The acid-catalysis of chromic acid oxidation of carboxymethyl cellulose (CMC) as a polysaccharide in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm−3 have been investigated spectrophotometrically. The experimental results showed first-order kinetics in chromic acid and fractional first-order dependence with respect to [CMC]. A kinetic evidence for the formation of 1:1 complex between chromic acid and CMC was revealed. The hydrogen ion dependence of the reaction rates showed that the oxidation process is acid-catalyzed. Induced polymerization of acrylonitrile indicated that the oxidation process proceeds by free-radical mechanism. The kinetic parameters have been evaluated and a tentative reaction mechanism consistent with the kinetic results is suggested.

The acid-catalysis of chromic acid oxidation of carboxymethyl cellulose (CMC) as a polysaccharide in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm−3 have been investigated spectrophotometrically. The experimental results showed first-order kinetics in chromic acid and fractional first-order dependence with respect to [CMC]. A kinetic evidence for the formation of 1:1 complex between chromic acid and CMC was revealed. The hydrogen ion dependence of the reaction rates showed that the oxidation process is acid-catalyzed. Induced polymerization of acrylonitrile indicated that the oxidation process proceeds by free-radical mechanism. The kinetic parameters have been evaluated and a tentative reaction mechanism consistent with the kinetic results is suggested.

The acid-catalysis of chromic acid oxidation of carboxymethyl cellulose (CMC) as a polysaccharide in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm−3 have been investigated spectrophotometrically. The experimental results showed first-order kinetics in chromic acid and fractional first-order dependence with respect to [CMC]. A kinetic evidence for the formation of 1:1 complex between chromic acid and CMC was revealed. The hydrogen ion dependence of the reaction rates showed that the oxidation process is acid-catalyzed. Induced polymerization of acrylonitrile indicated that the oxidation process proceeds by free-radical mechanism. The kinetic parameters have been evaluated and a tentative reaction mechanism consistent with the kinetic results is suggested.

The acid-catalysis of chromic acid oxidation of carboxymethyl cellulose (CMC) as a polysaccharide in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm−3 have been investigated spectrophotometrically. The experimental results showed first-order kinetics in chromic acid and fractional first-order dependence with respect to [CMC]. A kinetic evidence for the formation of 1:1 complex between chromic acid and CMC was revealed. The hydrogen ion dependence of the reaction rates showed that the oxidation process is acid-catalyzed. Induced polymerization of acrylonitrile indicated that the oxidation process proceeds by free-radical mechanism. The kinetic parameters have been evaluated and a tentative reaction mechanism consistent with the kinetic results is suggested.

The oxidative status and the morphological changes of liver of rats exposed to cadmium (5 mg Cd/kg body weight subcutaneously) for 22 days and the protective role of melatonin (10 mg/kg b.w.) against the toxicity of cadmium was studied. The concentration of malondialdehyde (MDA), as an indicator of lipid peroxidation, activity of the antioxidant enzyme superoxide dismutase (SOD) as well as the concentration of glutathione (GSH) was measured in the liver. The morphological changes were investigated using both light and electron microscopes. The exposure to Cd led to an increase of MDA levels and a decrease of both the activity of SOD and GSH concentration in the liver. In contrast, melatonin administration restored the previous changes to nearly the normal levels. Morphologically, Cd led to different histopathological changes such as loss of normal architecture of the parenchymatous tissue, cytoplasmic vacuolization, cellular degeneration and necrosis, congested blood vessels, destructed cristae mitochondria, fat globules, severe glycogen depletion, lipofuscin pigments, and collagenous fibers formation. Again, melatonin administration counteracts all changes and the tissue appears more or less normal. The rate of recovery was faster when melatonin was administered for treatment after the exposure to cadmium than if the animals left without any treatment. The results suggest that melatonin may be useful as an antioxidant in combating free radical-induced oxidative stress and tissue injury that is a result of cadmium toxicity.

The oxidative status and the morphological changes of liver of rats exposed to cadmium (5 mg Cd/kg body weight subcutaneously) for 22 days and the protective role of melatonin (10 mg/kg b.w.) against the toxicity of cadmium was studied. The concentration of malondialdehyde (MDA), as an indicator of lipid peroxidation, activity of the antioxidant enzyme superoxide dismutase (SOD) as well as the concentration of glutathione (GSH) was measured in the liver. The morphological changes were investigated using both light and electron microscopes. The exposure to Cd led to an increase of MDA levels and a decrease of both the activity of SOD and GSH concentration in the liver. In contrast, melatonin administration restored the previous changes to nearly the normal levels. Morphologically, Cd led to different histopathological changes such as loss of normal architecture of the parenchymatous tissue, cytoplasmic vacuolization, cellular degeneration and necrosis, congested blood vessels, destructed cristae mitochondria, fat globules, severe glycogen depletion, lipofuscin pigments, and collagenous fibers formation. Again, melatonin administration counteracts all changes and the tissue appears more or less normal. The rate of recovery was faster when melatonin was administered for treatment after the exposure to cadmium than if the animals left without any treatment. The results suggest that melatonin may be useful as an antioxidant in combating free radical-induced oxidative stress and tissue injury that is a result of cadmium toxicity.

The influence of Rb in the triple sulfate LiK(1−x)RbxSO4 (0 ≤ x ≤ 0.2) compound on the structural and thermal properties of the bulk material is discussed. Samples were prepared by fusing the sulfates in stoichiometric ratios in a platinum crucible at 1273 K for 30 min. The x-ray powder diffraction measurements were performed at ambient temperature. The crystal structure parameters were refined by the Rietveld method using the FullProf program. The analysis indicated a single-phase having a hexagonal symmetry with space group P63 regardless of the Rb content. Thermal analysis by differential scanning calorimetry shows a considerable shift of the phase transition point towards lower temperatures with increasing Rb content. A pre-transitional effect is observed by differential thermal analysis of the sample without Rb contribution while for the sample with 20% Rb the transition is represented by double endothermic peaks. The energy of transition has been estimated using the Kissinger method for samples with different concentrations of Rb