Spectrophotometric Studies of the Behaviour of Multidentate Schiff Base Ligands with Copper(II) in Methanol Solution

Four formation reaction complexes of polydentate Schiff base ligands derived from condensation of ethylenediamine with salicylaldehyde (L1) and 2-pyridinecarboxaldehyde (L2) and of diethylenetriamine with salicylaldehyde (L3) and 2-hydroxy-1-naphthaldehyde (L4) as electron donors with copper (II) chloride as an electron acceptor in methanol were studied spectrophotometrically at 301 K. The absorption band wavelengths of the electron donors, the electron acceptor and their complexes were measured and studied. Parameters such as the molar absorptivities, eAD, of these complexes and the equilibrium constants, KAD, of their formation reactions obtained from the Benesi-Hildebrand equation were established and discussed. The absorption band energies of the complexes, E, the ionization potentials of the Schiff base ligands, ID, and the Gibbs energy changes of the above reactions, ΔG, were calculated. Finally, kinetic parameters such as the orders of the reactions, and the rate constants of the forward and reverse reactions, k1 and k-1, were determined. Key Words: UV-Visible,Spectrophotometry,Schiff base ligand,Transition metal complexes,Copper(II) chloride,Methanol,Benesi-Hildebrand South African Journal of Chemistry Vol.57 2004: 33-3

Le maintien du cours légal du billet de la Banque de France auprès des Caisses publiques (1850-1870): Interprétation d'une décision "hétérodoxe".

The unorthodox decision taken in 1850 to oblige the Treasury Offices to accept the bank notes of the Bank of France, in spite of the repeal of the forced currency in 1848, or in other words the maintaining of the legal tender of the note in relation to the Treasury Offices (Introduction), would be understandable with the following hypothesis. This unorthodox decision would indirectly come down to recovery the tax in cash by the Bank of France (I-1), and would make possible to the Bank of France, thanks to the income of the tax, to stabilize its reserve that is structurally unstable (I-2), even if it must be necessary to raise the bank rate in the event of important withdrawals realized by the Treasury (I-3). In this way, the Bank of France would finance in cash, thanks to this aid from the State, the needs of the economy (II-2), while the maintaining of the legal tender in relation to the Treasury Offices, would make possible to finance the public Deficit exclusively with its notes (II-1). This monetary policy carried out by the Bank of France in 1850, would have taken as pattern, the monetary policy fulfilled by the Bank of England, through the 1844 's Banking Charter Act of Peel (II-3).La décision "hétérodoxe" prise en 1850 d'obliger les Receveurs généraux à recevoir le billet de la Banque de France, malgré l'abrogation du cours forcé, autrement dit le maintien "hétérodoxe" du cours légal du billet de la BF auprès des Caisses publiques (Introduction), s'expliquerait par l'hypothèse suivante: cette décision "hétérodoxe" se ramènerait indirectement à un recouvrement en espèces de l'impot par la BF (I-1) et permettrait alors à la BF de stabiliser son Encaisse, structurellement aléatoire, grace au produit de la fiscalité (I-2), quitte à élever le taux de l'escompte en cas de retraits significatifs opérés par le Trésor (I-3). La BF financerait alors en espèces grace à cette aide de l'Etat, le crédit à l'écnomie (II-2), alors que le maintien du cours légal auprès des Caisses publiques, lui aurait permis de financer le déficit public par "création monétaire" (II-1). Cette politique monétaire mise en oeuvre par la BF dès 1850, aurait pris comme modèle celle mise en oeuvre en 1844 par la Banque d'Angleterre, sous le nom d'Act de Peel

Comparison of dielectric properties of olive oil, mineral oil, and other natural and synthetic ester liquids under AC and lightning impulse stresses

International audienceThis paper presents experimental results of a comparative study of the characteristics of streamers propagating in olive oil and breakdown voltage with mineral oil, rapeseed oil (natural ester) and tetra-ester and methyl oleate (synthetic ester liquids). The comparison focuses more particularly on the pattern, stopping length, associated current and electrical charge of streamers propagating in a point-plane electrodes geometry under (1.2/50 μs) lightning impulse (LI) voltage as well as breakdown voltages under AC and LI voltages. A statistical analysis of breakdown voltages is also achieved. It is shown that the streamer characteristics (streamers shape, stopping length, associated current and electrical charge) of olive oil in small gaps are comparable to those of mineral oil. Breakdown voltages under AC and LI voltages are found to be higher in olive oil than in mineral oil. Consequently, olive oil can constitute a potential substitute for mineral oil in in high voltage power transformers

Creeping discharges propagating on natural ester oils/pressboard interface under AC and lightning impulse voltages

International audienceThis paper presents the results of experimental characterization of creeping discharges propagating over pressboard immersed in insulating oils, under AC and standard lightning impulse voltages. For comparison purposes, synthetic ester, rape seeds oil (natural ester) and mineral oil were also investigated. Two experimental arrangements were used: (1) a point-to-plane electrodes system where the pressboard is inserted between the electrodes such as the point is perpendicular to pressboard allowing a radial propagation of discharges; and (2) a point-to-bar electrodes system allowing a propagation of discharges in one direction, tangentially to pressboard. The characteristics of discharges propagation, their shape, stopping length (the maximum extension of creeping discharge) as well as the associated current and electrical charge versus the thickness of pressboard and the type of oil are analyzed. It is shown that the magnitude and polarity of voltage, the type of oil as well as the thickness of pressboard influence the characteristics of discharges and especially the stopping length and density of branches. The stopping length of creeping discharges is shorter for pressboard/naturel esters' interfaces than with pressboard/mineral oil interface

Comparison of creeping discharges propagating over pressboard immersed in olive oil, mineral oil and other natural and synthetic ester liquids under DC voltage

International audienceThis paper presents an experimental study on the characteristics of creeping discharges propagating over pressboard immersed in olive oil, rapeseed oil, tetra-ester, methyl oleate, and mineral oil, under both negative and positive DC voltages. The investigated characteristics are mainly the shape of discharges and their stopping lengths. Two experimental test cells are used: in the first one, the pressboard is inserted between pointe and plane electrodes so that the tip is perpendicular and at the center of the pressboard sample; and in the second one, the pressboard is placed between a point and bar electrodes in a way that allow a propagation in one direction (tangentially to pressboard). It is observed that the creeping discharges under DC voltage are not radial. Their shapes are different from those observed in previous work under AC and lightning impulse voltages. On the other hand, for given voltage and pressboard thickness, the stopping length L f is shorter when the point is negative than when it is positive indicating that the flashover voltage will be greater with a negative point This also evidences a difference in the processes involved in each polarity especially the space charge resulting of the injected charges and the charge accumulated at the interface (including the charges resulting of double layer) as well as the evolution of the electric field in the vicinity of the point electrode and along the pressboard surface. For a given pressboard thickness, L f increases with the voltage; it decreases when the thickness of pressboard is reduced