Estado químico del arsénico formado por transformaciones nucleares en compuestos inorgánicos de germanio, selenio, bromo y arsénico

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The distribution of radioactive arsenic among trivalentand pentavalent states of arsenic produced by nuclear transformationshas been investigated in simple inorganic compoundsof germanium, selenium, bromine and arsenic. In some cases wehave studied the change of this distribution by annealing proces...

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Autor principal: Baró, Gregorio Bonifacio
Formato: Tesis Doctoral
Lenguaje:Español
Publicado: 1961
Acceso en línea:https://hdl.handle.net/20.500.12110/tesis_n1096_Baro
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id todo:tesis_n1096_Baro
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spelling todo:tesis_n1096_Baro2023-10-03T12:16:30Z Estado químico del arsénico formado por transformaciones nucleares en compuestos inorgánicos de germanio, selenio, bromo y arsénico Baró, Gregorio Bonifacio The distribution of radioactive arsenic among trivalentand pentavalent states of arsenic produced by nuclear transformationshas been investigated in simple inorganic compoundsof germanium, selenium, bromine and arsenic. In some cases wehave studied the change of this distribution by annealing processes. The nuclear transformations we have studied are thefollowing: Ge77-—β—> As77 Se76 (n,p) As76 Br81 (n,α) As78 Br79 (n,α) As76 As75 (n,γ) As76 The compounds were irradiated with neutrons in the RAIreactor in Buenos Aires and later with neutrons obtained bybombarding beryllium with 26 MeV deuterons in the Philipssynchrocyclotron of Amsterdam. The chemical separations used consisted of the dissolutionof the irradiated compound in a solution containing AsIIIand AsV carriers. The arsenate fractions were separated fromthe arsenite fractions by precipitation as magnesium ammoniumarsenate. The arsenite was then oxidized to arsenate which inturn was precipitated as magnesium ammonium arsenate. Allfractions were converted to magnesium piro-arsenate. The radioactive samples were counted with an end-window G.M. counter under conditions of standard geometry. Annealing was carried out in constant-temperature bathsduring specified periods of time. It is evident from our experimental results that chemicalconditions in the aqueous medium, and specially the pH,have little or no influence on the distribution of the arsenicactivity among the two oxidation states. This suggests thatthe final form in which the radioactive arsenic will be foundis already determined inside the target lattice. It is even more striking that the distribution observedin GeO2 is very nearly equal to that in SeO2. This suggeststhat the structure of the oxide is the determining factorfor the distribution of the arsenic activity among arseniteand arsenate fractions. It is very curious that the AsV: total As of radioactive arsenic in the oxides of germanium andselenium and in the oxides of arsenic may be represented asa linear function of the oxygen: parent element ratio forthe irradiated compound. This is true for some other compoundsas Na2Se04 and Na2Ge03. In the other compounds that we haveinvestigated the linear relationship does not hold very well. In part this maybe the reflection of the differences in thelattice arrangement, but reducing and oxidizing tendenciesof the irradiated compounds may also possibly play a role. The differences found between Na2Se03 and H2Se03 can be ascribedto bound hydrogen present inside the latter compound. The results in the bromine compounds indicate that thedistribution of radioactive arsenic among the arsenite andarsenate fractions depends on the amount of oxygen containedin the irradiated compounds. Even in the bromides the percentageof radioarsenic is fairly directly correlated with theoxygen present as water in the crystal. Annealing turned out to be quite slow, even at temperaturesappreciably higher than those required to increase theretention in most neutron irradiated solid salts. The first part of this thesis presents a survey of thefield of Szilard-Chalmers and similar phenomena with emphasison inorganic systems. It will not cite all the literaturepublished until now, but will try to review some of the mostsignificant recent work. Fil: Baró, Gregorio Bonifacio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 1961 Tesis Doctoral PDF Español info:eu-repo/semantics/openAccess https://creativecommons.org/licenses/by-nc-sa/2.5/ar https://hdl.handle.net/20.500.12110/tesis_n1096_Baro
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
language Español
orig_language_str_mv Español
description The distribution of radioactive arsenic among trivalentand pentavalent states of arsenic produced by nuclear transformationshas been investigated in simple inorganic compoundsof germanium, selenium, bromine and arsenic. In some cases wehave studied the change of this distribution by annealing processes. The nuclear transformations we have studied are thefollowing: Ge77-—β—> As77 Se76 (n,p) As76 Br81 (n,α) As78 Br79 (n,α) As76 As75 (n,γ) As76 The compounds were irradiated with neutrons in the RAIreactor in Buenos Aires and later with neutrons obtained bybombarding beryllium with 26 MeV deuterons in the Philipssynchrocyclotron of Amsterdam. The chemical separations used consisted of the dissolutionof the irradiated compound in a solution containing AsIIIand AsV carriers. The arsenate fractions were separated fromthe arsenite fractions by precipitation as magnesium ammoniumarsenate. The arsenite was then oxidized to arsenate which inturn was precipitated as magnesium ammonium arsenate. Allfractions were converted to magnesium piro-arsenate. The radioactive samples were counted with an end-window G.M. counter under conditions of standard geometry. Annealing was carried out in constant-temperature bathsduring specified periods of time. It is evident from our experimental results that chemicalconditions in the aqueous medium, and specially the pH,have little or no influence on the distribution of the arsenicactivity among the two oxidation states. This suggests thatthe final form in which the radioactive arsenic will be foundis already determined inside the target lattice. It is even more striking that the distribution observedin GeO2 is very nearly equal to that in SeO2. This suggeststhat the structure of the oxide is the determining factorfor the distribution of the arsenic activity among arseniteand arsenate fractions. It is very curious that the AsV: total As of radioactive arsenic in the oxides of germanium andselenium and in the oxides of arsenic may be represented asa linear function of the oxygen: parent element ratio forthe irradiated compound. This is true for some other compoundsas Na2Se04 and Na2Ge03. In the other compounds that we haveinvestigated the linear relationship does not hold very well. In part this maybe the reflection of the differences in thelattice arrangement, but reducing and oxidizing tendenciesof the irradiated compounds may also possibly play a role. The differences found between Na2Se03 and H2Se03 can be ascribedto bound hydrogen present inside the latter compound. The results in the bromine compounds indicate that thedistribution of radioactive arsenic among the arsenite andarsenate fractions depends on the amount of oxygen containedin the irradiated compounds. Even in the bromides the percentageof radioarsenic is fairly directly correlated with theoxygen present as water in the crystal. Annealing turned out to be quite slow, even at temperaturesappreciably higher than those required to increase theretention in most neutron irradiated solid salts. The first part of this thesis presents a survey of thefield of Szilard-Chalmers and similar phenomena with emphasison inorganic systems. It will not cite all the literaturepublished until now, but will try to review some of the mostsignificant recent work.
format Tesis Doctoral
author Baró, Gregorio Bonifacio
spellingShingle Baró, Gregorio Bonifacio
Estado químico del arsénico formado por transformaciones nucleares en compuestos inorgánicos de germanio, selenio, bromo y arsénico
author_facet Baró, Gregorio Bonifacio
author_sort Baró, Gregorio Bonifacio
title Estado químico del arsénico formado por transformaciones nucleares en compuestos inorgánicos de germanio, selenio, bromo y arsénico
title_short Estado químico del arsénico formado por transformaciones nucleares en compuestos inorgánicos de germanio, selenio, bromo y arsénico
title_full Estado químico del arsénico formado por transformaciones nucleares en compuestos inorgánicos de germanio, selenio, bromo y arsénico
title_fullStr Estado químico del arsénico formado por transformaciones nucleares en compuestos inorgánicos de germanio, selenio, bromo y arsénico
title_full_unstemmed Estado químico del arsénico formado por transformaciones nucleares en compuestos inorgánicos de germanio, selenio, bromo y arsénico
title_sort estado químico del arsénico formado por transformaciones nucleares en compuestos inorgánicos de germanio, selenio, bromo y arsénico
publishDate 1961
url https://hdl.handle.net/20.500.12110/tesis_n1096_Baro
work_keys_str_mv AT barogregoriobonifacio estadoquimicodelarsenicoformadoportransformacionesnuclearesencompuestosinorganicosdegermanioseleniobromoyarsenico
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