Volume 5, Issue 3

The isotopic exchange reaction between 1-iodo-2,4-dinitronaphthalene and potassium iodide has been followed in acetone solution using iodine-131 as tracer, at various temperatures and over a wide range of concentration of iodide ion. To separate the organic from the inorganic compound a toluene-water extraction method was applied and to follow the increasing activity of the organic compound, a liquid scintillator technique has been adopted. Specific rates and the Arrhenius parameters have been calculated.

Zusammenfassung Der 36 Cl- bzw. 82 Br-Isotopenaustausch zwischen kovalent- und ionisch-gebundenen Halogenatomen wurde in kristallinem c is- und trans-[Co(en) 2 Cl 2 ] Cl und trans- [Co(en) 2 Br 2 ] Br zwischen 100 und 170 °C untersucht, sowie im trans-[Rh(en) 2 Cl 2 ]Cl zwischen 170 und 300 °C. Die Aktivierungsenergien dieser Austauschreaktionen wurden zu 30-34 kcal/mol ermittelt. Durch eine Vorbestrahlung mit Röntgen- oder 60 Co-γ-Strahlen steigt die Geschwindigkeit des Isotopenaustausches im festen trans -[Co(en) 2 Cl 2 ]Cl mit der Dosis stark an. Röntgenbremsstrahlung ist wirksamer als 60 Co-γ-Strahlen. Der Austausch dürfte nach einem Sprungmechanismus an Fehlstellen im Gitter erfolgen.

Zusammenfassung Die Austauschadsorption von Cs- und Sr-Ionen an reinstem Titandioxidhydrat wird untersucht. Die Herstellung des TiO 2 · aq erfolgt durch Hydrolyse von Orthotitansäuretetraäthylester. Bei der Bestimmung der Austauschkapazität des TiO 2 · aq durch Titration mit CsOH oder Sr(OH) 2 werden je nach den Versuchsbedingungen ein, zwei oder drei Wendepunkte erhalten, die den Kapazitäten 0,1, 0,2 und 0,3 g-Atom Metallion pro Mol TiO 2 · aq entsprechen. Aus trägerfreien Radionuklidlösungen wird Sr bei jedem p H -Wert zwischen 5 und 12 stärker adsorbiert als Cs. Die Cs-Adsorption wird durch Anwesenheit anderer einwertiger Kationen zurückgedrängt. Dabei verhalten sich die Ionenaktivitäten, die die Cs- Adsorption in gleichem Maße beeinflussen, wie Cs : Κ : Na : Li : N(CH 3 ) 4 = 1 : 2,2 : 12,5 : 37 : 490. Die Adsorption von Cs kann quantitativ als Cs-H-Austausch beschrieben werden. Sr wird offenbar teilweise als einwertiges und teilweise als zweiwertiges Ion eingetauscht. Unter dieser Voraussetzung kann auch die Sr-Adsorption als Sr-H-Austausch gedeutet werden. Bei konstantem p H -Wert kann die Austauschadsorption an TiO 2 ・ aq durch die Langmuir’sche Adsorptionsisotherme beschrieben werden.

A simple method is presented for the preparation of alpha sources to be analyzed by an alpha spectrometer equipped with a semi-conductor detector. The procedure consists of evaporating to dryness an aqueous solution of the alpha-emitter, redissolving the residue in situ with 0.1 Ν HNO 3 , precipitating with 3 Ν NH 4 OH and drying. The residual NH 4 NO 3 is redissolved in 3 N NH 4 OH, dried again, and sublimed at a higher temperature. The deposit is washed with distilled water, after which the plate is dried and ignited at red heat. Dramatic improvement is illustrated with several alpha emitters of different chemical properties, including 208/209 Po, 230 Th, 231 Pa, 232/234 U, and 238/239 Pu. By providing better distribution of the alpha-emitting nuclides and by removing alpha-absorbing impurities, the same procedure significantly increases the gross alpha counting rate and is recommended for use in improving the accuracy and reproducibility of routine alpha counting.

Zusammenfassung Es wird eine Proportionalzählrohr-Meßmethode beschrieben, die eine gleichzeitige Bestimmung der Radioaktivitäten von 3 H und 14 C ermöglicht.

Red crystalline selenium was irradiated with neutrons and the distribution of radioactive selenium between the red and grey allotropic modifications was investigated. Approximately 2 per cent of activity was stabilized in the grey modification with an enrichment of about ten, which decreased during thermal annealing.

52 Ti was produced in a reactor by neutron irradiation of Li 2 TiF 6 . Lithium enriched in 6 Li was used to prepare the compound. The half-life is 49 ± 3 min. The mass number could be established by identification of 52 V as the daughter product. The half-life was confirmed by periodic milking of 52 V. Chemical procedures used for the preparation of Li 2 TiF 6 , the purification of 52 Ti and the milking of 52 V are described.

The possibility of different behaviours of 60 Co and 60m Co in the Szilard-Chalmers recoil was investigated and proved in [Co(NH) 3 ) 6 ] (NO 3 ) 3 and trans - [Co en 2 (NO 2 ) 2 ] NO 3 . It was found that the retentions of 60 Co and 60m Co atoms in the original compounds, for irradiation time approaching zero, are different. Particularly the ratio of i0B,Co to eoCo retentions at zero irradiation time is 0.90 + 0.02 for [Co(NH 3 ) 5 ] . (NO 3 ) 3 and 1.26 + 0.04 for trans - [Co en 2 (NO 2 )] NO 3 . The annealing kinetics of recoiled 60 Co and 60m Co atoms under fast neutron and γ-ray irradiations at a temperature of 40 °C are also different.

A method is described by means of which the chemical effects of 81 Br (n, γ) 82m Br and 82m Br IT →82Br in n-propyl bromide can be determined separately. In the latter case effects due to the decay of n•C 3 H 7 - 82m Br and to the decay of inorganic 82m Br can also be separated, not only in the pure system but also in solutions of n-propyl bromide in methyl alcohol containing Br- . The results obtained show that (n, γ ) activation produces much lower organic retention than activation by isomeric transition. Moreover the organic yield of 82Bris much higher when it is born from n-C 3 H 7 - 82m Br than when it is born from inorganic 82m Br. These are explained by assuming that the probability of recombination of 82 Br with the parent radical, after bond rupture, is very high in isomeric transition activation but lower in (n, γ ) activation, owing probably to the different recoil energies of the two processes. Retentions as parent compound are high and their ratio to total organic yield is constant in all cases. The half-life of 82m Br has been determined through its chemical effects but this shows a small variation with change in temperature.

The reactions of recoiling carbon atoms produced via the 14 N (p, α ) 11 C process have been studied in gaseous and liquid methylamine, with and without scavenger. The product forming mechanisms in this system seem to follow the general pattern of the chemistry of energetic carbon atoms in simple hydrocarbons. The major products resulting from fragmentation of excited intermediates are acetylene and ethylene. As expected ethylamine and dimethylamine are found as the synthesis products. A small yield of acetonitrile, which remains unaffected by the presence of scavenger or the change of phase, is also found. In agreement with the deexcitation-fragmentation hypothesis the yield of the fragmentation products acetylene and ethylene decreases while the yield of the synthesis products ethylamine and dimethylamine increases in the condensed phases. The formation of the products is explained on the basis of insertion reactions. From comparison of the acetylene and ethylene yields in methylamine with those in the ethane system it seems that C-Η bonds are much more reactive towards insertion reactions than N-H bonds. Whether this is due to a lower reaction probability or to a more easily stabilized intermediate cannot be decided on the basis of the present evidence. Furthermore, the comparison with alkane systems shows no effect of the "leaving group" on the postulated acetylene and ethylene producing fragmentation process. It is suggested that the formation of acetonitrile takes place via decomposition of an excited ethyleneimine molecule, since the activity is equally distributed between the two carbon atoms.

The ambient atmosphere is found to influence the thermal annealing behaviour of neutron-irradiated bissalicylaldehyde- triethylenetetramine Co(III) chloride, hydrate. The electron-donors, acetone and ethyl alcohol vapours, accelerate the annealing process, while electron-acceptors like oxygen and nitric oxide gas retard it. Evidently, a donor-acceptor electron transfer takes place between the crystallite and the adsorbed molecules of the ambient gas or vapour. It supports an annealing mechanism invoking participation of free electrons.

Summar y We investigated the extraction of molybdenum into acetylacetone as a function of p H value, for the anions SO 4 2- , NO 3- , and CI - . From the results we derived prescriptions for the separation of molybdenum from mixtures of fission products.

Zusammenfassung Es wird über die Carboxylierung von Formiat bei Bestrahlung mit α-Strahlen (Radon) berichtet. Die Ausbeute des gebildeten Oxalates ist verhältnismäßig hoch und beträgt G (Oxalat) = 22,1 bei p H 9. In Gegenwart von n-Butanol bzw. Glyzerin als Konkurrenzpartner bei der Carboxylierung nimmt die Ausbeute des Oxalates stark ab. Für Radon samt Folgeprodukten wurde unter Berücksichtigung einer Reihe von Faktoren G (Fe 3+ ) = 10,5 errechnet.

A procedure is given for the simultaneous determination by neutron activation of gallium and germanium in iron meteorites or other similar materials. Germanium is separated from interfering activities by solvent extraction from 8 Ν HCl into carbon tetrachloride followed by distillation as GeCl 4 . The chemical yield is determined colorimetrically using phenylfluorone. Gallium is separated by repeated solvent extactions into isopropyl ether, and the yield is determined by flame photometry. About 12 man hours are necessary to process six to eight samples, not including the time necessary to reduce the counting data. The detection limits for a thermal-neutron flux of 10 12 cm -2 sec -1 are about 0.02 ppm germanium and 0.0001 ppm gallium.