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Investigation of the formation of complexes between selected organic compounds and the chlorides and sulphates of chromium

  • Authors: Ellis, Melville John
  • Date: 1961
  • Subjects: Organic compounds , Chromium compounds , Chlorides , Sulfates
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4466 , http://hdl.handle.net/10962/d1011744 , Organic compounds , Chromium compounds , Chlorides , Sulfates
  • Description: Some properties of soluble chromium complexions containing coordinated aliphatic acids have been studied. The work falls naturally into two sections. In the first, the coordination of a series of ⊄, β and⊁amino acids by chromium chloride has been studied by physical methods. The tanning action of chromium chloride in the presence of these amino acids has also been studied. The absorption spectra of the complexes were similar to those reported previously for trivalent chromium solutions, having two pronounced maxima in the visible region. From the variations in these absorption maxima, it is suggested that the absorption maximum in the 580 m u region is influenced by coordination of the chromium with the ligand, while the maximum in the 420 m u region is also affected by the olation of the basic chromium salts. The spectrophotometric evidence indicates that raising the pH or the concentration of the ligand in the solution increases the amount of coordination, and further, that the tendency for coordination increases as the hydrocarbon chain separating the carboxyl and amino groups becomes longer. This suggests that tho stability of the complex is not dependent on chelate ring formation, but is influenced by the pK₁ value of the carboxyl group of the . ligand. Potentiometric titrations support the hypothesis that only the carboxyl group is coordinated, to an extent depending on its pK₁ value, since the curves have shown that the amino group is still free to titrate. Paper electrophoresis has shown that all the complexes prepared were cationic, indicating that the amino acids were coordinated as dipolar ions. The tanning action of the masked chromium solutions has confirmed the deductions made from the physical measurements. Increasing the amount of amino acid added to the solution lowered the chromium fixation and the hydrothermal stability of the leather, and further, that for solutions at the same pH containing the same amount of masking agent, tanning action was least for the ⊁ amino acid and greatest for the ⊄ amino acids. Comparison of the present data with the corresponding results obtained with chrome alum solutions showed that coordination of the amino acids was greater in the case of the chromium chloride solutions. The second section of the experimental work was an investigation of the coordination of substituted acetic and propionic acids by chromium chloride and chromium sulphate. Spectrophotometric and potentiometric methods were applied and the various solutions were also used in miniature tanning experiments. Certain difficulties were encountered in the preparation of some of the complexes, and it was not possible to carry the work to a point where conclusive results could be obtained. Nevertheless, the work reported suggests that chelate ring formation occurs in the coordination of hydroxy-carboxylic acids, resulting in exceptionally high stability of the complex. In the case of the other ligands, containing amino, chloro and bromo groups, as well as with acetic and propionic acids, the results suggest that coordination involves the carboxyl group only, and that the pY value of this group is an important factor determining the stability of the complexes.
  • Full Text:
  • Date Issued: 1961

John X. Merriman : the making of a South African statesman (1869-1878)

  • Authors: Gruber, R F J
  • Date: 1961
  • Subjects: Merriman, John Xavier, 1841-1926 , Statesmen -- South Africa -- Biography , South Africa -- Politics and government -- 1836-1909
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:2623 , http://hdl.handle.net/10962/d1015002
  • Description: With the possible exception of Hofmeyr and Schreiner, there is no Cape statesman whose career raises more tantalising questions than that of John X. Merr1man. Last Prime Minister of the Cape Colony, doyen of Parliamentarians, brilliant orator, versatile administrator, veteran politician, his public life stretched across fifty-five years of south African History. He entered upon it before the grant of Responsible Government, the discovery of diamonds and gold, and the awakening. of Afrikaner Nationalism; he departed from it on the eve of the Statute of Westminster, the establishment of Iscor and the coming to power of Hertzog and Malan. His contemporaries looked upon him as a man of immense knowledge and olympian ability. In the eyes of many his position as leader of the largest and oldest settled community in South Africa, not to mention his role as heir to the Cape tradition, made him the natural choice as first Prime Minister of the Union he had helped to establish. He was not called to office. Barely seventy, in the full maturity of his years, he withdrew trom active political leadership in the country of his adoption. He is hardly remembered today. This thesis seeks to contribute something to an understanding of the man and an assessment of his qualities by a study of his formative years. It attempts both to reconstruct his personality and analyse the nature of his statesmanship - not only by an examination of the role he played in the years under review, but also by an assessment of the part he failed to play. For this purpose both the structure of Cape politics and the ramifications of the various problems that presented themselves have been explored in greater detail than might otherwise have been the case.
  • Full Text:
  • Date Issued: 1961

Kana ndoda

Kilnerton Training Institution - Graduation tea party, 1961

  • Date: 1961
  • Subjects: Kilnerton Training Institution -- Buildings -- Photographs Kilnerton Training Institution -- History -- Photographs Pretoria -- History -- Photographs Weaving Park, Pretoria -- History
  • Type: Image
  • Identifier: http://hdl.handle.net/10962/10788 , vital:21628 , PIC/M 5782
  • Description: The Kilnerton Training Institution, affiliated to the Methodist Church of Southern Africa, was established in 1886 in the small suburb of Weaving Park, Pretoria. The Institution was named after Rev. John Kilner, who encouraged the formation of an indigenous clergy in South Africa. The mission of the Institution was to provide seminary education to locals in preparation for ordination. In and above providing seminary education, Kilnerton also served as a primary and secondary school for children in the local community. The Institution is known for some of its illustrious past students, including Dikgang Moseneke (Deputy Chief Justice), Sefako Makgatho, Miriam Makeba, Lillian Ngoyi and Thomas Masekela. , This image is held at the Cory Library for Humanities Research at Rhodes University. For further information contact cory@ru.ac.za. The digitisation of this image was made possible through a generous grant received from the Andrew W. Mellon Foundation 2014-2017.
  • Full Text: false
  • Date Issued: 1961

Kuyaura kweasina katura

Lesiba

Lesiba

Letter from P.C. Kruger

Lion

Lion hunting song

Lion sounds

Lioness

Lioness Sounds

Loeriesfontein 3018

Lucan, poet of freedom : inaugural lecture delivered at Rhodes University

Mai tswapiguruwe

Melville Park Farm

Miningwa, Miningwa chaenda mudondo

Njari

Nyere yendongi ino rira

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