition. The Zr⁴⁺ ion changes from 6 to 7 coordinate and this is seen as the main driving force for the distortion of the kagome layer from its “ideal” planar arrangement. ii The phase transition is first-order as seen from the electrical impedance measurements. The hydrothermal reactions presented reveal seven new materials and their crystal structures. Sr₂V₂F₁₀·H₂O is new and found to be isostructural to Sr₂Fe₂F₁₀·H₂O. BaVO₂F₃ is a cubic material that is potentially piezoelectric. Two hybrid organic inorganic manganese compounds are reported. The ladder structure (C₃N₂H₅)[Mn₂F₆(H₂O)₂] crystallises in a polar space group and shows promise as a candidate for multiferroic studies. The second hybrid material, (C₇NH₁₆)₂[MnF₅(H₂O)]·2H₂O, crystallises in a centrosymmetric space group. The Mo hybrid materials are all centrosymmetric and possess isolated molybdenum-centred monomeric or dimeric octahedral units.