Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 136-143).

A study of the Lauth's Violet absorptiometry method for the analysis of sodium sulphide was carried out. The order of adding the reactants in the development of the color, the use of three different methods of titration for standardizing the solutions used for determining the calibration factor, and the effects of varying the concentrations of the reagents were all investigated. In the formation of Lauth's Violet from sodium sulphide, addition of reactants in the order base electrolyte, sodium sulphide, and p-phenylenediamine was shown to be best. The arsenious oxide method of titration was selected for determining the concentration of sodium sulphide in standard solutions used for calibration. If the reagents: base electrolyte containing ferric chloride, and p-phenylenediamine, were used at the concentrations of 0.16% and 5% by weight, respectively, the calibration factor remained constant up to concentrations 16 grams per litre of sodium sulphide. The applicability of the Lambert-Beer law and the effect of sodium thiosulphate on the absorptiometry method also were studied in detail. The oxidation of sodium sulphide was studied under atmospheric pressure at various temperatures by use of two different apparatuses. From the measurements of the amounts of oxygen absorbed, the oxidation of sodium sulphide probably gives disulphide, thiosulphate, sulphite and sulphate. The stoichiometry corresponds to thiosulphate being the main product of this reaction. The rate of absorption of oxygen with simultaneous, oxidation of sodium sulphide was observed to decrease, with increasing temperature from 25° to 45°C Nevertheless, the maximum absorption rate was found at 55°C, and the absorption rate decreases again with temperature at least to 85°C. The reaction orders for the oxidation of sodium sulphide depend upon temperature, being second order at 25°C, order of 1.5 at 35° and 45°C., and first order from 55° to 85°C. The reaction order with respect to oxygen is first order, irrespective of temperature. The maximum rate of oxidation also occurs at 55°C. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Thesis (Ph.D.)--McMaster University, 2004. / Advisor: James Dowling. Includes bibliographical references.

[Truncated abstract] Areal bone mineral density (BMD) is measured routinely in the clinic by a quantitative radiological technique, dual-energy X-ray absorptiometry (DXA). BMD is used widely to assess non-invasively but indirectly the mechanical fragility of bone and consequently is able to predict fracture risk. While BMD correlates well with in vitro measurements of bone strength it does not directly measure a mechanical property; half of incident minimally traumatic fractures in women occur with BMD values above the World Health Organisation defined threshold for osteoporosis. This arises partly because the mechanical strength of bone is dependent on its structural geometry and material strength as well as bone mineral mass. Essentially, bones fracture when load stresses exceed the mechanical capacity of the material to withstand them. The structural geometry (i.e., the amount of bone tissue and its complex three-dimensional arrangement within the macroscopic bone envelope) defines the stresses produced by a given load, while the intrinsic load capacity of the material is defined by the composition and microstructure of the bone tissue itself. Hip structural analysis (HSA) is a technique that elucidates the structural geometric component of bone strength; essentially combining information available from conventional DXA images of the proximal femur with a biomechanical beam model based on the stresses arising in a combination of pure bending and axial compression. A version of HSA has recently been released commercially, and has obtained US Food and Drug Administration approval for its clinical application. ... Given the acknowledged limitations of the HSA method when applied to 2-D projection images, a 3-D approach to structural geometry, using imaging modalities such as pQCT and QCT or a recently introduced version of DXA that mimics QCT, is indicated for the future. With that in mind and the possibility of the anthropometric phantom being adopted for future accuracy and precision assessments, improvements in the design of this phantom are recommended. Studies to better understand and verify Contents v the relevance of the 'local buckling' phenomenon as a structural geometric factor in the genesis of macro-fractures are also recommended. In summary, it is essential that superior (compared to BMD) non-invasively determined clinical predictors of bone fragility leading to fracture be investigated. Structural geometric variables are potential candidates. This has led to consideration of; (i) the need to progress beyond BMD for a more sensitive and specific bone strength measurement; (ii) theoretical advantages of structural geometry over BMD; (iii) limitations of the current HSA technique based on DXA, including those introduced by its restrictive assumptions; (iv) the value of HSA in longitudinal studies, exemplified by the 'normal' but rapid skeletal changes seen in human lactation, with possible implications for an analogous study of the menopause; and (v) an investigation, using a custom-designed anthropometric phantom, of the adaptation of HSA to certain emerging imaging modalities and methods able to resolve bone structural geometry in three dimensions.