Radiochemical studies of the sorption behavior of strontium and barium

The sorption behavior of strontium and barium on kaolinite, bentonite and chlorite-illite mixed clay was studied by radioanalytical techniques using the batch method.⁹⁰Sr (29.1 y) and¹³³Ba (10.5 y) were used as radiotracers. Characterization of the solid matrices was done by FTIR and XRD spectrometries and specific surface area measurements. Synthetic groundwater was used as the aqueous phase. The variation of the distribution ratioR _d, as a function of metal ion loading was examined. The sorption isotherms were fitted to various isotherm models. The sorption energies were calculated to be in the range of 8–10 kJ/mol suggesting an ion exchange type of sorption mechanism. In detailed experiments, chlorite-illite mixed clay was first presaturated with K⁺, Sr²⁺, Ca²⁺ and Al³⁺ ions, respectively, prior to sorption studies with Ba²⁺ ions. The results of Ca²⁺ pretreated chlorite-illite were very similar to those of natural chlorite-illite, suggesting that the Ba²⁺ ion exchanges primarily with the Ca²⁺ ion on the clay minerals.     

A structural study of calcium,strontium and barium crown ether complexes

Complexes involving the perchlorate, chloride, bromide or iodide salts of the heavy group 2 elements, calcium, strontium or barium, and either 15-crown-5 or 18-crown-6 have been synthesized and their X-ray crystal structures determined. A variety of coordination modes are presented between the crown ether and metal ions.     

The accumulation of radium,barium and lead in algae

A mixture of radium-224, lead-212 and barium-133 as well as a mixture of lead-210 and bismuth-210 were used for the investigation of these elements in algae Scenedesmus obliquus in dependence of equilibrium pH in the absence and in the presence of other salts. It has been found that the affinity constant K_M decreases in the following order (lg K_M values are given in parentheses): Ra²⁺ (5.1), Ba²⁺ (4.8), Sr²⁺ and Ca²⁺ (4.6), Mg²⁺ (4.2), Cs⁺, Rb⁺ and NH ₄ ⁺ (2.9), K⁺ (2.7), Na⁺ (2.6) and Li⁺ (2.4). The uptake of lead and bismuth is more complicated because of the accumulation of free cations as well as hydroxo complexes.     

Solution synthesis of calcium,strontium and barium metallocenes

Bis(cyclopentadienyl)metal complexes of calcium, strontium and barium can be prepared in synthetically useful yields (> 65%) from the reaction of lithium or potassium cyclopentadienides and the appropriate metal dihalides in THF. The THF-soluble complexes (C₅H₅)₂Ca(THF)₂ and (Me₅C₅)₂M(THF)₂ (M = Ca, Sr, Ba) are extracted from the reaction of the appropriate potassium cyclopentadienide with a metal halide; the THFinsoluble (C₅H₅)₂M(THF)_x(x ≈ 1 for Sr; x ≈ 0.25 for Ba) remain after the reaction of a lithium cyclopentadienide and the metal iodide.     

Non-cyclopentadienyl organometallic compounds of calcium, strontium and barium

The use of sterically demanding ligands has allowed the organometallic compounds of the heavy alkaline-earth metals calcium, strontium and barium to emerge from the shadow cast by the far better studied organomagnesium Grignard reagents. Metallocenes and other cyclopentadienyl-based complexes have been the most intensively investigated, but in the past decade a wealth of new non-cyclopentadienyl compounds have been characterized. A broad range of structure types are known, encompassing σ- and π-bound anionic ligands, and Lewis base adducts with neutral donors. In this review, crystallographically characterized complexes are discussed, and current interpretations of the bonding in heavier Group 2 element compounds are examined. Recent applications of non-cyclopentadienyl compounds in organic synthesis are surveyed.     

Monohydrates of strontium and barium hydroxide

The monohydrates of strontium and barium hydroxide have been prepared by decomposition, under vacuum, of the corresponding octahydrates. X-ray powder data for both compounds are reported, together with that for anhydrous strontium hydroxide; the latter is included in order to clarify an apparent anomaly in the literature.

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Zusammenfassung Es wurden die Monohydrate von Strontium und Bariumhydroxid im Vakuum aus den entsprechenden Octahydraten hergestellt. Röntgenographische Daten für beide Verbindungen sowie für wasserfreies Strontiumhydroxid wurden gegeben; für Letzteres, um gewisse Anom alien in der Literatur zu klären.

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Résumé Préparation des hydroxydes de strontium et de baryum monohydratés par décomposition dans le vide des octohydrates correspondants. Etude par rayons X de ces composés ainsi que de l'hydroxyde de strontium anhydre, dans le but, pour ce dernier, d'élucider certaines anomalies de la littérature.

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The authors wish to thank Mr. A. Miller for taking the X-ray powder photographs.     

Ion exchange of radium and barium in zeolites

The sorption of radium, barium and mixture of both elements has been studied in the zeolites 3A, 5A and Y. The ratio zeolite; solution was 100 mg: 10 cm³ and the pH was 3. Carrier-free radium was completely retained in all studied zeolites. When 0.0016 meq of barium/cm³ were added, the sorption of radium decreased in the zeolite 5A only and when 0.014 meq of barium/cm³, the radium sorption was reduced in all the studied zeolites. The sorption of barium was similar to that of radium. The amounts of sodium and calcium removed from the zeolites and the proton quantity fixed to them allowed us propose the ion exchange mechaniosm. The changes and ionic radii of the species exchanged did not play an important role. However, the location of the ions in the crystalline network of each zeolite is probably an important parameter for the exchange.     

Microdetermination of calcium, strontium and barium using the ring-oven method

Summary The ring-oven technique is recommended for the identification and determination of Ca, Sr and Ba in the micro scale. The elements are first converted into their nitrates and Ca is washed out by a mixture of absolute alcohol and ether. Sr is then separated from Ba as soluble diethyldithiocarbamidate in alcohol-ether. The rings obtained are developed by rhodizonate (Sr, Ba) and pyrogallol (Ca). Quantitative determinations are possible by comparison with standard rings. 0.60 g of Ca, 1.31 g of Sr and 8.24 g of Ba can be determined with an error lower than 6%.

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Zusammenfassung Zur Trennung und Bestimmung von Ca, Sr und Ba im Mikromaßstab wird die Ringofen-Technik empfohlen. Die drei Elemente werden dabei zunächst in die Nitrate übergeführt und Ca mit Äther-Alkohol ausgewaschen. Sr und Ba werden anschließend mit Diäthyldithiocarbamidat behandelt und Sr mit Äther-Alkohol abgetrennt. Die Identifizierung erfolgt mit Pyrogallol (Ca) bzw. Rhodizonat (Sr, Ba). Durch Vergleich mit Standardproben ist eine quantitative Bestimmung möglich. Hierbei können noch 0,60 g Ca, 1,31 g Sr und 8,24 g Ba mit einem Fehler < 6% erfaßt werden.

     

Rhodizonate as reagent for barium,strontium, and calcium

Summary The specificity and sensitivity of the spot tests for barium and strontium is improved by treating the brownish red rhodizonate fleck with a solution of dimethylamine hydrochloride. Calcium may be identified by the separation of characteristic crystals after adding a solution of rhodizonic and benzoic acids. A simple scheme of separation has been developed, which makes use of these confirmatory tests.

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Zusammenfassung Die Spezifität und Empfindlichkeit der Tüpfelproben für Barium und Strontium wird durch Behandlung des mit Natriumrhodizonat erhaltenen Tüpfelfleckes mit Dimethylaminhydrochlorid verbessert. Calcium kann durch die Abscheidung von charakteristischen Kristallen nachgewiesen werden, die nach Zugabe einer Lösung von Rhodizonsäure und Benzoesäure erhalten werden. Ein einfacher Trennungsgang wurde ausgearbeitet, der die nutzbringende Verwendung dieser Nachweisproben möglich macht.

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Résumé La spécificité et la sensibilité de la recherche du baryum et du strontium par essais à la touche sont améliorées en traitant la tache rouge brunâtre de rhodizonate par une solution de chlorhydrate de diméthylamine. Le calcium peut être identifié par la séparation de cristaux caractéristiques après addition d'une solution d'acides rhodizonique et benzoïque. On a mis au point un schéma simple de séparation dans lequel on fait usage de ces tests de confirmation.

     

Radiochemical microdetermination of Manganese, strontium and barium by ion-exchange

A rapid radiochemical ion-exchange method has been developed for the quantitative separation of microamounts of Mn, Sr and Ba in the presence of other elements with atomic numbers below 84. The method proposed, combined with neutron-activation analysis, has been successfully applied to the simultaneous determination of Mn, Sr and Ba in plant and animal tissues. The method is simple and accurate.     

The photolysis of barium and strontium azides

The effect of very high intensity UV light on powdered barium and strontium azides in vacuo in the temperature ranges −70° to 100°, and −80° to 90°, has been studied. The photolytic decompositions were characterized by a high percentage decomposition and sigmoid pressure vs time plots similar to those obtained by thermal decomposition. Kinetic analysis, the determination of activation energies, studies of the dependence of reaction rates on light intensity, and the effect of water vapour, were carried out. Mechanisms for decomposition over well defined temperature ranges are proposed.     

Densities of liquid metals: calcium,strontium, barium

Abstract

We report a method of measuring the densities of liquids at intermediate temperatures which employs Archimedes' Principle in a two-sinker arrangement. This method is then used to measure the densities of pure liquid calcium, strontium, and barium. We find ρ(Ca) = 1.4931 ? 1.37 × 10^?4 T(°C) from 850 ? 950°C, ρ(Sr) = 2.5547 ? 2.83 × 10^?4 T(°C) from 780 ? 880°C, and ρ(Ba) = 3.5561 ? 2.99 × 10^?4 T(°C) from 730 ? 830°C, where the units are gm/cm³. We use relations critical constants for these liquids to estimated dρ/dT, and compare these values of dρ/dT with those for other liquid metals; we also compare our results with recent x-ray diffraction data for these liquid metals.     

A kinetic study of the seeded growth of barium sulfate in the presence of additives

The crystallization of barium sulfate seed crystals in supersaturated solutions has been studied conductometrically and radiochemically at 25°C. After an initial surge reflecting secondary nucleation, the crystal growth follows a rate law second-order in relative supersaturation, both in the absence and presence of additives. Organic polyphosphonates and polymeric molecules such as polygalacturonic acid and ethylenemaleic anhydride co-polymer are effective inhibitors of crystallization. The inhibiting influence of benzene polycarboxylic acids can be related to the tendency for complex formation with barium ions and to the pH of the supersaturated solutions.     

Energetics of magnesium, strontium, and barium doped lanthanum gallate perovskites

LaGaO₃ perovskites doped with Sr or Ba at the La site and Mg at the Ga site were prepared by solid-state reaction or sol-gel method and characterized. Enthalpies of formation from constituent oxides at 298 K were determined by high-temperature oxide melt solution calorimetry. Energetic trends are discussed in terms of defect chemistry. As oxygen deficiency increases, formation enthalpies define three trends, LaGa_1−yMg_yO_3−δ (LGM), La_1−xSr_xGa_1−yMg_yO_3−δ (LSGM), and La_1−xBa_xGa_1−yMg_yO_3−δ (LBGM). They become less exothermic with increasing doping, suggesting a dominant destabilization effect from oxygen vacancies. The endothermic enthalpy of vacancy formation is 275±37, 166±18 and 138±12 kJ/mol of V_O^·· for LGM, LBGM and LSGM, respectively. Tolerance factor and ion size mismatch also affect enthalpies. In terms of energetics, Sr is the best dopant for the La site and Mg for the Ga site, supporting earlier studies, including oxygen ion conductivity and computer modeling.     

Reaction of strontium sulfate with anatase and rutile below and above the phase transition temperature of strontium sulfate

The solid-state reaction of strontium sulfate with anatase and rutile was examined by isothermal and non-isothermal TGA/DTA and X-ray diffraction. The endothermic peak due to the reversible phase transition of SrSO₄ was observed by DTA in the vicinity of the endothermic peak due to the reaction. The product was only SrTiO₃ in all cases. The reaction mechanism was described by the Jander model. The rate constant for anatase was about twice as large as that for rutile. The relation between In k_j and T⁻¹ for anatase and rutile was discontinuous being linear either side of the phase transition temperature of SrSO₄. The rate constant just above the transition temperature was enhanced 1.5 times with respect to that just below the temperature. The activation energy for the reaction of strontium sulfate with rutile was 354 and 435 kJ mol⁻¹ in the higher and lower temperature regions respectively. In the reaction with anatase, the phase transition of anatase to rutile was also observed in about 30% of the fraction reacted at any temperature, and the rate constant was scattered from the In k_j vs. T⁻¹ curve, especially at high temperatures.