An investigation of certain complex ions of trivalent chromium by spectrophotometric and other physical methods
- Authors: Burley, Ralph Walter
- Date: 1950
- Subjects: Chromium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4521 , http://hdl.handle.net/10962/d1014675
- Description: Although chromium coordination compounds are of considerable technological importance, they have been subjected to few thorough investigations since Werner's original experlments, in spite of the fact that we now possess a number of accurate physical methods, not available in Werner's time for the study of coordination complexes, The object of the work described in this thesis was to obtain further information on the chemistry of complex chromium(III) ions with special reference to the dioxalato-diaquochromiate system, [Cr(C₂0₄)₂(H₂0)₂]. For this purpose; spectrophotometric and potentlometrlc measurements were combined to yield information on a number of topics, The spectrophotometric investigations consisted in measuring the absorption spectra of the potassium salts of the complexes under consideration and in observing the changes in light absorption which occur during their formatlon and decomposition. The instrument used was a Beckmann Quartz Spectrophotometer model du. More than than twelve new absorption spectra were measured in this work and in conjunction with the spectra of other chromium and cobalt complexes reported by earlier workers, these are used to review the position of spectrophotometry as a method of investigating chromium complexes. The reasons for the shapes of the absorption spectra are discussed and it is concluded that spectrophotometry is useful for observing the progress of reactions involving complex ions and for analysing solutions, but that more fundamental data cannot be expected from the absorption curves.
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Studies in the plant ecology of Fern Kloof near Grahamstown
- Authors: Seagrief, S C
- Date: 1950
- Subjects: Plant communities -- South Africa -- Eastern Cape , Plant ecology -- South Africa -- Eastern Cape , Plants -- South Africa -- Eastern Cape , Forest ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4267 , http://hdl.handle.net/10962/d1014299
- Description: The area studied at Fern Kloof, near Grahamstown, consists of a strip of vegetation approximately 260 yds. long and 50 yds. wide, in which there are two communities: 1) indigenous forest 2) exotic Pine forest (which has only one tree species Pinus pinaster). Throughout the thesis this species is referred to as the pine. The object of the investigation has been to determine whether these communities are natural or not. This has involved a study of the floristic composition, the life forms and the structure of the plant communities. In addition, various soil and environmental factors have been studied.
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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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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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A critical evaluation of the analytical method used for the separation and estimation of copper and nickel
- Authors: Sismey, J E
- Date: 1948
- Subjects: Copper -- Analysis , Nickel -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4519 , http://hdl.handle.net/10962/d1014335
- Description: [From Introduction]. This thesis deals with the determination of copper and nickel both separately and in each other's presence. The work is divided into two sections, one of which treats the subject from the theoretical side while the other contains an account of the practical work performed by the author. In the theoretical section, an attempt is made to summarise the better-known methods for the determination of copper and nickel, and at the same time, to incorporate such improvements, criticism and variations as have appeared in the literature. The subject is so vast that its summary in so short a space must necessarily be incomplete. Yoe and Server, for example, quote 111 references on the subject of the nickel-dimethylglyoxine with other ions. Only a fraction of the literature was available, and space permitted only a fraction of this to be abstracted in the following pages.
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The oxidation and degradation products of black wattle tannin (Acacia mollissima)
- Authors: Heugh, Richard Anthony
- Date: 1948
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21169 , http://hdl.handle.net/10962/6706
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A preliminary investigation of the determination of ionic mobilities by conductometric titration
- Authors: Festenstein, Gerald Norman
- Date: 1947
- Subjects: Ionic mobility , Conductometric analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4472 , http://hdl.handle.net/10962/d1011810 , Ionic mobility , Conductometric analysis
- Description: The determination of ionic mobilities by conductometric titration was first suggested by Barker, Rowler and Shuttleworth in discussing the theory of conductometric titration of acids, bases and neutral salts. Intro. p. 1.
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A study of the comparative anatomy of the lateral compound eyes of arthropods
- Authors: Glaholm, J
- Date: 1947
- Subjects: Arthropoda -- Anatomy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5908 , http://hdl.handle.net/10962/d1014966
- Description: In this thesis the interest has centered mainly on the comparative anatomy of the lateral eyes of Arthropods especially the compound eyes, with some particular reference to those of Chilopoda. The comparative anatomy of the eyes of Chilopoda seemed to be of interest, since they possess in most cases simple lateral eyes, which are not characteristic of the adults of any other group of Arthropoda, except Arachnids, to which the Chilopoda are only remotely related In a few cases - in the Scutigeridae - "compound" eyes are present, which are very unusual in their internal anatomy. The following possibilities with regard to the relationships of the Chilopod eyes present themselves. The simple eyes may be the products of degeneration of a compound eye. Alternatively they may be ocelli of a very primitive pre-compound eye type, persisting where in some cases a compound eye has failed to develop. As a third possibility they may have been separately evolved in forms, in which the compound eye was lost or failed to develop. In the last case they would appear to be unrelated to those of any other Arthropods, except possibly those of Diplopods, to which they are very similar in structure. The "compound" eyes may be or the same type as the compound eyes in the remaining Arthropods, with the differences due to degeneration, or to specialisation. Alternatively they may be of a separate type and formed secondarily, either as a single new structure. or a coalescence of ocelli. The enquiry into the interrelationship of these eyes and their relation to the eyes of other Arthropoda raises several points for investigation. For the compound eyes it is necessary to decide whether they were primarily present in the ancestors of some or all of the classes or Arthropods, and whether they have a common or more or less diverse origin with some evolutionary convergence. For the lateral simple eyes it is necessary to decide whether there are any indications in phylogeny, ontogeny or anatomy of the primitive or secondary formation of a compound eye by the aggregation of numerous ocelli or the elaboration of one or these. Such information might be expected to throw light on the origin of the Scutigerid eye. Alternatively any indications of the formation of simple from compound eyes might show whether the Chilopod simple eyes could have evolved in this way from a Scutigerid or some other compound eye. Median eyes are present in some Trilobites, Eurypterida, Crustacea, Hexapods and Arachnida. Although they exhibit considerable variations in structure, they are all clearly simple eyes. As they are absent in Chilopoda and in the remaining Arthropods are entirely separate in origin from the lateral eyes, with a separate seat of innervation, their comparative anatomy is of little interest in this case. The main portion of the thesis deals with the comparative anatomy, origins and relationships of the different types of compound lateral eyes. The second part comprises a short appendix dealing with similar aspects of the lateral ocelli. Detailed descriptions and figures have been given for the eyes of eight species. Some mention is also made of points observed in the internal or external anatomy of species which were studied in less detail. The theoretical conclusions are based on material from the available literature and from these descriptions.
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The high pressure catalytic hydrogenation of the tannin of black wattle (Acacia mollissima Willd)
- Authors: Silk, M H
- Date: 1947
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21132 , http://hdl.handle.net/10962/6528
- Description: From Introduction: The wattle industry in South Africa has, from its commencement in the middle of the last century, gradually assumed a position of increasing importance in the economic structure of the country. Apart from the provision of a valuable tanning extract for home use and for export, the tree itself has proved of considerable importance to the Union’s mining industries. In addition there would appear to be possibilities for the utilisation in the near future, of the raw ground bark and the wattle extract for the manufacture of a number of by-products, including certain types of plastics.
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Base exchange in soils : a study of the reproducibility of base exchange values for some South African soils, as indicated by leaching with normal ammonium acetate solution
- Authors: Pienaar, D J
- Date: 1946
- Subjects: Soil chemistry , Soils
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4489 , http://hdl.handle.net/10962/d1013038
- Description: A very reliable method for the total analysis of the ammonium acetate leachate has been outlined. This is both simple and straight forward and is more rapid than any which have been seen in the literature. It is particularly applicable where a worker must perform a large number of routine analyses in the minimum of time. Shirley (29) and other workers have shown that 1000 ml. of leaching solution is generally necessary to extract all the exchangeable gases. The present investigation has shown that the time of leaching makes no appreciable difference to the amounts of bases replaced, as long as this exceeds four hours. Two alternative methods have been introduced for the rapid determination of the total exchangeable bases in a soil and there are considered to be more reliable than that of Bray and White. It is suggested that the two new methods might yield a still greater degree of accuracy if larger aliquots were to be used for each determination. It is further pointed out that the values obtained by the chloride methods are more likely to represent correct values than the sum totals of the bases as determined individually, since these are arrived at by summing the results of four different estimations, each of which is liable to experimental error, whereas in the chloride methods there is only one perfectly straightforward determination. The values for the total exchangeable bases in the soils examined were found to vary over the range 2.50 to 14.28 m.e. per 100 g. soil, with a variance of up to ± 0.2sm.e. per 100 g., corresponding to a percentage error of up to ± 4.7%. These figures are based on the analysis of 12 separate leachings of each soil with normal ammonium acetate solution of pH 7.00. This rather wide variance can be attributed to the fact that the exchangeable bases in some soils are more easily replaceable than in other soils. It is regretted that the shortage of time and the non-availability of a complete range of samples of all typical South African soils has prevented the attainment of an original objective, namely, a statistical evaluation of the base exchange figures for all South African soil types. It would also have been of great interest to have been able to establish exactly the composition of the double salt of calcium and magnesium, whose existence has been postulated to explain the effect of the Ca/Mg ratio on the results yielded by the first chloride method. Summary, p. 67-68.
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The morphology and biology of Anomala vetula Wied : an arthropod pest of turf in South Africa
- Authors: Bradford, B
- Date: 1946
- Subjects: Anomala
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5903 , http://hdl.handle.net/10962/d1013545
- Description: From Introduction: For the past eight years, the Zoology Department of Rhodes University College, in co-operation with African Explosives & Chemical Industries Ltd., has been studying certain entomological problems relating to turf on the golf course along the coastal belt of the Eastern Cape Province. The position is briefly as follows:- On the golf courses at Mossel Bay, Humewood (Port Elizabeth), Port Alfred and East London, vast damage has been done to the greens and fairways by "white grubs", the larval stages of Scarabaeidae. It would appear that these beetles had been present in the environs of the courses for many years, but it was only when large areas of the natural veld were converted into fairways, with a more or less uniform cover of grass, with Cynodon dactylon Pers. predominating, that conditions were inadvertently created which favoured the development of the beetles. It was not long after the establishment of these golf courses, that the beetles assumed the proportions of a pest, and the larvae began destroying the root system of the grasses covering the greens and fairways.
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A preliminary investigation of the chemical nature of wattle tannin
- Authors: Corbett, John Henry
- Date: 1945
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21062 , http://hdl.handle.net/10962/6201
- Description: From Introduction: Although the tannins of wattle bark extract are generally considered to be of the class known as condensed tannins, a review of the general chemical nature of the tannins is given for the sake of completeness. This constitutes Part I of the thesis. Part II describes the preliminary investigation of the chemical nature of black wattle extract.
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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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The determination of selenium and tellurium in blister copper and copper concentrates
- Authors: Gray, Douglas James Skirving
- Date: 1940
- Subjects: Selenium , Tellurium , Copper
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4478 , http://hdl.handle.net/10962/d1012090
- Description: Selenium and tellurium do not occur to any great extent in Nature and they are seldom studied in any detail. However, a general understanding of their properties, both physical and chemical, is essential in an investigation of their analytical determination. A general account may be found in many of the text-books on inorganic chemistry, but the following resumè has been included in this dissertation for the sake of completeness.
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A polarographic study : the estimation of sodium and potassium in the presence of each other
- Authors: Carter, Austin John
- Date: 1938
- Subjects: Polarographs , Polarography , Potassium , Sodium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4455 , http://hdl.handle.net/10962/d1010434
- Description: The polarographic method has been described, and an attempt made to describe the difficulty of the simultaneous deposition of sodium and potassium. Various methods have been examined, of which precipitation of potassium with magnesium dipicrylaminate seems the most promising. The quantitative results were unsatisfactory, and possible sources of error are discussed. The method, while very convenient, rapid and labour-saving, is not sufficiently standardised to be trustworthy.
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An anatomical investigation of jointed cactus (Opuntia aurantiaca, Lindley) with germination tests, and observations on the movements of the stomata
- Authors: Archibald, E E A
- Date: 1936
- Subjects: Cactus -- Anatomy , Opuntia , Stomata , Germination
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4264 , http://hdl.handle.net/10962/d1013444
- Description: From Introduction: In 1934 the Government started an active campaign on the eradiction of Jointed Cactus. This plant was causing considerable damage to the farms and commonages of the Eastern Province, and was spreading at an alarming rate. The Officer in Charge of eradication, Mr E. du Toit, was stationed at Grahamstown which is fairly centrally situated in the infested area. In 1935 Dr A. Leemann of the Division of Plant Industry made his headquarters at Rhodes University College.
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Crocidolite in the districts of Prieska and Hay
- Authors: Schoeman, H E
- Date: 1930
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/6539 , vital:21133
- Description: From Introduction: The belt of hilly country extending from the southern extremity of the Doornbergen, through Prieska, Niekerkshoop, Griquatown and Kuruman, to a point far north or the latter, constitutes a region or great scientific and economic interest. Spoken of generally as the “Blue Asbestos Belt”, it has ramifications stretching in north, and north-westerly directions from Prieska. In the south it is known as the Doornbergen, passing into the “Asbestos Mountains” north of the Orange River, while farther north it becomes the Kuruman Hills. This large area is unique in that enormous deposits of fibrous crocido1ite or "blue asbestos" are known to occur scattered more or less irregularly over the entire belt. The mineral, often accompanied by some or all of its variations and alteration products, has been reported from nearly every farm, excepting only that portion covered by Ongeluk Volcanics, and the UPPER BEDS OF THE LOWER GRIQUATOWN SERIES, which thus form the only interruption to an otherwise unbroken extension of crocidolite bearing strata.
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Clays derived from the Lower Dwyka Shales, occurring in the vicinity of Grahamstown
- Authors: Blignaut, J J G
- Date: 1928
- Subjects: Clay -- South Africa -- Grahamstown Clay -- Economic aspects -- South Africa -- Grahamstown Geology -- South Africa -- Grahamstown Mineralogy -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4935 , http://hdl.handle.net/10962/d1005547
- Description: The Lower Dwyka Shales in South Africa oocur south of latitude 32⁰; resting conformably upon the Witteberg quartzites, which extend as coastal mountain rangee along the length of the South Coast. The shales, being less resistant to weathering than the quartzites below, and the Dwyka Tillite immediately above, are consequently found in valleys between these two formations. In one of these valleys Grahamstown is situated; where the Lower Dwyka Shales have been eroded by the various rivulets forming the eource of the Blaauwkrantz River. A geological map of the country round Grahamstown was prepared in eome detail, showing all the various rock formations occurring in the area, the full extent of the Lower Dwyka Shales being mapped with the Dwyka Tillite and the Witteberg Quartzite along its margins. The map includes an area of about six miles by three, with the Cathedral spire occupying an approximately central position, and is prepared on a scale of 5.65 inches to one mile. Traversing was done by means of prismatic compass and pacing.
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