An investigation of the orientation of certain long-chain fatty acids at the air-water interface
- Authors: Saayman, Henry Martin
- Date: 1962
- Subjects: Fatty acids , Surface chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4496 , http://hdl.handle.net/10962/d1013117
- Description: 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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- Date Issued: 1962
The oxalate complexes of thorium
- Authors: Phillpotts, Charles Adrian Richard
- Date: 1962
- Subjects: Oxalates , Thorium , Complex compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4488 , http://hdl.handle.net/10962/d1013029
- Description: (1) The ammonium, potassium and sodium salts of three complex thorium oxalates were prepared and studied. (2) Their solubilities and conditions of stability were studied. (3) The reaction between thorium and excess oxalate, and vice versa, was studied by means of conductivity and high frequency conductivity measurements. (4) The formation constant of Th(C₂O₄)₄⁴⁻ and Th(C₂O₄)₃²⁻, and the solubility product of (NH₄)₂Th₂(C₂O₄)₅, were determined by a solubility method.
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- Date Issued: 1962
The solubility of mercurous chloride in water at 25°C
- Authors: Clur, Dennis Alwin
- Date: 1959
- Subjects: Mercury compounds -- Solubility , Mercuric chloride
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4522 , http://hdl.handle.net/10962/d1014705
- Description: [From Introduction]. In 1955, Dry and Gledhill, both formerly of this Department, published their paper on the Solubility of Mercurous Chloride in Water at 25°0, and it was originally intended that this thesis should be an extension of the study to cover the temperature range from 5 t o 55°0. A preliminary investigation at 25°0, however, failed to yield results which were consistent with their findings, even though their apparatus and experimental technique were used. In an effort to resolve these difficulties their method of saturating the calomel in the conductance cell was thoroughly investigated, and as this procedure was found to be responsible, it was necessary to evolve an entirely new approach. The technique finally adopted was to saturate the mercurous chloride solutions by mechanical stirring in siliconed vessels and to carry out the conductance, pH, and total mercury concentration measurements on the filter ed solution. This method gave good results, and was free from the many extrapolations prevalent in the original procedure.
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- Date Issued: 1959
The anodic oxidation of calcium lactate : an estimation of the products of electrolysis and an investigation into some of the problems involved
- Authors: Impey, Norman Robert Murray
- Date: 1949
- Subjects: Electrolytic oxidation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4480 , http://hdl.handle.net/10962/d1012556 , Electrolytic oxidation
- Description: The subject of this thesis was chosen originally as a result of a suggestion made by a manufacturer of lactic acid. Lactic acid is made by a fermentation process from molasses and the acid is extracted from the fermentation liquors as calcium lactate. The conversion of the calcium lactate back to lactic acid is a tedious process from an industrial point of view. It was therefore suggested that the conversion may be more easily accomplished by electrolysis. The first experimental work was conducted with this object in view, but it soon became apparent that it was unlikely that lactic acid could be produced in suitable quantities for industrial purposes by this means. There was no reference in the literature to the electrolysis of calcium lactate, and little reference to the electrolysis of lactates in general, and what there was appeared to be conflicting, so it was decided to continue the investigation into the subject in order to determine what are the products of the anodic oxidation of calcium lactate. Intro., p.1.
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- Date Issued: 1949
The construction of a precision conductance bridge and its application to a study of chromium sulphate complexes
- Authors: Goddard, Errol Desmond
- Date: 1949
- Subjects: Chromium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4476 , http://hdl.handle.net/10962/d1012038 , Chromium
- Description: A constant temperature room employing the comparatively new method of temperature control by means of a thyratron relay has been constructed. A high precision conductance bridge has been built in a very convenient form. Improvements include the incorporation of a cathode ray oscilloscope as null detector and the inclusion of a very stable oscillator of the phase shift type which is capable of giving a very pure wave form. Tests carried out on a system of degenerative tuning showed the the system is not easily applicable to high gain amplifiers. A new form of conductometric titration cell, employing the dipping type electrodes has been designed with special precautions against possible Parker Effect. A series of tests has been carried out on three types of cell to ascertain the effects of absorption, polarisation and Parker Effect on the accuracy of an ordinary conductometric titration. Conductometric titrations of NaOH solutions of violet and green chromic sulphate has been carried out, and the effect of aging these solutions closely studied. In addition, conductometric titrations of BaCL₂ into the chromic solutions have been made, and the NaOH titrations have been studied potentiometrically as well.
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- Date Issued: 1949
A study of the errors involved in the sampling of soils
- Authors: Steyn, Willem Johannes Abraham
- Date: 1945
- Subjects: Soils -- Analysis , Soil chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4505 , http://hdl.handle.net/10962/d1013290
- Description: The importnnce of representative soil sampling is now beginning to receive more general recognition. The analysis of the sample, and any chemical or physical treatment it may undergo in the laboratory, is of little practical value if it is not known with reasonable certainty that this sample represents fairly the area from which it as taken. It has been said over and over again, that the existence of the world's whole civilization is dependent upon a mere strip of soil, only 9 inches in depth. The study of the soil is therefore of special importance if only for the practical end of replacing any nutrient deficiencies which may be found. Intro., p. 1.
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- Date Issued: 1945