Electropolymerized coatings of polyaniline on copper by using the galvanostatic method and their corrosion protection performance in HCl medium

The synthesis of polyaniline coatings on the copper (Cu) surface has been investigated by using the galvanostatic method. The synthesized coatings were characterized by Fourier transform infrared spectroscopy, UV–visible absorption spectrometry and scanning electron microscopy. The anticorrosion performances of polyaniline coatings were investigated in 0.5 M HCl medium by the potentiodynamic polarization technique and electrochemical impedance spectroscopy. The corrosion rate of polyaniline‐coated Cu was found to be ～27 times lower than bare Cu, and potential corrosion increased from ?0.21 V versus Ag/AgCl for uncoated Cu to ?0.19 V versus Ag/AgCl for polyaniline‐coated Cu electrodes. Electrochemical measurements indicate that polyaniline coating has good inhibiting properties with a mean efficiency of ~96% at 10 mAcm^?2 current density applied on Cu corrosion in acid media. The results of this study clearly ascertain that the polyaniline has an outstanding potential to protect Cu against corrosion in an acidic environment. Copyright © 2014 John Wiley & Sons, Ltd.     

Characteristic of the Ag(bipy) 2 2+ /Ag(bipy) 2 + and Ag(phen) 2 2+ /Ag(phen) 2 + systems in acetonitrile

The values of standard potentials of redox systems formed by the complexes of Ag(II) and Ag(I) with 2,2-bipyridine and 1,10-phenanthroline in acetonitrile have been determined. The properties of the above systems in water and acetonitrile are compared. The possibility of application of these systems for the construction of electrodes with a constant potential in different solvents is discussed.

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Charakteristik der Systeme Ag(bipy) ₂ ²⁺ /Ag(bipy) ₂ ⁺ und Ag(phen) ₂ ²⁺ /Ag(phen) ₂ ⁺ in Acetonitril

Zusammenfassung Die Standardpotentialwerte der Redoxsysteme, die durch Komplexbildung von Ag(II)- und Ag(I)-Ionen mit 2,2-Bipyridin und 1,10-Phenantrolin gebildet werden, wurden in Acetonitril bestimmt. Die Eigenschaften dieser Redoxsysteme in Wasser und Acetonitril wurden verglichen.Es wurde weiterhin die Möglichkeit der Anwendung dieser Systeme zur Konstruktion einer Elektrode mit unveränderbarem Potential in verschiedenen Lösungsmitteln diskutiert.

     

Characteristic of the Ag(II)/Ag(I) system in the presence of 2-pyridinecarboxylic acid in acetonitrile

Summary Formation constants of the complexes of Ag(I) with 2-pyridine-carboxylic acid (Hpic) were determined by the potentiometric method: ₀₁=36, ₀₂=537. It was shown by IR spectroscopy that the complexation of Ag(I) ions in acetonitrile proceeds without the formation of Ag-O bond and the complexes have the following forms: AgHpic ⁺ and Ag(Hpic) ₂ ⁺ . Oxidation of Ag(Hpic) ₂ ⁺ at the potential =1850 mV vs. NHE resulted in the complex Ag(Hpic) ₂ ²⁺ . The formal potentialE _f ⁰ =1.772 V vs. NHE of the system Ag(Hpic) ₂ ²⁺ +eAg(Hpic)⁺+Hpic was determined by chronovoltamperometry, while the formal potentialE _f ⁰ =1.841 V vs. NHE of the system Ag(Hpic) ₂ ²⁺ +eAg(Hpic) ₂ ⁺ was calculated. Properties of the system in water and acetonitrile were compared.

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Charakteristik des Ag(II)/Ag(I)-Systems in Gegenwart von 2-Pyridincarbonsäure in Acetonitril

Zusammenfassung Es wurden die Bildungskonstanten der Komplexe von Ag(I) mit 2-Pyridincarbonsäure (Hpic) mittels Potentiometrie bestimmt: ₀₁=36, ₀₂=537. Die IR-Spektren bewiesen, daß die Komplexierung von Ag(I)-Ionen über die Ausbildung einer Ag-O-Bindung verläuft, wobei die Komplexe die folgenden Formeln besitzen: AgHpic ⁺ und Ag(Hpic) ₂ ⁺ . Die Oxidation von Ag(Hpic) ₂ ⁺ beim Potential =1850 mV gegenüber NHE ergab den Komplex Ag(Hpic) ₂ ²⁺ . Das formale PotentialE _f ⁰ =1.772 V (gegenüber NHE) des Systems Ag(Hpic) ₂ ²⁺ +eAg(Hpic)⁺+Hpic wurde mittels Chronovoltamperometrie ermittelt, während das formale PotentialE _f ⁰ =1.841 V (gegenüber NHE) des Systems Ag(Hpic) ₂ ²⁺ +eAg(Hpic) ₂ ⁺ berechnet wurde. Außerdem wurden die Eigenschaften der Systeme in Wasser und Acetonitril verglichen.

     

Characteristic of the Ag(II)/Ag(I) system in the presence of 2,2′:6′,2″-terpyridine in acetonitrile

Summary Composition of complexes of Ag(II) and Ag(I) ions with 2,2:6,2-terpyridine (tp) have been established. It has been found that the Ag⁺ ion forms only one complex Ag(tp)⁺ withtp in acetonitrile; its conditional formation constant: ₀₁=6.6·10⁴ has been determined by the potentiometric method. Equilibria and redox systems formed in solutions due to the complexation of Ag⁺ and Ag²⁺ and oxidation of Ag(II) complexes are described. Their formal potentials have been found by coulometric and voltamperometric examinations. The presence of the Ag(tp) ₂ ³⁺ ion in the anodic oxidized solutions of the complexes Ag(tp)(NO₃)₂ and Ag(tp)₂(NO₃)₂ has been proved. Properties of the system Ag(II)/Ag(I) in the presence of terpyridine in water and in acetonitrile have been compared.

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Charakteristik der Systeme Ag(II)/Ag(I) in Gegenwart von 2,2:6,2-Terpyridin in Acetonitril

Zusammenfassung Die Zusammensetzung der Komplexe von Ag(I)- und Ag(II)-Ionen mit 2,2:6,2-Terpyridin (tp) wurde bestimmt. Das Ag⁺-Ion bildet mittp in Acetonitril nur einen Komplex-Ag(tp)⁺. Seine Konditionalbildungskonstante ₀₁=6.6·10⁴ wurde mit Hilfe der potentiometrischen Methode bestimmt. Es wurden die Gleichgewichte und Redoxsysteme als Resultat der Komplexbildung von Ag(II)- und Ag(I)-Ionen und der Ag(II)-Komplexoxidation charakterisiert und die Formalpotentiale mittels Voltametrie und Coulometrie bestimmt. Die Gegenwart der Ag(tp) ₂ ³⁺ -Ionen wurde in anodisch oxydierten Lösungen der Komplexe Ag(tp)(NO₃)₂ und Ag(tp)₂(NO₃)₂ nachgewiesen. Die Eigenschaften des Systems Ag(II)/Ag(I) in Gegenwart von 2,2:6,2-Terpyridin in Wasser und in Acetonitril wurden verglichen.

     

Extraction-chromatographic system TBP-HBr in radiochemical neutron activation analysis of high-purity materials

The extraction and extraction-chromatographic behaviour of a variety of elements in the TBP-HBr system with concentrations from 0.1 to 7M HBr has been studied. The results allowed the development of simple procedures for radiochemical neutron activation determination of 22 impurity elements (Na, K, Sc, Cr, Mn, Fe, Co, Ni, Cu, Ga, As, Se, Rb, Sr, Zn, Mo, Ag, Sb, Te, Ba, La, Hf and W) in high-purity cadmium and indium samples with detection limits from 1 g g^–1 for Fe and Zr to 0.01 ng g^–1 for Na, Sc, Mn with relative standard deviations < 0.15. To increase the selectivity of the extraction-chromatographic separation, use was made of extraction suppression and co-extraction effects. The procedure for the extraction-chromatographic separation of scandium from a number of other elements is described as an example. The procedure can be used for simultaneous quantitative separation of impurity radionuclides from radiation produced long-life scandium radionuclides in the neutron activation analysis of titanium and vanadium.     

Trace element determination in seawater by ICP-SFMS coupled with a microflow nebulization/desolvation system

Direct and simultaneous determination of Al, Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Sb, U, V and Zn in diluted (1:10 v:v) seawater from the Antarctic Ocean and the Venice Lagoon at the ng mL^–1 and pg mL^–1 level has been performed by using an inductively coupled plasma sector field mass spectrometer (ICP-SFMS). Samples were analysed by using a PFA microflow nebulizer coupled with a desolvation system or a PFA microflow nebulizer coupled with a Teflon spray chamber, respectively. Measurements were carried out at low (LR, m/m=300), medium (MR, m/m=3,000) and high (HR, m/m=7,500) resolutions depending on the studied isotope. To avoid contamination, sample pre-treatment was carried out in a clean laboratory equipped with a Class 100 vertical laminar flow hood. Concentration ranges (minimum–maximum in ng mL^–1) found in the Antarctic seawater samples (in depth profiles) were: Ag 0.0004–0.0018, As 0.69–1.32, Cd 0.031–0.096, Co 0.018–0.065, Cr 0.18–0.46, Cu 0.04–1.58, Fe 0.13–1.63, Mn 0.02–0.12, Mo 5.97–12.46, Pb 0.007–0.074, Sb 0.033–0.088, U 0.5–1.9, V 0.6–2.5 and Zn 0.16–0.80. Concentration ranges (min–max in ng mL^–1) found in the Venice Lagoon water samples (temporal profile from a benthic chamber experiment) were: Al 0.24–0.61, Ag 0.007–0.031, As 1.42–2.27, Cd 0.050–0.182, Co 0.440–1.461, Cr 0.15–0.34, Cu 0.81–2.46, Fe 0.25–1.66, Mn 11.6–31.7, Mo 6.50–10.6, Pb 0.047–0.225, Sb 0.240–0.492, U 1.7–3.3, V 1.3–2.8 and Zn 5.20–21.5. The detection limits range between 0.06 pg mL^–1 for Ag and U to 15 pg mL^–1 for Fe. In order to check the accuracy of the analytical procedure, measurements of the trace elements in a certified reference material (coastal Atlantic seawater, CASS-4-NRCC) were compared with the certified values. In addition, the results from the Antarctic and Venice Lagoon samples were compared with those obtained by using different analytical techniques.     

Complexing equilibria and redox potentials in the system Ag(II)/Ag(I)-1,10-phenanthroline in propylene carbonate

Predominance areas of various equilibria were identified and complex formation constants of Ag(I) with 1,10-phenanthroline were determined as well as the solubility product of the complex salt for Ag(phen)₂ClO₄ in propylene carbonate. The solubility product of AgNO₃ in propylene carbonate was estimated. The value of the formal potential of the system Ag(phen) ₂ ²⁺ /Ag(phen) ₂ ⁺ inPC was determined by chronovoltammetry. Differences in the stability of analogous complexes in water andPC are discussed.

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Die Gleichgewichtskonstante der Komplexierung und die Redoxpotentiale im System Ag(II)/Ag(I)-1,10-Phenantrolin in Propylencarbonat

Zusammenfassung Die Gebiete der Dominanz der einzelnen Gleichgewichte, die Bildungskonstanten ₁ und ₂ der Komplexe Ag(I) mit 1,10-Phenantrolin und der Wert des Löslichkeitsproduktes Ag(phen)₂ClO₄ in Propylencarbonat wurden bestimmt. Das Löslichkeitsprodukt von AgNO₃ in Propylencarbonat wurde abgeschätzt. Die Werte des formalen Potentials des Systems Ag(phen) ₂ ²⁺ /Ag(phen) ₂ ⁺ inPC wurden mit Hilfe cyclischer Voltametrie ermittelt. Es wurden weiterhin die Unterschiede in der Stabilität analoger Komplexe in Wasser und in Propylencarbonat diskutiert.

     

Electron spectroscopic investigation (AES/SAM, XPS) of electroplated Ag layers on LED-CuSn-lead frames: Combined phenomena of segregation and corrosion

Summary In order to improve LED fabrication processes inclusive handling in LED packaging and final tinning details of two interlinked phenomena were studied by the use of AES/SAM and XPS: Cu segregation during low-temperature thermal stress as well as different stages of (Cl, S) corrosion which take place at the surface of Ag thin films electroplated on lead frames consisting of CuSn material. In the case of the Ag corrosion a probable mechanism was observed, namely that the initial step is connected with an enlarged presence of Cl in the topmost corrosion layer. In subsequent steps this chlorinated Ag thin film was substituted by sulphatic, afterwards sulphidic silver at the surface. In Ag material adjacent to the Cu segregates all corrosive processes proceed in an especial intense manner, which is demonstrated by the fact, that the Cu-necks induced by the segregation process quickly and intensively include deeper located Ag regions into the corrosion process.     

Lumineszierende Cu(I)-, Ag(I)- und Tl(I)-Komplexe mit N-Butyl-N′-benzolsulfonylthioharnstoff- Tetra- und hexamere (ML)x-Cluster

Zusammenfassung Das Säureanion von N-Butyl-N-benzolsulfonylthioharnstoff (BuBsT) bildet mit Cu(I) einen lumineszierenden hexameren und einen nicht lumineszierenden tetrameren Cluster (Cu(BuBsT))_x; x=6, 4. Röntgenstrukturanalysen belegen für x=6 eine verzerrt oktaedrische und für x=4 eine verzerrt tetraedrische Anordnung der Cu-Atome. Die Liganden beider Cluster sind über den Thioharnstoff-Schwefel und den Sulfonamid-Stickstoff mit den Cu-Atomen verknüpft (S,N-Koordination). Jeweils ein Sulfonyl-Sauerstoffatom pro Ligand bildet eine intramolekulare Wasserstoffbrücke zu der NHC₄H₉-Gruppe der gleichen Ligandeinheit aus. Ag(BuBsT) tritt in Form von drei lumineszierenden Modifikationen auf, von denen eine (Ag(BuBsT)-II) hexamer ist (isotyp mit (Cu(BuBsT))₆). Tl(BuBsT) liegt in CHCl₃-Lösung überwiegend als Dimer vor.

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Luminescent Cu(I)-, Ag(I)- and TI(I)-complexes with N-Butyl-N-benzenesulfonylthiourea-tetramer and hexamer (ML)_x-clusters

Summary The acid anion of N-butyl-N-benzenesulfonylthiourea (BuBsT) forms numerous 1/1 complexes with the univalent ions Cu(I), Ag(I) and Tl(I). The crystal structures of two different copper(I) clusters (Cu(BuBsT))_x, (x=6, 4) are discussed. The hexamer containing a distorted Cu₆ octahedron is luminescent, while the analogous tetramer containing a distorted Cu₄ tetrahedron is not. The copper atoms of both clusters form coordinate linkages with the sulfonamide nitrogen and the thiourea sulphur of the ligands (S,N-coordination). One sulfonyl oxygen per ligand is bound to the NHC₄H₉ group of the same ligand through a hydrogen bond. Ag(BuBsT) forms three different luminescent modifications. One of them (Ag(BuBsT)-II) is isotype to (Cu(BuBsT))₆ and therefore hexamer, too. Tl(BuBsT) mainly forms dimers in CHCl₃ solution.

     

Structural Characterization of Some Coinage Metal(I) Thiosulfate Complexes, $\rm M^{1}_{a}M\rm ^{2}_{b}(X_{c}) (S_{2}O_{3})_{d}(\cdot eS)$ (M1 = Group 1 Cation,X = Univalent Anion,M2 = CuI,AgI, S = Solvent)

Building on previous single crystal X‐ray structure determinations for the group 1 salts of complex thiosulfate/univalent coinage metal anions previously defined for (NH₄)₉AgCl₂(S₂O₃)₄, NaAgS₂O₃·H₂O and Na₄[Cu(NH₃)₄][Cu(S₂O₃)₂]·NH₃, a wide variety of similar salts, of the form , M¹ = group 1 metal cation, M² = univalent coinage metal cation (Cu, Ag), (X = univalent anion), most previously known, but some not, have been isolated and subjected to similar determinations. These have defined further members of the isotypic, tetragonal series, for M¹ = NH₄, M² = Cu, Ag, X = NO₃, Cl, Br, I, together with the K/Cu/NO₃ complex, all containing the complex anion [M²(SSO₃)₄]^7? with M² in an environment of symmetry, Cu, Ag‐S typically ca. 2.37, 2.58Å, with quasi‐tetrahedral S‐M‐S angular environments. Further salts of the form , n = 1‐3, have also been defined: For n = 3, M² = Cu, M¹/x = K/2.25 or 1 5/6, NH₄/6, (and also for the (NH₄)₄Na/4H₂O·MeOH adduct) the arrays take the form with distorted trigonal planar CuS₃ coordination environments, Cu‐S distances being typically 2.21Å, S‐Cu‐S ranging between 105.31(4)–129.77(4)°; the silver counterparts take the form for M¹ = K, NH₄. For n = 2, adducts have only been defined for M² = Ag, the anions of the M¹ = Na, K adducts being dimeric and polymeric respectively: Na₆[(O₃SS)₂Ag(μ‐SSO₃)₂Ag(SSO₃)]·3H₂O, K₃[Ag(μ‐SSO₃)₂]_(∞|∞)·H₂O; a polymeric copper(I) counterpart of the latter is found in Na₅Cu(NO₃)₂(S₂O₃)₂ ≡ 2NaNO₃·Na₃[Cu(μ‐SSO₃)₂]_(∞|∞). For n = 1, NaAgS₂O₃, the an‐ and mono‐ hydrates, exhibit a two‐dimensional polymeric complex anion in both forms but with different contributing motifs. (NH₄)₁₃Ag₃(S₂O₃)₈·2H₂O takes the form (NH₄)₁₃[{(O₃SS)₃Ag(μ‐SSO₃)}₂Ag], a linearly coordinated central silver atom linking a pair of peripheral [Ag(SSO₃)₄]^7? entities. In Na₆[(O₃SS)Ag(μ‐SSO₃)₂Ag(SSO₃)]·3H₂O, the binuclear anions present as Ag₂S₄ sheets, the associated oxygen atoms being disposed to one side, thus sandwiching layers of sodium ions; the remarkable complex Na₅[Ag₃(S₂O₃)₄]_(∞|∞)·H₂O is a variant, in which one sodium atom is transformed into silver, linking the binuclear species into a one‐dimensional polymer. In (NH₄)₈[Cu₂(S₂O₃)₅]·2H₂O a binuclear anion of the form [(O₃SS)₂Cu(μ‐S.SO₃)Cu(SSO₃)₂]^8? is found; the complex (NH₄)₁₁Cu(S₂O₃)₆ is 2(NH₄)₂(S₂O₃)·(NH₄)₇[Cu(SSO₃)₄]. A novel new hydrate of sodium thiosulfate is described, 4Na₄S₂O₃·5H₂O, largely describable as sheets of the salt, shrouded in water molecules to either side, together with a redetermination of the structure of 3K₂S₂O₃·H₂O.     

Kristallstruktur von Trisilber(I)amidosulfat Monohydrat,Ag3SO3N · H2O

An X-ray crystal structure analysis of yellow Ag₃SO₃N · H₂O was carried out at room temperature:M=435.69, monoclinic, P2₁/n,a=11.628 (5) Å,b=8.058 (4) Å,c=12.034 (5) Å, =86.49 (3)°,V=1125.5 ų,Z=8,d _x =5.142 Mgm^–3, MoK, =0.71069 Å (graphite monochromator), =10.5 mm^–1,R=5.44%,R _w =5.85% (877 reflections, 118 parameters). The structure contains Ag planes with Ag-Ag distances shorter than in metallic silver. The nitrogen atoms of the SO₃N anion are covalently bonded to 4Ag atoms of these Ag planes, thus assuming the extraordinary coordination number of 5. The five crystallographically independent Ag atoms forming the Ag planes have approximate linear N-Ag-N coordination. In addition, the structure contains two Ag atoms which are ionically coordinated to 4 resp. 5O atoms of SO₃N and water. The colour-structure correlation of Ag(I) compounds with colourless anions is discussed.

Herrn Prof. Dr. mult.V. Gutmann zum 65. Geburtstag gewidmet.     

Spectral and electrochemical investigations of copper(II)N-salicylidene-amino acidato complexes and their imidazole,pyrazole and pyridine adducts

Summary Copper(II) Schiff base complexes derived from salicylaldehyde and amino acids such as glycine, L-alanine, L-serine, L-threonine, and -alanine, Cu(sal-aa)(H₂O) and their imidazole, pyrazole and pyridine adducts, Cu(sal-aa)L have been prepared. Their electronic spectral and e.s.r. data in water concur with information obtained in dioxane-H₂O mixtures; cyclic voltammetric (c.v.) and differential pulse voltammetric (d.p.v.) data were collected in aqueous media; based on the experimental data, a three-step electrode mechanism has been proposed. In pH 5-3.5 the presence of protonated species, [Cu(sal-aaH)(H₂O)]⁺ is evident from c.v. profiles. The electronic spectra of Cu(sal-aa)L adducts show a shift ofca. 10–20 nm in the d-d band position to lower wavelengths. E.s.r. parameters g_iso, g and A are lower and A_iso higher for the adducts compared to the parent complexes. These changes are commensurate with increased planar covalency resulting from the replacement of H₂O molecules by N-donor ligands. The electrochemical behaviour of pyridine adducts is similar to that of Cu(sal-aa)(H₂O) complexes. Imidazole and pyrazole adducts show irreversible one-electron reduction, this difference in electrochemical behaviour being related to the difference in electron acceptor ability of the N-donor ligands. At low pHs, the electrochemical behaviour of the adducts is similar to that of the parent complexes.     

Complexing equilibria and redox potentials of the Ag(II)/Ag(I) system in the presence of 2,2′:6′,2″-terpyridine in water

Summary The conditional protonation constants (=0.1) for 2,2:6,2-terpyridine, logK ₁=4.93, logK ₂=3.69, were determined by thepH-metric method. The compositions of complexes of Ag²⁺ and Ag⁺ ions with 2,2:6,2-terpyridine (tp) were studied and equilibria of the complex formation process were described. The values of conditional complex formation constants are as follows: for Ag(tp) ₂ ⁺ :log₀₁=5.79, log₀₂=9.68, for Ag(tp) ₂ ²⁺ :log₀₂=25.31, while the conditional constant of the Ag(tp)NO₃ precipitate formation is:K _SO=2.45·10⁴. Using coulometric and chronovoltamperometric measurements, the redox systems being formed in the complex solutions of Ag(II) and Ag(I) were determined and described including their formal potentials.

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Komplexibildungsgleichgewichte und Redoxpotentiale des Systems Ag(II)/Ag(I) in Gegenwart von 2,2:6,2-Terpyridin in Wasser

Zusammenfassung Mit Hilfe derpH-metrischen Methode wurden die konditionalen Protonationskonstanten (=0.1) von 2,2:6,2-Terpyridin bestimmt: logK ₁=4.93, logK ₂=3.69. Es wurde auch die Zusammensetzung der Komplexe von Ag(II) und Ag(I) mit 2,2:6,2-Terpyridin(tp) bestimmt sowie die Gleichgewichte der komplexbildung beschrieben. Die Werte der Konditionalkomplexbildungskonstanten sind: für Ag(tp) ₂ ⁺ :log₀₁=5.79, log₀₂=9.68, für Ag(tp) ₂ ²⁺ :log₀₂=25.31 und für das Löslichkeitsprodukt Ag(tp)NO₃:K _SO ^–1 =4.08·10^–5. Die in Komplexlösungen von Ag(II) und Ag(I) vorliegenden Redoxsysteme wurden mittels cyclischer Voltametrie und Coulometrie untersucht und die Formalpotentialwerte dieser Systeme in Wasser bestimmt.

     

Aktivierungsanalytische Gem?ldeuntersuchungen

Zusammenfassung Aktivierungsanalytisch wurden die Spurengehalte an Mn, Cu, Ba, Cr, Ag und Sb im Bleiweiß von Gemälden der Alten Pinakothek bestimmt. In Modellversuchen wurde ein aus radiochemischer Trennung und -Spektrometrie kombiniertes Analysenverfahren ausgearbeitet. Die Nachweisgrenzen lagen bei 5 · 10^–10 g für Ba, 2 · 10^–10 g für Cr, 10^–10 g für Ag und Cu, 10^–11 g für Mn und Sb. Für eine Analyse standen zum Teil nur 10 g Bleiweiß zur Verfügung. Es wurde vorwiegend Bleiweiß aus Gemälden venezianischer und niederländischer Meister des 16. und 17. Jahrhunderts analysiert, wobei sich eindeutige Unterschiede im Mn-, Ag- und Sb-Gehalt von venezianischem und niederländischem Bleiweiß ergaben. Modernes und altes Bleiweiß zeigen große Unterschiede vor allem im Cu- und Ba-Gehalt; dies kann zur Fälschungserkennung dienen.

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Summary Trace concentrations of Mn, Cu, Ba, Cr, Ag, and Sb in white-lead samples of paintings of the Alte Pinakothek were determined by activation analysis. In model experiments an analytical method comprising radiochemical separation and -spectroscopy was developed. The limits of identification were about 5 · 10^–10 g for Ba, 2 · 10^–10 g for Cr, 10^–10 g for Ag and Cu, 10^–11 g for Mn and Sb. Partly there were available only 10 g of white lead for one analysis. Predominately white-lead samples from paintings of Venetian and Dutch masters of the 16th and 17th centuries were analysed. In these samples unambiguous differences were found in the Mn, Ag, and Sb concentrations. Modern and old white lead show great differences mainly in Cu and Ba concentrations; this may be used for the recognition of forgeries.

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Auszugsweise vorgetragen auf der Tagung in Lindau. Lux, F., u. L. Braunstein: Angew. Chem. 78, 720 (1966).

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Auszug aus der von der Fakultät für Allgemeine Wissenschaften der Technischen Hochschule München genehmigten Dissertation über Die aktivierungsanalytische Bestimmung des Spurengehaltes im Bleiweiß von Gemälden der Alten Pinakothek des Dipl.-Chem. Lothar Braunstein.

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Herrn Dr. H. Kühn vom Doerner-Institut für Konservierung und naturwissenschaftliche Untersuchung von Kunstwerken, München, sind wir für zahlreiche wertvolle Anregungen, besonders bei der Auswahl der Gemälde, sowie für die Beschaffung der Analysenproben zu besonderem Dank verpflichtet.

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Herrn Prof. Dr. H.-J. Born danken wir herzlich für die Unterstützung dieser Arbeit. Der Bestrahlungsgruppe des FRM unter Leitung von Herrn Dipl.-Phys. G. Rau danken wir für die sorgfältige Durchführung der Bestrahlungen.Dem Bundesministerium für wissenschaftliche Forschung und der Deutschen Forschungsgemeinschaft gilt unser Dank für finanzielle Unterstützung.     

Saturation and fragmentation in non resonant laser postionization of sputtered atoms and molecules

Summary Using non resonant two photon ionization at =248 nm, the emission of neutral atoms and dimers was investigated during ion beam sputtering of polycrystalline silver and copper with 5 keV Ar⁺. Saturation effects were examined by measuring the ion intensities as a function of the photon flux density. It is found that with the maximum available laser power density (1·10⁹ W/cm²) the ionization of Ag atoms can be easily saturated, whereas no complete saturation was achieved for Cu atoms. At the same time the saturation curve measured for Ag differs significantly both from that measured for Cu and from the theoretically expected behaviour for non resonant two photon ionization. For Ag₂ and Cu₂ the ionization is shown to be strongly resonance enhanced already being saturated in the region of 10⁷ W/cm². From the data taken at low laser power densities (<10⁶ W/cm²), the role of fragmentation processes either by dissociative ionization or by neutral dissociation is discussed. As an example, the results using laser postionization are employed to quantitatively determine the abundance of Ag₂ molecules in the flux of neutral particles sputtered from the silver sample.     

Silver isotopes produced by alpha-particles on rhodium

Excitation functions for the production of^105(m+g)Ag^106(m)Ag, from (,xn) reactions on natural Rhodium were determined experimentally in this paper. The method of activation of stacked metallic foils was employed. The irradiations were performed in the Isochronous Cyclotron at Karlsruhe (IK III/Zyclotron, Germany) with -particles at 87 MeV. Gamma-spectrometry by with an intrinsic Ge detector was used to determine the produced nuclides. In addition, the yields of thick targets were calculated. In order to compare all the reactions (,xn) (x=1–4) on rhodium we used data from a previous work made at the Cyclotron in Buenos Aires, where the excitation functions for the production of¹⁰³Rh(,xn)^107–x Ag(x=1–4) were determinated. A comparison between the experimental and the cross sections calculated using the EXCLUSIVE INDEX model is presented.     

Zur Multi-Elementanreicherung aus eisenhaltigen B?den und Sedimenten

Summary Traces of Ag, Bi, Cd, Co, Cu, Hg, In, Mo, Ni, Pb, Se, and Zn can be preconcentrated with recoveries R_s 95% from soils and sediments of high iron content by collector precipitation with hexamethylene-ammonium-hexamethylenedithiocarbamate and with a small amount of the iron as a collector element. The trace concentrates are analyzed by AAS and XRF. The relative standard deviation of the combined method of sample decomposition, preconcentration and AAS determination (n = 12) is generally about 0.03; the limit of detection (3 s, n = 20) for different elements was found to be between 0.1 and 1 g·g^–1. The accuracy of the method was verified by certified standard material. The power of detection of XRF for the analysis of trace concentrates obtained from soils and sediments is only sufficient for some of the interesting elements.     

The distribution coefficient of60Co in sediments from the Solway Firth, UK

The behaviour of⁶⁰Co in sea water and sediments typical of the Solway Firth has been investigated. The distribution coefficient,K _d, of⁶⁰Co²⁺ in sediments was determined using the batch sorption method and theK _d variation with aqueous phase composition, sediment type and pH has been studied. Adsorption of⁶⁰Co by sediments was found to be highest in de-ionised water and lower in NaCl solution (31 salinity). Adsorption was lowest in natural sea water, where theK _d range was 2,270 to 2,750. Variation ofK _d with sediment grain size was observed. It was shown that⁶⁰Co adsorption was strongly dependent on pH in de-ionised water, with less variation in NaCl solution. Variance of⁶⁰CoK _d values were lowest in sea water in the range pH 5–8 indicating a more conservative behaviour of⁶⁰Co than previously recognised. Hence⁶⁰Co dispersion will be predominantly govemed by tidal behaviour.     

Study of the kinetics of the transport of Cu(II), Cd(II) and Ni(II) ions through a liquid membrane

The coupled transport of Cu(II), Cd(II) and Ni(II) ions through a bulk liquid membrane (BLM) containing pyridine-2-acetaldehyde benzoylhydrazone (2-APBH) as carrier dissolved in toluene has been studied. Once the optimal conditions of extraction of each metal were established, a comparative study of the transport kinetics for these metals was performed by means of a kinetic model involving two consecutive irreversible first-order reactions. The kinetic parameters (apparent rate constants of the metal extraction and re-extraction reactions (k ₁, k ₂), the maximum reduced concentration of the metal in the liquid membrane (), the time of the maximum value of R _o ( t _max) and the maximum entry and exit fluxes of the metal through the liquid membrane ( and ) of the extraction and stripping reactions were evaluated and results showed good agreement between experimental data and theoretical predictions. Complete transport through the membrane took place according to the following order: Cd(II)>Cu(II)>Ni(II), with similar kinetic parameters obtained for Cu(II) and Cd(III). The transport behaviour of Ni(II) was different to that of Cu(II) and Cd(III), probably due to the different stoichiometry of the nickel complex compared to those of the other metal ions and the different chemical conditions required for its formation. The influence of the sample salinity on the transport kinetics was studied. k ₁ values decreased slightly when the feed solution salinity was increased for Cu(II) and Ni(II), but not for Cd(II). Values of k ₂ were practically unaffected. The proposed BLM was applied to the preconcentration and separation of metal ions (prior to their determination) in water samples with different saline matrices (CRM, river water and seawater), and good agreement with the certified values was obtained.