African Journals Online
Bulletin of The Chemical Society of Ethiopia

Volume 15, Number 1, June 2001
Abstracts

ELECTROCHEMICAL BEHAVIOUR OF GOLD AT THE CARBON PASTE ELECTRODE: APPLICATION TO THE GOLD ORE ANALYSIS

M. Diaw¹*, D. Lemordant², O. Sock¹ and O. Sarr<sup>3

1</sup>Laboratoire d'Electrochimie et des Procédés Membranaires, Ecole Supérieure Polytechnique, BP 5085 Dakar-Fann, Université Cheikh Anta Diop, Dakar, Senegal
²Laboratoire de Physicochimie des Interfaces et des Milieux Réactionnels, EA2098, Université de Tours, Faculté des Sciences, Parc Grandmont, 37200 Tours, France
³Laboratoire de Chimie Minérale et Analytique, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Senegal

(Received December 5, 2000; revised March 22, 2001)

ABSTRACT. Electroanalysis of gold and gold derivatives incorporated in a carbon paste electrode has been shown to be a useful tool for gold speciation. This technique allows a rapid access to the oxidation state of gold in the composite under study. Voltammetric studies have been conducted on metallic gold, gold oxide and gold(III) solutions in hydrochloric and sulphuric acids. Moreover the analysis of a gold ore has been performed in order to investigate the possibility of determining the presence of gold in pyrite gangue. 


APPLICATION OF COPPER(II) CATALYSIS OF THE OXIDATION OF 2-HYDRAZINO PYRIDINE BY HYDROGEN PEROXIDE: A KINETIC METHOD OF ANALYSIS

F.A. Sunday Fabiyi¹*, George O. Adediran¹ and M. Adegboyega Olatunji<sup>2

1</sup>Department of Chemistry, Faculty of Science, University of Ilorin, Kwara State, Nigeria
²Department of Chemistry, School of Science, Federal University of Technology, Minna, 
Niger State, Nigeria

(Received May 4, 2000; revised January 28, 2001)

ABSTRACT. A sensitive kinetic method of analysis for the determination of trace amounts of Cu2+ ion has been developed. The method is based on the catalytic effect of Cu2+ ion on the oxidation of 2-hydrazino pyridine. The oxidation product coupled with m-phenylenediamine formed a yellow azo dye. The reaction was followed spectrophotometrically at lmax = 454 nm and at a fixed temperature of 35 0C. A fixed time of 11 min was chosen for the quantitative determination of copper(II). Among the ions tested for interference, only Mn2+ and Fe2+ ions interfered seriously when present in excess of 10 and 8 mgmL-1, respectively. The method was applied to the determination of copper in some carbonated drinks marketed in Nigeria. The results compared satisfactorily with that of atomic absorption spectrometry. The method is sensitive to Cu2+ ion determination in the concentration range of 0.05-1.5 mgmL-1.


SYNTHESIS AND STRUCTURAL INVESTIGATIONS OF  DIOXOURANIUM(VI) COORDINATION COMPOUNDS OF 4-[N-(p-DIMETHYLAMINOBENZALIDENE)AMINO] ANTIPYRINE THIOSEMICARBAZONE†

Ram K. Agarwal¹* and Himanshu Agarwal<sup>2

1</sup>Department of Chemistry, Lajpat Rai Post-Graduate College, Sahibabad-201 005, Ghaziabad, India; ²Department of Applied Chemistry and Polymer Technology, Delhi College of Engineering, New Campus, Bawana Road, Delhi-110 042, India

(Received August 31, 2000; revised January 15, 2001)

ABSTRACT. This paper reports the isolation of some solid coordination compounds of dioxouranium(VI) with a 4-[N-(p-dimethylaminobenzalidene)amino]antipyrine thiosemicarbazone (DABAAPT). The analytical data indicate that the complexes have the general composition UO2X2.n(DABAAPT) (X = Br-, I-, NCS- or ClO4-, n = 2; X = NO3- or CH3COO-, n = 1). These compounds were characterized by various physico-chemical techniques. The ligand behaves as tridentate N,N,S-donor. The probable coordination number of uranium is found to be 8, 9 or 10 depending on the nature of anionic ligand. Wilson's G-F matrix method was used to determine the stretching and interaction force-constants from which the U-O bond distances were calculated. Thermal stabilities of these compounds were also investigated.


THE PHOSPHINE-EXCHANGE REACTION WITH AN EQUIMOLAR MIXTURE OF [(h5-C5H5)Fe(CO)2PPh3]+[PF6]- AND P(2-C4H3O)3 (C4H3O = FURANYL)

O.G. Adeyemi^{1, 2} * and L.-K.Liu2, <sup>3

1</sup>Department of Chemistry, University of Ilorin, Ilorin, Nigeria; 
²Institute of Chemistry, Academia Sinica, Taipei, Taiwan, ROC
³Department of Chemistry, National Taiwan University, Taipei, Taiwan, ROC

(Received August 11, 2000; revised January 17, 2001)

ABSTRACT. A trace amount of n-BuLi at -78 oC initiates a chemical attack on [(h5-C5H5)Fe(CO)2I] by the ligands (PPh3 and P(2-C4H3O)3) leading to the formation of cationic species, [(h5-C5H5)Fe(CO)2PPh3]+[I]- and [(h5-C5H5)Fe(CO)2P(2-C4H3O)3)]+[I]-. Anion exchange could be conveniently carried out by dissolving the iodides in a solutions of excess NH4PF6 in CH3CN, to afford yellow solids [(h5-C5H5)Fe(CO)2PPh3]+[PF6]- and [(h5-C5H5)Fe(CO)2P(2-C4H3O)3)]+[PF6]-. The determination of the equilibrium constant K was carried out in a single experiment in an NMR tube, utilizing MeLi as reductant in the phosphine exchange reaction. The slight difference in donor capability of the two ligands (PPh3 and P(2-C4H3O)3) was observed as supporting evidence for their stereo-electronic properties.

STUDIES OF TRANSITION METAL COMPLEXES OF HERBICIDAL COMPOUNDS. I: TRANSITION METAL COMPLEXES OF 2-METHYLTHIO-4-AZIDO-6-ISOPROPYLAMINO-S-TRIAZINE (AZIPROTRYN)

Worku Dinku¹, Negussie Megersa1, V.J.T. Raju1,², Theodros Solomon¹, Jan Åke Jönsson³ and Negussie Retta¹*

¹Department of Chemistry, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia
²Department of Chemistry, Osmania University, Hyderabad 500 007, India
³Department of Analytical Chemistry, Lund University, Box 124, S-221 00 Lund, Sweden

(Received December 25, 2000; revised March 1, 2001)

ABSTRACT. Divalent cobalt, nickel, copper and zinc complexes of herbicidally ac