The kinetics and mechanism of permanganate oxidation of pyruvic acid in aqueous perchlorate at a constant ionic strength of 2.0 mol dm−3 have been investigated spectrophotometrically. The pseudo-first-order plots showed two distinct phases for the reaction, characterized as induction and auto-acceleration periods. The induction phase is relatively slow at the early stages of reaction and is followed by a faster process. The rate law for the oxidation was described by the sum of two exponential terms. The oxidation showed overall second-order kinetics with respect to the reactants in the initial slow phase. However, second-order kinetics was not maintained throughout the faster second stage. The effects of added salts lead to the conclusion that Mn(III) and/or Mn(IV) play the main role in the reaction kinetics of the second stage. A reaction mechanism consistent with the kinetic results is suggested and discussed.

The kinetics and mechanism of reduction of hexacyanoferrate (III) by biodegradable chondroitin-4-sulfate (CS) in alkaline solutions at a constant ionic strength of 1.0 mol dm−3 have been investigated spectrophotometrically. The kinetic results indicated that the reaction was first-order dependence in the oxidant and fractional-order kinetics with respect to the [CS]. The influence of the base on the oxidation rates indicates that the reaction was base-catalyzed. A kinetic evidence for formation of 1:1 intermediate complexeswas revealed. The kinetic parameters have been evaluated and a tentative reaction mechanismconsistentwith the kinetic results obtained is suggested and discussed.

The kinetics and mechanism of reduction of hexacyanoferrate (III) by biodegradable chondroitin-4-sulfate (CS) in alkaline solutions at a constant ionic strength of 1.0 mol dm−3 have been investigated spectrophotometrically. The kinetic results indicated that the reaction was first-order dependence in the oxidant and fractional-order kinetics with respect to the [CS]. The influence of the base on the oxidation rates indicates that the reaction was base-catalyzed. A kinetic evidence for formation of 1:1 intermediate complexeswas revealed. The kinetic parameters have been evaluated and a tentative reaction mechanismconsistentwith the kinetic results obtained is suggested and discussed.

Corrosion inhibition of aluminum (Al) in hydrochloric acid by anionic polyelectrolyte chondroitin-4-sulfate (CS) polysaccharide has been studied using both gasometrical and weight-loss techniques. The results drawn from these two techniques are comparable and exhibit negligible differences. The inhibition efficiency was found to increase with increasing the inhibitor concentration and decreased with increasing temperature. The inhibition action of CS on Al metal surface was found to obey both of Langmuir and Freundlich isotherms. The factors affecting the corrosion rates such as the concentration and geometrical structure of the inhibitor, concentration of the corrosive medium, and the temperature were examined. The kinetic parameters were evaluated and a suitable corrosion mechanism consistent with the results obtained is discussed.

Corrosion inhibition of aluminum (Al) in hydrochloric acid by anionic polyelectrolyte chondroitin-4-sulfate (CS) polysaccharide has been studied using both gasometrical and weight-loss techniques. The results drawn from these two techniques are comparable and exhibit negligible differences. The inhibition efficiency was found to increase with increasing the inhibitor concentration and decreased with increasing temperature. The inhibition action of CS on Al metal surface was found to obey both of Langmuir and Freundlich isotherms. The factors affecting the corrosion rates such as the concentration and geometrical structure of the inhibitor, concentration of the corrosive medium, and the temperature were examined. The kinetic parameters were evaluated and a suitable corrosion mechanism consistent with the results obtained is discussed.

Corrosion inhibition of aluminum (Al) in hydrochloric acid by anionic polyelectrolyte chondroitin-4-sulfate (CS) polysaccharide has been studied using both gasometrical and weight-loss techniques. The results drawn from these two techniques are comparable and exhibit negligible differences. The inhibition efficiency was found to increase with increasing the inhibitor concentration and decreased with increasing temperature. The inhibition action of CS on Al metal surface was found to obey both of Langmuir and Freundlich isotherms. The factors affecting the corrosion rates such as the concentration and geometrical structure of the inhibitor, concentration of the corrosive medium, and the temperature were examined. The kinetic parameters were evaluated and a suitable corrosion mechanism consistent with the results obtained is discussed.

Acarinina sibaiyaensis is a very distinctive and short-lived planktonic foraminiferal taxon that is restricted to the temporally short Carbon Isotope Excursion (CIE) interval characteristic of the Paleocene-Eocene Thermal Maximum (PETM) event. It is confined to the planktonic foraminiferal Zone E1 which in southern Egypt corresponds to the Dababiya Quarry Member (DQM). This member yields a complete record of the biotic changes induced by the intense warming during the basal Eocene. Although this distinctive taxon is widely distributed throughout the tropic to the temperate regions, its morphologic changes and phylogenetic relations during the CIE/PETM interval have not yet been documented. The present study discusses and documents the morphologic changes which affected the short-lived Ac. sibaiyaensis probably caused by the extreme warming during the very brief (175–200 ka) CIE/PETM interval in southern Egypt. These morphologic variations are particularly well developed in the middle phosphatic phase (Beds 2 and 3 of the DQM), in which the CIE curve shows its maximum negative shift. The origin, morphology, wall texture, coiling direction and their changes during ontogeny and evolution of Ac. sibaiyaensis during the CIE-PETM interval at Qreiya, Gebel Abu Had, northeast Qena (southern Nile Valley) and Darb Gaga (southeast of Kharga Oasis, southern Western Desert) are described, interpreted and illustrated. During the PETM, numerous intraspecific varieties of Ac. sibaiyaensis are recorded. Several evolutionary lineages are delineated; some of them stay within the morphologic range of Ac. sibaiyaensis, whereas others lead to other excursion taxa i.e. Acarinina africana and Morozovella allisonensis. In addition, forms transitional to taxa which appear in younger horizons than the PETM (younger than Zone E1) are recorded, described and illustrated.

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