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The work in this thesis consists of three related studies. (i) Further investigations have been made into the mechanism of the photochemical reaction between (Mn[sub]2(CO)[sub]8{PBu[sub]3}[sub]2) and benzyl halides, equation 1. A previous study in these laboratories, which included an (Mn[sub]2(CO)[sub]8{PBu[sub]3}[sub]2) + PhCH[sub]2Cl -->(MnCl(CO)[sub]4PBu[sub]3) + (Mn(PhCH[sub]2)(CO)[sub]4PBu[sub]3) 1 examination of reaction kinetics, led to the suggestion that the mechanism involved CO dissociation from the manganese dimer, followed by metal-metal bond homolysis and subsequent reaction of the 15-electron intermediate, (Mn(CO)[sub]3PBu[sub]3, with benzyl chloride. The present work begins with the realisation that the previous data is also compatible with a radical chain process. In an attempt to distinguish between these two mechanisms, studies have been make of the variation in the quantum yield for the formation of (MnCl(CO)[sub]4PBu[sub]3) with benzyl chloride concentration. An examination of the reaction between (Mn[sub]2(CO)[sub]8DPPM) and benzyl chloride has also been carried out. Unfortunately, these studies still do not provide an unambiguous distinction between the mechanisms. (ii) A study has been made of the thermal reaction between (Mn[sub]2(CO)[sub]8a{PBu[sub]3}[sub]2) and benzyl and other halides. At 40 C the reaction is first order in both manganese dimer and benzyl choride and is not inhibited by added CO. This contrasts with that previously reported for the photochemical reaction and indicates that the thermal reaction follows a different pathway. Reaction of the metal dimer with 6-bromo-hex-1-ene suggests a free radical process and reactions with substituted benzyl bromides indicate an electron transfer step. Thus a mechanism is proposed involving electron transfer from the dimer to the organic halide, as the first step. Subsequent fission of the radical anion so formed into a halide ion and an organic radical, such as PhCH2, is followed by reaction of the dinuclear radical cation with the halide ion generating (MnCI(CO)[sub]4PBu[sub]3) and (Mn(CO)[sub]4PBu[sub]3). The manganese-centered radical then combines with the benzyl radical to yield (MnBz(CO)[sub]4PBu[sub]3). This reaction is thus a non-chain process. (iii) In view of the findings detailed above that (Mn[sub]2(CO)[sub]8{PBu[sub]3}[sub]2) reacts with benzyl chloride according to equation 1, it was deemed appropriate to examine the reactions between benzyl halides and a range of dinuclear metal complexes. The complexes studied were (M[sub]2(CO)[sub]10) (M = Mn, Re), (Mo[sub]2(CO)[sub]6Cp[sub]2), (Fe(CO)[sub]2Cp)[sub]2, (Fe[sub]2(CO)[sub]3PBu[sub]3Cp[sub]2), (Fe(CO){P(OMe)[sub]3}Cp)[sub]2 and (Co[sub]2(CO)[sub]6{PBu[sub]3}[sub]2), (Cp = D[sup]5-C[sub]5H[sub]5). Only (Fe[sub]2(CO)[sub]3PBu[sub]3Cp[sub]2) reacted with benzyl chloride under thermal conditions. All the dimers, except (M[sub]2(CO)[sub]10) (M = Mn, Re), reacted with benzyl bromide giving the corresponding bromo-complexes. Photochemical reactions with benzyl chloride were observed for all dimers except (Co[sub]2(CO)[sub]6{PBu[sub]3}[sub]2) and all, including the cobalt complex, reacted with benzyl bromide. In all cases, halo-complexes were formed, however, the observation of the associated benzyl complexes depended on both the benzyl halide and the metal dimer.

The effects of foliar applied urea and potassium chloride on the severity of leaf diseases of cereals were investigated in the laboratory, glasshouse and field between 1992 and 1995. Field studies with urea gave inconsistent results with respect to severity of Erysiphe graminis and consistently increased the leaf area affected by Septaria tritici. However, potassium chloride applied as a foliar spray consistently decreased the leaf area of wheat affected by E. graminis and S. trifid compared with equivalent applications of soil applied fertiliser. Disease control was achieved at early stem extension and after flag leaf emergence but yield responses were not detected. Laboratory investigations were undertaken to determine the mechanism by which foliar applied potassium chloride reduced the leaf area affected by E. graminis. The timing of application, within seven days pre or post inoculation, had no consistent effect on the efficacy of the fertiliser. Investigations using polyethylene glycol as a control showed that the percentage leaf area affected declined linearly as the osmotic potential of the solutions were increased. Light microscopy revealed that the germination of spores in solution and on treated leaves was reduced as the osmotic potential of the solutions were increased. Spores which did germinate developed normally but those on leaves treated with solutions of high osmotic potential rarely formed haustoria. This suggested a second mechanism acting inside the leaf. Multiple regression analysis of experimental data indicated that the inhibition of spore germination was the major response reducing the area of the leaf affected. Although the data were not conclusive it appeared that the increase in leaf water potential, following the foliar application of potassium chloride, was involved in the control of E. graminis.

One of the most important outstanding problems with the hydrometallurgy of copper is the low temperature leaching of chalcopyrite. In this thesis, a fundamental study at low temperature was undertaken in order to establish a mechanism, which is consistent with the data obtained in an extensive study of the kinetics of dissolution of several chalcopyrite concentrates. It will be demonstrated that enhanced rates of dissolution can be achieved at ambient temperatures by the application of controlled potentials in the range 560-650 mV, depending on the concentration of chloride ions. However, control of the potential by the use of electrochemical or chemical oxidation of iron(II) or copper(I) ions is ineffective unless carried out in the presence of dissolved oxygen. The rates of dissolution are approximately constant for up to 80% dissolution for sized fractions of the concentrates with an activation of energy of about 75 kJ mole-1. Chalcopyrite from different sources appears to dissolve at approximately the same rate which is largely independent of the iron and copper ion concentrations, the acidity and chloride ion concentration but depends in some cases on the presence of additives such as fine pyrite or silver ions. Based on the results of these leaching experiments and detailed mineralogical analyses of the residues, a mechanism involving non-oxidative dissolution of the mineral coupled to oxidation of the product hydrogen sulfide will be proposed. The latter reaction is shown to occur predominantly by a copper ion – catalyzed reaction with dissolved oxygen. The results of an independent study of the kinetics of this reaction will be presented which will demonstrate that the rates are consistent with those obtained for the dissolution of the mineral. The possible involvement of a covellite-like surface layer on the chalcopyrite under some conditions will also be discussed as it relates to the mechanism. It will also be shown that fine pyrite particles can also act as a catalyst surface for the oxidation of hydrogen sulfide. This mechanism is consistent with the mineralogy which confirmed the formation of secondary sulfur which is not associated with chalcopyrite but is associated with fine pyrite if present. A comparison of this mechanism with that proposed in other more limited studies of the dissolution of chalcopyrite under similar conditions in sulfate solutions has been made.

Designing durable concrete structures is becoming increasingly important with emphasis being placed on extending service life. This project focuses on the effect of low temperatures on chloride binding, chloride binding capacity and ion-binder interactions with respect to hydroxyl ions and pH. Three supplementary cementitious materials were used as well as two w/b ratios, and four curing times. The effect of temperature cycling on chloride binding, binding capacity and ion-binder interaction were also investigated. With temperatures decreasing from 23°C to -15°C, there is a decrease in bound chloride and chloride binding capacity, with GGBFS>GU>MK>SF being the order of binding. When temperature cycling was performed, the binding capacity changed depending on the exposure temperature, with warmer temperatures associated with higher binding capacities. When service life estimates were conducted using Life-365 software, it was found chloride binding capacities determined at 23°C may not be conservative when estimating service life in colder climates.

Designing durable concrete structures is becoming increasingly important with emphasis being placed on extending service life. This project focuses on the effect of low temperatures on chloride binding, chloride binding capacity and ion-binder interactions with respect to hydroxyl ions and pH. Three supplementary cementitious materials were used as well as two w/b ratios, and four curing times. The effect of temperature cycling on chloride binding, binding capacity and ion-binder interaction were also investigated. With temperatures decreasing from 23°C to -15°C, there is a decrease in bound chloride and chloride binding capacity, with GGBFS>GU>MK>SF being the order of binding. When temperature cycling was performed, the binding capacity changed depending on the exposure temperature, with warmer temperatures associated with higher binding capacities. When service life estimates were conducted using Life-365 software, it was found chloride binding capacities determined at 23°C may not be conservative when estimating service life in colder climates.

Concrete structures deteriorate in their operating environment under the combined action of harsh environmental conditions and external loading. Although the applied load can lead to a certain degradation of the structure, the main long-term deterioration mechanism involves moisture movement and the transport of chlorides within concrete. In order to build durable and reliable structures, it is necessary to be able to accurately predict the movement of moisture and chlorides within concrete.<p> In the case of unsaturated concrete, the transport of chloride ions is integrally associated with prediction of moisture fluxes in concrete. Even the diffusion of chloride ions depends on the degree of saturation of the concrete since concrete must have a continuous liquid phase for diffusion to occur. Therefore, simple diffusion theory, used in the current literature, is not sufficient to predict the diffusion of chloride ions in the case of unsaturated concrete. Most diffusion models described in the current published literature are applicable to concrete structures that are permanently wet and invariably underestimate the amount of chlorides penetrating the concrete of structures subjected to wetting and drying cycles. The research presented in this thesis reviews current knowledge, mathematical models and test methods pertinent to the movement of moisture and transport of chloride ions in unsaturated concrete.<p> A laboratory testing program was established to characterize the material properties of concrete mixes with water-cement ratios 0.4, 0.5 and 0.6. Concrete was characterized by its saturated hydraulic conductivity, moisture retention function and dependence of diffusion coefficient on degree of saturation. A geotechnical centrifuge was used to determine the saturated hydraulic conductivity of the concrete samples. Values of the saturated hydraulic conductivity of the samples were in the range of 10-11-10-12 m/s.<p> The moisture retention function of concrete samples was determined using a vapour equilibrium technique. The experimental moisture retention data was used to determine van Genuchten parameters for each of the concrete mixtures and subsequently used to determine the capillary pressure-degree of saturation relationship and relative permeability-degree of saturation relationship as a ``closed- form`` analytical expression. An electrical resistivity technique was used to determine the dependence of the chloride diffusion coefficient on the degree of saturation of the concrete. The result was compared with the Millington and Quirk model. Most of the experimental results should be useful to researchers in the field, as well as the engineering community at large, considering that they are rarely found in the concrete literature.<p> Simulations were made to determine the influence of various parameters measured during experiment on movement of moisture and transport of chloride ions in unsaturated concrete using TOUGH2, a multiphase, multicomponent, model that simulates coupled heat, moisture and salt transport in saturated and unsaturated rocks.

Concrete structures deteriorate in their operating environment under the combined action of harsh environmental conditions and external loading. Although the applied load can lead to a certain degradation of the structure, the main long-term deterioration mechanism involves moisture movement and the transport of chlorides within concrete. In order to build durable and reliable structures, it is necessary to be able to accurately predict the movement of moisture and chlorides within concrete.<p> In the case of unsaturated concrete, the transport of chloride ions is integrally associated with prediction of moisture fluxes in concrete. Even the diffusion of chloride ions depends on the degree of saturation of the concrete since concrete must have a continuous liquid phase for diffusion to occur. Therefore, simple diffusion theory, used in the current literature, is not sufficient to predict the diffusion of chloride ions in the case of unsaturated concrete. Most diffusion models described in the current published literature are applicable to concrete structures that are permanently wet and invariably underestimate the amount of chlorides penetrating the concrete of structures subjected to wetting and drying cycles. The research presented in this thesis reviews current knowledge, mathematical models and test methods pertinent to the movement of moisture and transport of chloride ions in unsaturated concrete.<p> A laboratory testing program was established to characterize the material properties of concrete mixes with water-cement ratios 0.4, 0.5 and 0.6. Concrete was characterized by its saturated hydraulic conductivity, moisture retention function and dependence of diffusion coefficient on degree of saturation. A geotechnical centrifuge was used to determine the saturated hydraulic conductivity of the concrete samples. Values of the saturated hydraulic conductivity of the samples were in the range of 10-11-10-12 m/s.<p> The moisture retention function of concrete samples was determined using a vapour equilibrium technique. The experimental moisture retention data was used to determine van Genuchten parameters for each of the concrete mixtures and subsequently used to determine the capillary pressure-degree of saturation relationship and relative permeability-degree of saturation relationship as a ``closed- form`` analytical expression. An electrical resistivity technique was used to determine the dependence of the chloride diffusion coefficient on the degree of saturation of the concrete. The result was compared with the Millington and Quirk model. Most of the experimental results should be useful to researchers in the field, as well as the engineering community at large, considering that they are rarely found in the concrete literature.<p> Simulations were made to determine the influence of various parameters measured during experiment on movement of moisture and transport of chloride ions in unsaturated concrete using TOUGH2, a multiphase, multicomponent, model that simulates coupled heat, moisture and salt transport in saturated and unsaturated rocks.

The objective of this study was to evaluate the effect of orally administered ammonium chloride (NH4CL) on pH and specific gravity of urine, overall gain, and water consumption in mature wethers on a grower/finisher ration. Obstructive urolithiasis, or urinary calculi, is a common problem in sheep and goat production systems utilizing a high grain diet, particularly one high in magnesium. Maintaining animals on a 70 to 90% concentrate ration is most conducive to the formation of urinary calculi. Boer cross wethers (n = 24) were stratified by body weight and randomly assigned within strata to one of three treatment groups. Wethers were placed on a common diet containing 2% NH4Cl during the three week collection period. Treatment consisted of daily oral dosages of 0g NH4CL (CON), 5.85 g NH4CL (TRT 1), or 13.8g NH4CL (TRT 2). Urine collected from TRT2 tested more acidic on the second and fourth collections before coming back linear constant with both the control (CON) and TRT1 . There was no effect of treatment (P < 0.001) on specific gravity of urine. Weight gain was greater (P < 0.01) in TRT1 (4.15 kg) and TRT2 (4.48 kg) as compared to CON wethers (2.95 kg). Water consumption was the most variable of all investigated objectives; all groups began with a linear increase for the first 4 d. Treatment 2 (P < 0.001) then showed significant increase at collections 2 and 4. Treatment 1 stayed more linear with the control with minimal increases (P < 0.001) occurring at periods of more acidic urine. This study indicates that administration of NA4Cl had minimal effect on urine pH, water consumption, and overall gain, but no effect on specific gravity.

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