Qualitative analysis of gold plating by the Ring Oven technique

Summary Gold plating was sampled by anodic dissolution in brominated hydrochloric acid, and the metals were then separated by a modifiedWeisz Ring Oven scheme. In, Fe, Ni, Co and Cr appeared in Ring I; Ag was complexed as the bromide and separated with Cu in Ring II; Au was separated in Ring III by a modified washing scheme. Various colour reactions were then applied for the detection of the metals in the Rings, and in general the limits of detection were 0.1 g.

---

Zusammenfassung Goldplattierungen wurden in bromhältiger Salzsäure anodisch gelöst und die Metalle nach einer modifizierten Ringofentechnik getrennt. In, Fe, Ni, Co und Cr gehen in den 1. Ring; Ag wird als Bromid gebunden und geht mit Cu in den 2. Ring, Au wird dann durch ein modifiziertes Auswaschverfahren in den 3. Ring gebracht. Verschiedene Farbreaktionen dienten zum Nachweis der Metalle. Die Nachweisgrenze lag im allgemeinen bei 0,1 g.

---

Résumé On a effectué le prélévement du revêtement d'or par dissolution anodique dans l'acide chlorhydrique bromé et l'on a séparé ensuite les métaux sur le four annulaire deWeisz, suivant un mode opératoire modifié. In, Fe, Ni, Co et Cr sont apparus sur l'anneau I; Ag a été complexé á l'état de bromure et séparé avec Cu sur l'anneau II; Au a été séparé sur l'anneau III suivant un procédé de lavage modifié. On a alors fait appel á des réactions donnant des couleurs différentes pour déceler les métaux sur les anneaux et les limites de dilution étaient en général de 0,1 g.

     

Chromatographic separation by a new chelating resin containing β-hydroxydithiocinnamic acid

Summary The distribution coefficients of Ag(I), Au(III), Cd(II), Cu(II), Fe(III), Hg(II), Ni(II), Pb(II), Pt(IV), and Zn(II) on a new chelating resin containing -hydroxydithiocinnamic acid at various acidity were studied. In the strongly acidic region, the resin shows high affinity for Ag(I), Hg(II), Au(III) and Pt(IV) and high resistance against air oxidation. The effect of diverse foreign ligands on the sorption of metal ions and the possibility of application to speciation studies with this resin were also considered. Some quantitative separations of Cd-Cu-Pb, Cu-Au and Au-Pt with this resin column were described. Detection of the chromatography system was carried out via post column derivatisation of the column effluent with PAR at 520 nm or direct UV detection of the chloride complexes at 215 nm.     

Determination of Gold, Silver, and Copper in Gold-Base Alloys by Potentiostatic Coulometry

The working conditions for the simultaneous coulometric determination of 0.5 to 3 mg of gold, silver, and copper with a relative standard deviation of at most 0.5% were found in the study of the voltammetric behavior of Au(III), Ag(I), and Cu(II) at a platinum electrode in a 2 M HCl + 0.1 M KCNS solution. Fivefold mass amounts of gold with respect to silver and copper did not interfere with their determination. The three elements can be triply determined in a single portion of a solution using the alternate cathodic and anodic polarization of the electrode ensuring the complete deposition and stripping of Au(0) and Ag(0) and the complete reduction and oxidation of Cu(II) Cu(I). The mechanism of current formation due to the chemical reaction of Au(I) disproportionation and its effect on the results of gold determination were studied using the current–time curves. Experimental conditions were proposed to eliminate this reaction. The procedure was used for determining the composition of ternary jewelry alloys containing different amounts of gold, silver, and copper without their preliminary separation.     

Zweij?hrige Erfahrung in der Routineanalyse mit einem C-N-H-Automaten

Zusammenfassung Unsere Erfahrungen bei der Routineanalyse von festen und flüssigen Verbindungen, die z.B. D, F, Cl, Br, J, S, Se, Cr, W, P, Bi, Si, Sn, Pb, Ti, B, Hg, Na, K, Cu, Ag, Au, Fe oder Ni enthalten, mit einem Automaten, der in einem. 10 min-Cyclus die Prozentgehalte von C, N und H. ausdruckt, werden mitgeteilt.

---

Summary This paper communicates our experiences in routine analyses of solid and liquid compounds, containing elements such as D, F, Cl, Br, J, S, Se, Cr, W, P, Bi, Si, Sn, Pb, Ti, B, Hg, Na, K, Cu, Ag, Au, Fe or Ni with an automatic instrument which prints out the percentages of C, N and H within 10 minutes.

---

---

Die angegebenen Werte stellen den Standardfehler dar.     

“Multitracer” a new tracer technique — Its principle,features, and application

We established Multitracer, a new versatile radiotracer technique, for simultaneous tracing of a number of elements in various chemical, environmental, and biological systems. Metal foil targets (typically Au, Ag, Ge, Cu and Fe) are irradiated with C, N, or O ions accelerated up to 135 MeV/nucleon by RIKEN Ring Cyclotron. Radiochemical procedures have been developed to remove the target material leaving the nuclides as Multitracer solutions containing various radionuclides of Be, Na, Mg, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Te, I, Ba, Ce, Pm, Eu, Gd, Tb, Tm, Yb, Lu, Hf, W, Re, Os, Ir, Pt, and Hg. Multitracers enable efficient tracing of a number of elements, and comparison of their behavior under strictly identical experimental conditions. Such features will be demonstrated by means of an example of application to a model experiment for the study of removal mechanism of various elements from the ocean.     

Static investigation of adsorption and hetero‐diffusion of copper,silver, and gold adatoms on the (111) surface

In this work, we have used the static molecular simulations combined with an interatomic potential derived from the embedded‐atom method to study the adsorption and hetero‐diffusion on the (111) surface of Cu, Ag, and Au adatoms by using LAMMPS code. The investigation is performed for six heterogeneous systems such as Ag/Au(111), Ag/Cu(111), Au/Ag(111), Au/Cu(111), Cu/Ag(111), and Cu/Au(111). First, we have investigated the relaxation trends and the bond lengths of the atoms in the systems. The calculation results show that, the top layer spacing between the first and second layers of the Au(111), Ag(111), and Cu(111) substrates is contracted. This contraction is found to be more important in the Au(111) substrate. On the other hand, the strong reduction of the binding length is found in Au/Cu(111) for the different adsorption sites. In addition, the binding, adsorption, and static activation energies for all studied systems were examined. The results indicated that the binding and adsorption energies reached their maximum values in the Au/Cu(111) and Au/Ag(111) systems, respectively. Moreover, the static activation barriers for hopping diffusion on the (111) surfaces are found to be low compared with those found in the (100) and (110) surfaces. Therefore, our calculations showed that the difference in energy between the hcp and fcc sites on the (111) surfaces is very small. Copyright © 2017 John Wiley & Sons, Ltd.     

Nanoporous ultra-high-entropy alloys containing fourteen elements for water splitting electrocatalysis

High-entropy alloys (HEAs) are near-equimolar alloys comprising five or more elements. In recent years, catalysis using HEAs has attracted considerable attention across various fields. Herein, we demonstrate the facile synthesis of nanoporous ultra-high-entropy alloys (np-UHEAs) with hierarchical porosity via dealloying. These np-UHEAs contain up to 14 elements, namely, Al, Ag, Au, Co, Cu, Fe, Ir, Mo, Ni, Pd, Pt, Rh, Ru, and Ti. Furthermore, they exhibit high catalytic activities and electrochemical stabilities in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in acidic media, superior to that of commercial Pt/graphene and IrO₂ catalysts. Our results offer valuable insights for the selection of elements as catalysts for various applications.

Nanoporous ultra-high-entropy alloys containing 14 elements (Al, Ag, Au, Co, Cu, Fe, Ir, Mo, Ni, Pd, Pt, Rh, Ru, and Ti) were obtained by dealloying. The products showed excellent electrocatalytic performance for water splitting in acidic media.     

Study of hair element content from an urban Bulgarian population using NAA assessment of environmental status

In this preliminary study, scalp hair samples from 36 individuals resident in Sofia, Bulgaria, were analysed and Ag, Al, As, Au, Ba, Br, Ca, Cd, Ce, Cl, Co, Cr, Cs, Cu, F, Fe, Hg, I, K, La, Mg, Mn, Mo, Na, Ni, Rb, S, Sb, Sc, Se, Sn, Sr, Ti, V, W, and Zn were determined. Instrumental neutron activation analysis (INAA) methods were used. Three washing procedures.: distilled-deionised water; acidacetone-water; and Triton X-100 detergent-water, showed a variable elemental change strongly dependent on the procedure used. More than 18 elements (Al, As, Ba, Ca, Ce, Cl, Co, Cs, F, Fe, I, K, La, Mo, Na, Ni, Sb, Sc, Sr and V) were easily removed by water-washing. Triton X-100 detergent was more effective in removing Ag, As, Au, Cl, Cs, K, Na and Rb; but not Hg. Only S and Zn were strongly incorporated in the hair structure (less than 10% being removable by any washing technique). There is no significant age correlation with any element between the various hair treatment groups. Elevated cadmium levels were found in the hair of smokers (0.711–4.913 g/g Cd) compared with nonsmokers (0.568–2.681 g/g Cd). Comparison of the elemental data for distilled water-washed hair and studies from Oxford, England and Hastings, and Hastings, New Zealand (using the same INAA method) revealed interesting variations dependent on local industrial and nutritional factors.     

Synthesis of p-aminothiophenol-embedded gold/silver core-shell nanostructures as novel SERS tags for biosensing applications

We describe a novel surface-enhanced Raman scattering (SERS) tag that is based on Au/Ag core-shell nanostructures embedded with p-aminothiophenol. The Au/Ag core-shell sandwich nanostructures demonstrate bright and dark stripe structure and possess very strong SERS activity. Under optimum conditions, the maximum SERS signal was obtained with a 10?nm thick Ag nanoshell, and the enhancement factor is 3.4?×?10⁴ at 1077?cm^?1. After conjugation to the antibody of muramidase releasing protein (MRP), the Au/Ag core-shell nanostructures were successfully applied to an SERS-based detection scheme for MRP based on a sandwich type of immunoassay.

Application of factor analysis and simplex technique to the optimization of a phosphate determination via molybdenum blue

Zusammenfassung Aus Reinst-Cadmium können durch partielles Lösen der Matrix die Elementspuren Ag, Au, Bi, Co, Cu, Fe, In, Ni, Pb, Pd und Sn angereichert werden. Dazu werden die Proben mit einem dünnen Quecksilberfilm überzogen und in Bromwasserstoffsäure bis auf einen kleinen Rest gelöst. Die im Löserückstand angereicherten Spuren werden durch Atomabsorptions-Spektrometrie bestimmt. Die relativen Standardabweichungen betragen etwa 0,05; die Anreicherungsausbeuten sind > 95%. Bei Einwaagen von 10 g Cadmium beträgt der Anreicherungsfaktor etwa 10²; die Nachweisgrenzen (3-Grenzen) liegen um 0,1 ppm. Der Einfluß der Lösebedingungen auf die Anreicherung wird diskutiert.

---

Determination of trace elements in high-purity cadmium by AAS after preconcentration by partial dissolution of the matrix

Trace elements such as Ag, Au, Bi, Co, Cu, Fe, In, Ni, Pb, Pd, and Sn can be preconcentrated from high-purity cadmium by partial dissolution of the matrix. The samples are coated by a thin film of mercury and dissolved in hydrobromic acid up to a small residue. In this residue the trace elements are enriched with recoveries of more than 95%. The elements are determined by AAS. For 10 g Cd the factor of enrichment is about 10², and the limits of detection are in the range of 0.1 ppm. The relative standard deviation was calculated to be about 5%. Reasons influencing the recovery of the trace elements are discussed.

     

Synthesis and characterization of silica gel microspheres encapsulated by salicyclic acid functionalized polystyrene and its adsorption of transition metal ions from aqueous solutions

The present study was undertaken to develop a novel adsorbent for heavy metal ions, and this paper presents the synthesis and characterization of a composite material-silica gel microspheres encapsulated by salicyclic acid functionalized polystyrene (SG-PS-azo-SA) with a core-shell structure. SG-PS-azo-SA was used to investigate the adsorption of Mn(II), Co(II), Ni(II), Fe(III), Hg(II), Zn(II), Cd(II), Cr(VI), Pd(II), Cu(II), Ag(I), and Au(III) from aqueous solutions. The results revealed that SG-PS-azo-SA has better adsorption capacity for Cu(II), Ag(I) and Au(III). Langmuir and Freundlich isotherm models were applied to analyze the experimental data, the best interpretation for the experimental data was given by the Langmuir isotherm equation with the maximum adsorption capacity for Cu(II), Ag(I), and Au(III) at 1.288 mmol g⁻¹, 1.850 mmol g⁻¹ and 1.613 mmol g^t-1, respectively. Thus, silica gel encapsulated by salicyclic acid functionalized polystyrene (SG-PS-azo-SA) is favorable and useful for the removal of Cu(II), Ag(I) and Au(III) metal ions.     

Preconcentration of trace elements by partial dissolution of the matrix—multielement preconcentration from manganese

Trace elements such as Ag, Au, Bi, Cd, Co, Cu, Fe, Ga, In, Ni, Pb, Pd and Tl, can be preconcentrated with recoveries of better than 95% from high-purity manganese if the sample is coated with a thin layer of mercury before its dissolution in HCl to a small residue. For determination of the trace elements, the residue is completely dissolved in aqua regia. After separation of the mercury by reductive precipitation, Bi, Cd, Co, Cu, Fe, Ga, In, Ni, Pb, and Tl are determined by flame a.a.s. ('injection method'). Ag, Au and Pd are determined in the mercury-containing solution. The relative standard deviation was usually about 5%; Cu, Fe and Pb were proved to be inhomogeneously distributed in the sample (electrolytically produced manganese), and so the standard deviations were considerably greater. The detection limits for the different elements were between 0.6 and 0.004 ppm, depending on the sensitivity of their a.a.s. determination. The theoretical basis of this preconcentration method and its applicability to multielement analysis of different high-purity metals are discussed.     

Anwendung der Streustrahl-Methode zur Bestimmung der Elemente in Mineral?lprodukten mit Hilfe der R?ntgenfluorescenz-Spektral-Analyse am Beispiel der Bleibestimmung in Ottokraftstoffen

Zusammenfassung In einem relativ einfach durchzuführenden Verbundverfahren wird Selen im Sauerstoff-strom innerhalb 15 min bei 1100–1150°C quantitativ aus den Metall- bzw. Metalloxidschmelzen verdampft und in einer mit flüssigem Stickstoff gekühlten Vorlage aufgefangen. Das aus der Vorlage mit einer definierten Menge verdünnter HNO₃ in Gegenwart von Ni-Nitrat gelöste Selen läßt sich direkt durch AAS mit dem Graphitofen (FAAS) äußerst nachweisstark und zuverlässig bestimmen. Die Nachweisgrenze (elektrodenlose Entladungslampe) liegt bei 3×10^–11 g Se. Der Verfahrensverbund erlaubt mit Probenmengen 10 g in Ag und Au Se-Gehalte 0,05 ppb,inCu 0,1 ppb,in Bi 0,2 ppb und in Pb 10 ppb zu erfassen. Für draht-, stab- und spanförmige Proben erhält man für Se-Gehalte von 2–0,002 ppm Variationskoeffizienten zwischen 3 und 6%. Die Vollständigkeit der Se-Verdampfung aus den Matrices Cu, Ag, Au und Bi wurde ebenso wie die Richtigkeit des Gesamtverfahrens durch systematische Untersuchungen belegt.

---

Determination of se by furnace atomic absorption spectrometry (FAAS) in the ppb-range in Cu, Cu alloys, Ag, Au, Pb and Bi after volatilization in an oxygen stream

Summary Selenium is evaporated in a multi-stage procedure within 15 min from metals or metal oxides fused at temperatures of 1100–1150°C under a stream of oxygen and is trapped in a receiver cooled with liquid nitrogen. The condensed SeO₂ is dissolved with a definite volume of diluted HNO₃ in the presence of Ni-nitrate and determined with high sensitivity and reliability by FAAS (electrodeless discharge lamp). The detection limit of the FAAS was found to be 3 · 10^–11 g of Se. The multi-stage procedure allows to detect Se levels 0.05 ppb in Ag and Au, 0.1 ppb in Cu, 0.2 ppb in Bi, and 10 ppb in Pb, respectively, with sample weights 10 g. For wire, rod, and chip samples the coefficients of variation are found to be between 3 and 6% for Se contents of 2 to 0.002 ppm. The quantitative evaporation of Se from Cu, Ag, Au, and Bi as well as the accuracy of the whole procedure have been checked systematically.

Die Arbeit wurde durch Mittel der DFG in dankenswerter Weise unterstützt.     

Binding Selectivity of Methanobactin from <Emphasis Type="Italic">Methylosinus trichosporium</Emphasis> OB3b for Copper(I), Silver(I), Zinc(II), Nickel(II), Cobalt(II), Manganese(II), Lead(II), and Iron(II)

Methanobactin (Mb) from Methylosinus trichosporium OB3b is a member of a class of metal binding peptides identified in methanotrophic bacteria. Mb will selectively bind and reduce Cu(II) to Cu(I), and is thought to mediate the acquisition of the copper cofactor for the enzyme methane monooxygenase. These copper chelating properties of Mb make it potentially useful as a chelating agent for treatment of diseases where copper plays a role including Wilson’s disease, cancers, and neurodegenerative diseases. Utilizing traveling wave ion mobility-mass spectrometry (TWIMS), the competition for the Mb copper binding site from Ag(I), Pb(II), Co(II), Fe(II), Mn(II), Ni(II), and Zn(II) has been determined by a series of metal ion titrations, pH titrations, and metal ion displacement titrations. The TWIMS analyses allowed for the explicit identification and quantification of all the individual Mb species present during the titrations and measured their collision cross-sections and collision-induced dissociation patterns. The results showed Ag(I) and Ni(II) could irreversibly bind to Mb and not be effectively displaced by Cu(I), whereas Ag(I) could also partially displace Cu(I) from the Mb complex. At pH ≈ 6.5, the Mb binding selectivity follows the order Ag(I)≈Cu(I)>Ni(II)≈Zn(II)>Co(II)>>Mn(II)≈Pb(II)>Fe(II), and at pH 7.5 to 10.4 the order is Ag(I)>Cu(I)>Ni(II)>Co(II)>Zn(II)>Mn(II)≈Pb(II)>Fe(II). Breakdown curves of the disulfide reduced Cu(I) and Ag(I) complexes showed a correlation existed between their relative stability and their compact folded structure indicated by their CCS. Fluorescence spectroscopy, which allowed the determination of the binding constant, compared well with the TWIMS analyses, with the exception of the Ni(II) complex.

Open image in new window

Graphical abstract ?

     

Anreicherung von Spuren Ag, Au, Bi, Cu und Pd aus Feinblei durch reduktives Anf?llen der Matrix mit Natriumboranat

Zusammenfassung Gruppen von Elementspuren können aus unterschiedlichen Probenmaterialien quantitativ angereichert werden, wenn man einen geringen Anteil der Matrix durch Zusatz von NaBH₄ reduktiv ausfällt. Der metallische Niederschlag wirkt dabei als Spurenfänger für alle Elemente, die elektrochemisch edler sind als die Matrix. Als Beispiel für diese Anreicherungstechnik wurden Spuren Ag, Au, Bi, Cu und Pd aus Proben von 10 g Feinblei angereichert und nach Auflösen des Spurenfängers in Säure durch Flammen-Atomabsorptions-Spektrometrie bestimmt. Bei Spurengehalten von wenigen g/g werden rel. Standardabweichungen um 5 % erzielt; die Nachweisgrenzen liegen — je nach Element — zwischen 0,05 und 0,4 g/g. Die Richtigkeit des Analysenverfahrens wurde anhand analysierten Probenmaterials sichergestellt.

---

Preconcentration of traces of Ag, Au, Bi, Cu, and Pd, from pure lead by partial precipitation of the matrix with NaBH₄ as a reducing agent

Summary Selected groups of trace elements can be preconcentrated from different materials by precipitation of a small amount of the matrix with NaBH₄ as a reducing agent. The metallic precipitate serves as a trace collector for all elements being electrochemically nobler than the matrix. As an example for this technique traces of Ag, Au, Bi, Cu, and Pd are enriched from samples of 10 g pure lead and, after dissolving the collector in acid, determined by flame atomic absorption spectrometry. With trace contents of a few g/g relative standard deviations of about 5 % are achieved. Depending on the element, the limit of detection was found to be between 0.05 and 0.4 g/g. The accuracy of the analytical procedure was verified by use of analysed reference samples.

Wir danken der Deutschen Forschungsgemeinschaft für die Unterstützung mit Personal- und Sachmitteln.     

Structure and Electron Transport at Metal Atomic Junctions Doped with Dichloroethylene

We have investigated the structure and electron transport at dichloroethylene-doped metal atomic junctions at low temperatures (20 K) in ultra-high vacuum, using Fe, Ni, Pd, Cu, Ag, and Au. The metal atomic junctions were fabricated using the mechanically controllable break junction technique. After introducing the dichloroethylene (DCE), the conductance behavior of Fe, Ni, and Pd junctions was considerably changed, whereas little change was observed for Cu, Ag, and Au. For the Pd and Cu junctions, a clear peak was observed in their conductance histograms, showing that the single-molecule junction was selectively formed. To investigate the structure of the metal atomic junctions further, their plateau lengths were analyzed. The length analysis revealed that the Au atomic wire was elongated, and the metal atomic wires were formed for the other transition metals: those that do not normally form metal atomic wires without DCE doping, as DCE adsorption stabilized the metal atomic states. There is a strong interaction between DCE and the metals, where DCE supports the formation of the metal atomic wire for Fe, Ni, and Pd.     

Determination of detection limits in graphite furnace atomic absorption spectrometry by using ensemble summation of signals

Summary The detection limits of Ag, As, Au, Bi, Cd, Cr, Fe, Mn, Ni, P, Pb, Sb, Se and Te in the presence of 50 g of copper are determined by Zeeman graphite furnace atomic absorption spectrometry (Zeeman/GFAAS) using the method of ensemble summation. Processing of atomic absorption signals of masses close to the detection limits is illustrated.

---

Bestimmung von Nachweisgrenzen in der Graphitofen-Atomabsorptionsspektrometrie durch Anwendung der Ensemblesummierung von Signalen

Zusammenfassung Die Nachweisgrenzen von Ag, As, Au, Bi, Cd, Cr, Fe, Mn, Ni, P, Pb, Sb, Se und Te in Anwesenheit von 50 g Kupfer wurden mit Hilfe der Zeeman Graphitofen-Atomabsorptionsspektrometrie (Zeeman/GAAS) unter Anwendung der Ensemblesummierung bestimmt. Diese ermöglicht die Bearbeitung der Atomabsorptions-Signale von Massen in der Nähe der entsprechenden Nachweisgrenzen.

     

Multi-element preconcentration from technical alkali silicates

Summary After evaporation of the matrix SiO₂ as SiF₄ traces of Ag, Au, Bi, Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, Pd, Sn, Tl, V and Zn can be preconcentrated from water glasses with recoveries R_s 95% by collector precipitation with hexamethyleneammonium - hexamethylenedithiocarbamate and indium as collector element (Se and Te with varying recoveries between 90 and 95%). The relative standard deviation of the combined method of sample decomposition, preconcentration and AAS-determination is generally about 5% (n=17); the detection limits were found to be between 0.01 and 2 g·g^–1 (3s, n=24). The accuracy of the determination step was verified by analysing the trace concentrates by AAS, ICP-OES and TR-XFS.     

Interaction of SO2 with single crystal metal surfaces

Studying the interaction of SO₂ with metal surfaces under UHV conditions, a question of central interest is whether the molecule dissociates (leaving back the catalyst poison sulphur on the surface) or not. A spontaneous or a thermally activated dissociation of SO₂ occurs on Fe, Rh, W, Ni, Pd and Pt. On Cu and Ag a strong chemisorption, but only a partial dissociation induced by defects or coadsorbed alkalis, and on Au no chemisorption at all were observed.

In this paper a comparison of our results obtained for the chemisorption and multilayer adsorption of SO₂ on Cu(111), Ag(111), Ag(100) and Ag(110) in the temperature range between 80 K and 900 K is given. By combining highly resolved TPD-measurements, isothermal and temperature-programmed ΔΦ-experiments after different stages of exposure and molecular beam backscattering measurements (MBBS) —assisted by LEED, AES and isotope mixing experiments — a destinction between ordinary desorption and desorption after a reorientation process during the heating procedure could be made. Whereas on clean Ag surfaces adsorption and desorption of SO₂ are observed only below 300 K, on Cs-precovered Ag desorption of SO₂ takes place even above 600 K.

Finally, results concerning the different stages of SO₂ multilayer adsorption (bi-, tri-, multilayers) are presented showing a characteristic dependence of the layer growth on the adsorption temperature, the impinging SO₂ flux density and on the surface structure.