1. Polarographic and spectrophotometric methods for the determination of molybdenum were reviewed. 2. The inclusion of salicylaldoxine in several supporting electrolytes was examined with a view to developing a polarographic procedure, suitable for routine analyses, which did not necessitate a preliminary time-consuming separation stage. A stable molybdenum wave was obtained from an electrolyte having a composition similar to the test solution obtained after the wet digestion of plant material. The height of the wave was found to be, over an optimum range, independent of the reagent concentrations. The wave was however distorted by a maximum, which rendered it unsuitable for quantitative analytical application. 3. The spectrophotometric procedure for molybdenum using thiocyanate is virtually specific and was examined critically. Modifications were found to improve the sensitivity of the procedure, and the stability of the chromatic compound. 4. The modified spectrophotometric procedure is recommended for the routine determination of molybdenum in plant material.

Call number: LD2668 .T4 1955 W43 / Master of Science

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

No description available.

In this study, two plant species, Schefflera umbellifera (Araliaceae) and / Thesis (M.Sc.) - University of KwaZulu-Natal, Pietermaritzburg, 2007.

This work is an account of the extractives from one member of the Meliaceae and one member of the Ptaeroxylaceae. In all, thirteen compounds have been isolated, of which four have not been described previously. Neobeguea mahafalensis belongs to the Neobeguea genus and has been classified into the Swietenieae subfamily of the Meliaceae. Neobeguea mahafalensis seeds obtained from Madagascar were investigated for the presence of limonoids. This is the first time extracts of the seeds were investigated. Previous work was done on the stem bark of this species. An andirobin-type limonoid, methyl angolensate (5), two mexicanolide-type limonoids, mexicanolide (6), khayasin (7), and three protolimonoids, sapelin E acetate (8), sapelin C (9) and grandifoliolenone (10), have been isolated in this work. One of these was novel. Cedrelopsis grevei belongs to the Cedrelopsis genus and has been classified into the Ptaeroxylaceae family. Extracts from the stem bark of Cedrelopsis grevei obtained from Madagascar yielded seven compounds, a triterpenoid, β-amyrin (15), a coumarin, scoparone (16), a limonoid, cedmiline (14), a triterpenoid derivative, cedashnine (17), a quassinoid, cedphiline (19), a lignan, cedpetine (18) as well as sitosteryl β-D-glucopyranoside (20). Three of these were novel. / Thesis (M.Sc.)-University of Natal, Durban, 2001.

No abstract available. / Thesis (M.Sc.)-University of Natal, Durban, 1991.

No abstract available. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.

No description available.