I. M. Issa

Reduction of azo-compounds—I. Polarographic behaviour of some 4-hydroxymonoazo compounds at the dropping mercury electrode

Abstract The polarographic behaviour of some monoazo compounds has been studied in aqueous solutions of varying pH. The reduction current in alkaline media is almost half that of the limiting value in acid solution, indicating a change in the mechanism of reduction. A general mechanism for the reduction process in alkaline and acid media is suggested, which includes a rate-determining step involving one electron. The different kinetic parameters for the electrode reaction support the suggested mechanism. The effect of substituents is clarified.

The polarographic behaviour of cystine in solutions of varying pH at the dropping mercury electrode and effect of surface-active substances☆

The polarographic behaviour of cystine in solutions of varying pH was studied within the concentration range 0·06–1·3 mM at the dme. The polarograms each consist of a single wave in acid solutions of pH < 2 and two waves at higher pH, the first of which is apparently smaller than the second. Analysis of the waves proved that the first wave is less irreversible and exhibits a kinetic contribution whereas the second is irreversible and controlled by diffusion. The effect of pH on the limiting current and E12 as well as the reduction mechanism are discussed. The kinetic parameters are also determined in the absence and the presence of surface-active materials.

Kinetics of reduction of hexavalent uranium in sulphuric acid solutions. A simplified method for determining the parameters of irreversible waves

Abstract The polarographic behaviour of U(VI) has been studied in sulphuric acid solutions of different concentrations and the different kinetic parameters are determined. The nature of the polarograms differs in accordance with the acid concentration. The diffusion coefficient of U(VI) is found to be 3·51 × 10 −6 , 6·02 × 10 −6 and 6·52 × 10 −6 cm 2 /s for 5·0, 1·0 and 0·1 M H 2 SO 4 respectively. The waves being irreversible are analysed by the Koutecky—Delahay treatments and also by a proposed simpler procedure; the latter proved to be more easy and rapid. The values of the different kinetic parameters reveals that the irreversibility of the electrode reaction decreases with rise of sulphuric acid concentration.

Polarography of eosin and erythrosin in solutions of varying pH at the DME

Abstract The polarographic behaviour of eosin and erythrosin in buffer solutions of pH 4–11 is discussed. The observed waves are assigned to the reduction of furan and pyrone rings of the molecule of erythrosin at pH 4–11 and for eosin at pH ⩽7. The nature of the waves is also investigated. In alkaline media the electrode reaction is essentially diffusion controlled whereas at pH

The polarographic behaviour of Mn(III) in fluoride solutions and in the presence of surfactants

The polarographic behaviour of tervalent manganese in 0·08 M NaF was studied both in the absence and in the presence of surface-active substances. The polarograms of Mn(III) in the absence of surfactants began to show a maximum at concentrations higher than 5·7 × 10−4 M Mn(III). A plot of idvs the concentration of Mn(III) gave a linear relationship, indicating the validity of the Ilkovic equation. In the presence of surfactants such as Triton X-100 and sodium dodecylbenzene sulphonate, the wave was highly distorted, while the effect of dodecylamine perchlorate was insignificant. The influence of mercury height on the limiting current shows that the process of reduction is mainly diffusion-controlled, although from evaluation of the kinetic parameters, it appears to be partially kinetically controlled. The plot of E vs log i/(id - i) for the shifted wave shows that the process is irreversible and involves the uptake of one electron. It is proposed that reduction takes place according to MnF4− + 2 H+ + e → Mn2+ + 2 HF2−.

Polarography of dihalogen fluoresceins in solutions of varying pH at the dme

Abstract The polarographic behaviour of dichloro-, dibromo- and di-iodofluorescein has been studied in buffer solutions (pH 4–12) at the dme. The reduction of dichloro- and dibromo-derivatives involves the uptake of two electrons whereby the furane ring is reduced. At low pH (⩽7) a small wave appears, which is attributed to the partial reduction of the pyrone ring. In the case of diiodofluorescein, four electrons are consumed, corresponding to the reduction of both furane and pyrone rings at all pHs. The nature of the reduction waves is discussed.

Die Reaktion von Ce(III), Th(IV) und U(VI) mit Chinizaringrün und seinem nichtsulfonierten Grundkörper

The reaction of 1,4-(2′-sulpho-4′-methylanilino)anthraquinone (quinizarin green,QG) and its non-sulphonated derivative (NSQG) with Ce(III), Th(IV), and U(VI) was investigated. Spectrophotometric and conductometric studies were carried out to investigate the stoichiometry of the complexes formed. The studies revealed the formation of 1∶1 and 1∶2 (M∶L) complexes. The apparent stability constants of the different complexes were determined. The structure of the ligand in the solid chelates was studied by IR spectrophotometry which showed that the chelate formation takes place through the oxygen of the C=O group and the α-imino nitrogen.

Indium(III) complexes with some salicylidene aromaticSchiff bases

In(III) complexes with salicylidene aromaticSchiff bases have been prepared. The nature of the complexes has been studied by microanalysis of the solid complexes, conductometric titration, uv and ir spectrophotometric measurements. The complexes are of the type 1∶1 and 2∶1 [Ligand: In(III)] depending upon theSchiff base. The tendency of the salicylideneSchiff base molecule towards complex formation with In(III) is found to depend largely on the strength of the intramolecular hydrogen bond established between the aldehydic OH group and C=N. Furthermore, it is concluded that theseSchiff bases cordinate to In(III) as tri- or bidentate ligands depending upon the molecular structure of theSchiff base (not as monodentate ligand as previously described). The high molar absorbance of the 1∶2 In(III) complex with salicylidene-o-hydroxyaniline I (17,800 mol−1 cm2) can be applied for the micro determination of small amounts of Indium as low as 0.57 μg/ml solution.ZusammenfassungEs wurden einige In(III)-Komplexe mit (von Salicylaldehyd hergeleiteten)Schiff-Basen hergestellt. Elementaranalyse, konduktometrische Titration und UV- sowie IR-Spektroskopie wurden zur Aufklärung der Komplexe herangezogen. Es werden je nach verwendeterSchiff-Base 1∶1-oder 2∶1-Komplexe gebildet. Die Bildungstendenz der Komplexe mit denSchiff-Basen als drei- oder zweizähnige Liganden hängt weitgehend von Stärke und Ausbildungsmöglichkeit von H-Brückenbindungen ab. Einer der beschriebenen Komplexe ist zur photometrischen Mikrobestimmung von In(III) geeignet.

Studies on the reaction of salicylidenebenzoic-hydrazide (SBH) with Ce3+, Th4+ and UO22+

The stoichiometry and structure of salicylidenebenzoic-hydrazine (SBH) chelates with UO2(II), Ce(III) and Th(IV) in buffer-ethanol mixtures and in pure ethanol is studied applying conductometric titration, visible spectrophotometry and ir-spectrophotometry. The ir-spectra revealed that coordination takes place through the C=O and C=N groups.ZusammenfassungDie Stöchiometrie und die Struktur derSBH-Me(x) Chelate in Puffer-Ethanol-Mischungen und in reinem Ethanol wurde mittels Leitfähigkeitsmessungen, UV- und IR-Spektroskopie untersucht. Insbesondere die IR-Messungen zeigen, daß die Koordination über die C=O- und C=N-Gruppierung stattfindet.The stoichiometry and structure of salicylidenebenzoic-hydrazine (SBH) chelates with UO2(II), Ce(III) and Th(IV) in buffer-ethanol mixtures and in pure ethanol is studied applying conductometric titration, visible spectrophotometry and ir-spectrophotometry. The ir-spectra revealed that coordination takes place through the C=O and C=N groups.

Thorium[IV], Uranium[VI] and Ce[III] complexes with bidentate and tridentate Schiff bases

Thorium(IV), Uranium(VI) and Cerium(III) complexes with some bidentate and tridentateSchiff bases-derived from salicyladehyde-have been prepared. The effect of the molecular structure of theSchiff base molecule on its tendency towards complex formation has been studied. The structures of the complexes have been investigated by elemental analysis, molar ratio and continuous variation spectrophotometric methods, infrared spectra and conductometric titrations; the apparent formation constants have been determined as well.ZusammenfassungEs wurden Thorium(IV)-, Uran(VI)- und Cer(III)-Komplexe einiger zwei-und dreizähnigerSchiff-Basen (hergeleitet vom Salicylaldehyd) dargestellt, um den Einfluß der Molekülstruktur derSchiff-Base auf das Komplexierungsvermögen zu studieren. Die Struktur der Komplexe wurde mittels Elementaranalyse, elektronenspektrometrischer Methoden, IR-Spektrometrie und Leitfähigkeitsmessungen untersucht. Die Komplexbildungskonstanten wurden gleich-falls bestimmt.