Liquid menisci in small pores exhibit a curved surface across which there is a significant pressure difference. The capillary properties of such surfaces are important in many areas of science and technology. Pores of uniform section can be broadly classified according to whether the perimeter is smooth (as in cylindrical tubes) or angular (as in triangular tubes). A meniscus that is entirely bounded by the pore walls has a curvature that is inversely proportional to the tubes' hydraulic radius. A meniscus in an angular tube, however, has liquid wedges in the corners and this reduces the effective area of the pore. In the past it has been difficult to calculate the curvatures, of this class of menisci. Some recent studies have shown that a relatively straightforward, but hitherto neglected, method originated by Mayer & Stowe (1965) and Princen (1969a) can be applied to analyse wedging menisci. However, the method has lacked a comprehensive experimental verification. This investigation follows on from the previously limited studies. A standardised method for the application of the analysis is described, the results from which are compared to observations made using modified experimental procedures. The behaviour of the capillary surfaces formed in several model pores are analysed with the method. The model systems studied are rectangular ducts, the pores formed by a rod in an angled corner, by two contacting rods and a plate and the space between a rod and a plate. For the latter two shapes the analysis is extended to include systems of mixed wettability which have a particular bearing on enhanced oil recovery operations. Experiments in which curvatures are inferred from observations of capillary rise, are performed using two comparative techniques. An involved procedure confurns predictions of meniscus curvature to within 0.3%. Use of a more straightforward, though less accurate, technique enables variations of curvature with tube shape or contact angle(s) to be conveniently studied. Results obtained are excellent and confmn the theory within the determined experimental errors. In addition the analysis has been extended to predict more complex meniscus behaviour. The tubular space formed by three rods and a plate gives rise to a whole family of meniscus shapes. With certain geometries a capillary surface regards the tube as a pore doublet where the behaviour in one neighbouring pore depends on that in the other. The capillary properties of this model system shed light on the behaviour of adjacent pores in a porous medium undergoing drainage (ordesorption). Experiments show excellent agreement with predictions of meniscus shapes, curvatures and, most interestingly, points of spontaneous transition from one meniscus shape to another. The system also has a potential future application because one panicular arrangement of rods produces a meniscus with a curvature virtually independent of the geometry. This makes it suitable for producing a standard meniscus of known curvature.

The adsorption of iodine on a platinum(111) single-crystal surface has been investigated using LEED, Auger spectroscopy, and work function measurements. The phase transformations and work function changes have also been measured during desorption. Mass spectroscopy shows that above 300 K the main desorption product is atomic iodine with a small amount of molecular iodine detected as well. The desorption kinetics at these temperatures were studied by different techniques to extract the kinetic parameters and the orders of the desorption reactions. There are two main desorption features, one displaying zero-order desorption kinetics typical of a phase transition and the other displaying first-order kinetics with a coverage-dependent activation energy. The work function changes during adsorption and desorption were shown to be a function of coverage rather than having a site dependence. The adsorption of iodine at temperatures below 200 K was also studied. Multilayers of molecular iodine are formed that desorb with essentially zeroth order kinetics. Two multilayer desorptions were observed with thermal desorption spectroscopy. One of the multilayer desorptions had a significant work function change associated with it. The work function changes were modelled by calculating the hybridization dipole moment using extended-Hückel theory with Bloch wavefunctions. The calculations are sensitive to the atomic position of the adsorbate and require further refinement. Due to the protective nature of the iodine layer and its high polarizability, the iodine layers were used to study the ambient pressure adsorption of fluorinated carbosilane dendrimers. These dendrimers are stable in vacuum but do not form an ordered structure at ambient temperature. Heating the adsorbed dendrimer in vacuum to 1100 K produced a new ordered structure on the platinum surface. This structure was shown not to be an intact dendrimer molecule as two different dendrimers with similar structural moieties produced the same (√19x√19)R23.4° LEED pattern. The ordered structure was studied by Auger spectroscopy to determine the carbon coverage. This structure is proposed to be islands of a coincidental lattice of graphite. / Graduate

Ph.D. (Chemistry) / This work describes the activation by steam, carbon dioxide, or air of specially prepared cane sugar and commercial carbon granules. The following determinations were done on these carbons. Densities in various fluids, crushing strengths (utilising an arbitrary developed method), chemical composition, surface appearance (from electron micrographs), and low temperature isotherms (utilising three volumetric methods)...

The results obtained for the cross-sectional areas of the series of long-chain fatty acids may best be summarized with the aid of Graph 9. This graphical representation of the molecular areas, in Ų , against the chain length (n), of the fatty acid molecules, illustrates variation of the areas with chain length for the series in recrystallized form, and also for selected samples in the zone purified and vacuum distilled forms. On the graph, the limits of variation of the molecular areas have been represented as lines of a length corresponding to twice the standard deviation (2S). This is to give representation that the standard deviation may be positive or negative in relation to the mean. For molecules with n odd and lying between 15 and 19, the molecular area decreases. This may be due to the effect of 3 factorsg (1) A general decrease in lateral translation because of the increasing molecular mass (translational kinetic energy per molecule = ½ mc ⁻²), resulting in closer spacing of molecules. (2) A general, but steady decrease in the angle of tilt of the molecules which thus tend to be held more erect in the condensed film. (3) A general decrease in the precessional motion of the hydrophobic chain groups. For molecules with n odd and between 19 and 23, the molecular areas increase probably due to the steady increase in molecular mass causing the long chains to commence to buckle, tilt or topple in their upper regions. This tilting becomes greater because of the increasing gravitational effect on the heavier molecules which tends to make them assume a flatter posture in relation to the surface. The lower values observed for margaric and nonadecanoic acids, may be due to increasing symmetry in the chain, with corresponding economy in packing in condensed monolayers. This effect may be connected with increasing cylindrical symmetry of the hydrocarbon chain for even values of n. The results of this investigution, incomplete as it is, - serve to indicate what might reasonably be expected to happen in the orientation of these fatty acids in monolayers. Further work, especially on a greater range of acids with even n, is clearly necessary in order to establish the tentative ideas which have been suggested. However, in the present research, work was limited to those acids in the series which were obtainable without undue difficulty or delay, those which would spread readily under the conditions of experiments carried out at 20°C, and those which could be purified relatively easily. The acids below n = 15 in the series were found to be too soluble in aqueous substrates, at operating temperatures of 20°C, to yield reliable evidence with the Langmuir trough technique. The acids above n = 23 were unobtainable commercially and the synthesis of those acids from the lower members in the series presented problems of isolating the required specimens and difficulty in purifying these, which were considered b be beyond the scope of the present research. Summary and conclusion, p. 122.

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