Serious errors could be introduced into experimental results due to the observed non-additive nature of the count rate data
recorded by gamma scintillation counters, particularly when the samples are subjected to excessive dilution. Simple procedures
for correcting the experimental results are suggested.
Polyvalent ions are very sensitive to gamma irradiation in aqueous solutions. The present work is a part of a more comprehensive study dealing with the stabilization of certain oxidation states of some polyvalent ions during their gamma irradiation in aqueous systems. Sulphite ions, being well known reducing agents has been used for stabilizing Fe(II) ions in aqueous solutions during gamma radiolysis. Fe(II) ions in solution are known to be readily oxidized by gamma radiations in such a way that a 10–3N solution decays completely in about 2 hours at a dose rate 310 Gy/hr. In presence of an excess of sulphite ions it was found that Fe(II) ions were stabilized for extended time periods depending on the amount of sulphite ions used. The conditions of stabilization and its limits in the studied case has been identified.
The various aspects of valency stabilization of polyvalent ions during -radiolysis have been further investigated. Ce(IV) ions, which are normally reduced in their aqueous solution, were found to be stabilized for increasing periods of time when they were irradiated in the presence of increasing amounts of bromate ions. It was found that the addition of about fifteen times excess of bromate ions to a 10–3 N Ce(IV) solution stabilized the cerium ions in the tetravalent state for about 120 hours during irradiation at a dose rate of 336 Gy/h. Increasing the amount of bromate used resulted in a subsequent increase in the protection time. It has been also noted that while bromate ions protected Ce(IV) in solution, the latter ions showed a clear protective effect on the bromate used, i.e., there is a mutual protective effect. The probable mechanisms, conditions and limitations of the protection process have been discussed. Based on the data obtained in the present work, it has been suggested that the protection of Ce(IV) ions by bromate ions in aqueous solutions during -radiolysis is very probably due to the preferential interaction of bromate with the reducing radiolysis products of water which are capable of reducing Ce(IV) to Ce(III).
In the present work, the radiation-induced color bleaching of Remazol brilliant blue (RBB), Wegocet orange (WO), Methyl green
(Me G) and Thioflavine S (Th S) dyes solutions was studied. Solutions of these dyes in different solvents were found to obey
Beer’s law within certain concentration levels. The % color bleaching occurring in different dye solutions on using different
gamma irradiation doses was determined and the data obtained showed the existence of good linear relationships among them
in the four dye systems used. The linear sections lines were used as calibration curves for evaluating unknown gamma irradiation
doses. From the obtained results, it was concluded that RBB in water, WO in ethanol, Me G in butanol and Th S in 60% ethanol–water
mixture could be used for dose evaluation within the dose ranges 5–25 kGy for RBB, 20–90 kGy for WO, 10–70 kGy for Me G and
5–160 kGy for Th S. The sensitivity of the systems towards gamma radiations has been also reported.
The spectrophotometric determination of pure U(IV) or U(VI) ions in solution with Arsenazo I is greatly dependant on the pH of the solutions. The experimental conditions for the differential estimation of the different oxidation states of U ions, in the same sample, using Arsenazo I have been identified and implemented. The results showed that the applied method is rather rapid and accurate.
Simpson Violet dye has been exposed to γ-irradiation in non-aqueous solvents, and the color bleaching by irradiation was studied. The color bleaching was related to the applied dose. In another series of experiments, Simpson Violet dye was incorporated in polymethylmethacrylate films for studying the dose-response relationship. Finally, the results were compared with those obtained for externally dyed polymeric films. Most of the systems investigated were found suitable for gamma dose evaluation within a certain dose range.
Authors:A. Bahgat, M. Ahmed, A. Barakat, and T. Ramadan
A stone of brick-like shape, measuring roughly 25×12.5×10.5 cm3 and weighing 14 kg was found in 1983, in the western desert of Egypt. The meteorite was named El-Bahrain meteorite and classified as L-chondrite. In the present paper, the principal constituents of El-Bahrain meteorite have been studied by means of Mössbauer spectroscopy. The chemical composition as obtained by the conventional wet analyses of L-chondritic meteorites showed that the meteorite contains 23.38% Fe and 1.23% Ni. While the analysis of the atomic absorption showed the presence of 27.03% as a total iron. The Mössbauer analysis of El-Bahrain meteorite showed that the iron constituent minerals were determined to be olivine, metallic iron-nickel alloys (kamacite, taenite and tetrataenite), ferrous sulfide (troilite) and weathering products such as maghemite and nanocrystalline hematite. The structure of meteoritic iron obtained by the Mössbauer analysis has been discussed on the basis of these constituents.
Authors:M. A. Henaish, S. A. Olofa, M. M. Barakat, and T. Tawfik
A series of samples in the system Ni0.65Zn0.35CuxFe2−xO4 (x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) were prepared by the usual ceramic technique. Seebeck coefficient, d.c. resistivity, activation energy, drift mobilityΜ and time constant measurements are presented for all samples. As expected, the activation energies were lower for samples of higher conductivity and mobility.