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Studies in the general field of gas chromatographic analysis have been made and some of the methods developed have been applied to a kinetic investigation of the reactions of methyl radicals with butene-1. In Part I the developments in the field of gas chromatography are described. An all-metal thermal conductivity cell with platinum sensing elements has been designed and constructed. Excellent compensation for the resulting changes of flow rate of the carrier gas was attained in analyses with rising column temperature. The use of thermistors as sensing elements in such cells was also studied. The influence of polarity of the stationary phase on relative retention volumes in gas partition chromatography was investigated in conjunction with the analysis of a complex mixture of organic sulfur compounds. Satisfactory separations of hydrogen sulfide, methyl mercaptan, ethyl mercaptan, methyl sulfide, propyl mercaptan, ethyl sulfide, thiophene and dimethyl disulfide were obtained. Isopentane and n-pentane were included for purposes of comparison. Irregularities were observed in relating retention volumes to boiling points for some of these compounds. Reversal of normal elution order within groups of compounds with different columns was related to the polarity of the column and the polarisability of the eluents. A high-sensitivity ionization gauge detector for gas chromatography was developed. By keeping the grid potential below the ionization potential of helium the device is sensitive only to the eluted compounds in the gas stream. Sensitivities from 100 to 500 times greater than those of thermal conductivity cells were observed. Only a small fraction of the gas stream emerging from the column is sufficient for detection purposes, and the device is insensitive to temperature and flow rate changes. Significant advantages may be obtained from the application of the newly developed ionization gauge detector to displacement chromatography because of the possibility of distinguishing between isomeric organic compounds. Results obtained with gas chromatographic methods without the use of a carrier gas are reported. A partial separation of a mixture of volatile organic compounds was obtained. The ionization gauge detector may be useful in the development of this method. In Part II the results obtained from the reaction of methyl radical with butene-1 are described. Alumina, squalane-pelletex, and tricresyl phosphate columns were used for the gas chromatographic analysis. Mass spectrometric identification of products was done where necessary. In the temperature range 160 to 220°C with di-t-butyl peroxide as the methyl source the following reaction products were identified: methane, ethane, 3-methyl-butene-1, pentene-2, n-pentane, isopentane, 3-methyl-pentane, and acetone. A mechanism accounting for the formation of these products and supported by kinetic evidence is presented. The butenyl and pentyl radicals formed in the reaction are stable near 200°C. Butenyl radical does not abstract hydrogen from butene-1 near 200°C, but combines with methyl to yield pentene-2 and 3-methyl-butene-1. The energy of activation for the formation of 3-methyl-butene-1 is from 2 to 4 kcal/mole higher than for the formation of pentene-2. Hydrogen abstraction by pentyl radicals from butene-1 gives n-pentane, and isopentane. The reactivity of the branched radical •CH₂CH[CH₃]CH₂CH₃ in hydrogen abstraction is twice as great as that of the straight chain radical CH₃CH₂CHCH₂CH₃. From material balances obtained it was found that 60 to 80% of butenyl, and from 7 to 30% of pentyl radicals are removed from the system by reactions other than combination with methyl and hydrogen abstraction in the case of pentyl. The disproportionation of pentyl radicals to pentane and pentene was unimportant in the present system. At 450 and 492°C methyl radicals do not sensitize the formation of the cyclic reaction products which were observed by other workers in the unsensitized pyrolysis of butene-1 at temperature near 500°C. The main reaction product of methyl with butene-1 at 450 and 492°C was found to be butene-2. The isomerization to butene-2 in the unsensitized reaction is a chain process with chain length increasing with temperature reduction. The mechanism of the chain reaction of isomerization is postulated to be: CH₂=CHCH₂CH₃ → CH₃ • + CH₂ = CHCH₂ • / CH₃ • + CH₂=CHCH₂CH₃ → CH₂=CHCHCH₃ + CH₄ / CH₂=CHCHCH₃ ↔ •CH₂CH=CHCH₃ / •CH₂CH=CHCH₃ + CH₂=CHCH₂CH₃ → CH₃CH=CHCH₃+ CH₂=CHCHCH₃. The chain length at 450°C was found to be 12.6, and at 492°C as 2.3. / Science, Faculty of / Chemistry, Department of / Graduate

I. In a special form of micro gas analysis apparatus the following methods may be used to obtain quantitative separations. Carbon dioxide can be removed at 70°C. by absorption in a mixture of sodium, potassium, and lithium hydroxides. Hydrogen, in the presence of carbon monoxide and methane, can be removed by diffusion through a palladium tube at 325°C; no irregularities occur at this temperature. Carbon monoxide is quantiatively oxidized by a mixture of silver oxide and hopcalite at room temperature. Acetylene is removed by condensation in liquid air. II. The surface of an activated carbon may be oxidized by water at room temperature. The reaction produces at least 1.92 micromols of hydrogen per gram of carbon. An equilibrium is established between the hydrogen, water, and the surface complex, after relatively long periods of time. The nature of the complex is not indicated. / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

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Numerous informal houses have been built on and adjacent to a landfill in iBayi, Port Elizabeth, South Africa, which accepted domestic and industrial waste. Formal housing surrounds most of the site at a greater distance - some 60 m, or further, from the landfill. Both formal and informally housed residents complain of odours, burning eyes, sore throats and headaches - symptoms which they believed were caused by the landfill. The landfill gas and ambient air were analyzed to classify and quantify the VOCs (volatile organic compounds) emitted and then to compare the quantitative data with recognised standards to establish if the residents are at risk. Eighteen target (potentially hazardous) VOCs were quantified. A wide variety of compounds were detected in both the ambient air and landfill gas. The results of the VOC analyses were similar to those of other workers in both the qualitative and quantitative studies. The concentrations of the VOCs were mostly lower than the TLV (threshold limit values) values, but exceeded the MRLs (minimum recommended levels). The combined concentrations of the VOC’s in the ambient air either approached or exceeded the limit values for combined exposure thus indicating that a potential health hazard exists. One third of the VOCs were detected in both the ambient air and the subsurface gas, however, external pollution sources also appear to contribute to the VOC concentrations ambient air. Dangerously high methane concentrations were repeatedly detected in the landfill gas amongst the informal houses. There was a vast improvement in the aesthetic qualities of the landfill since the disposal restriction to accept only domestic refuse and building rubble in July 1997. The ambient air was less odorous and landfill site littered. Fewer informal recyclers were present and their concomitant squabbling over valuables had almost vanished. The management of the iBayi landfill holds much room for improvement. There is potential for serious injury or even death if no action is taken to remedy the problems at the iBayi landfill. A holistic solution will have to be found to make the landfill a safe neighbour. Some complementary analyses (such as pH, heavy metal concentrations in the water and sediments etc.) were performed on the leachate and water surrounding the landfill.