Chemical analysis of copper and brass samples from Christian Island,Georgian Bay,Ontario

One hundred and eighty-seven metal samples, recovered from the fortified mission of Ste. Marie II and nearby villages on Christian Island, include 3 samples of native copper, 22 samples of European copper, 19 samples of brassy copper (8% Zn), 141 brass samples and 2 samples of lead. The European copper samples form 5 distinct chemical groups, possibly coming from 5 different copper kettles. The brassy copper samples are more difficult to group. When the brass samples are sorted by Ag and As, they form 2 major groupings: group 1 with high Ag and low As contents; group 2 with similar Ag and As contents through to low Ag and high As contents. Group 1 consisted of 11 chemical sub-groups and 6 outliers, while group 2 contributed 14 sub-groups and 14 outliers. This combines to give a total of 45 potentially unrelated brass chemistries, and leads to the possibility of as few as 20 different brass trading items (mainly kettles) from which the samples were cut. The small sub-sets of samples from the sites away from Ste. Marie II tended to fit within chemical groups found there, suggesting some possible inter-site contemporaneity.     

PIXE analysis of prehistoric and protohistoric Caborn-Welborn phase copper artifacts from the lower Ohio River Valley

Particle-induced X-ray emission (PIXE) spectrometry is being used to nondestructively determine the elemental composition of copper-based artifacts excavated from prehistoric/protohistoric sites in the Ohio River Valley. Copper objects from Caborn-Welborn (C-W) and contemporary Fort Ancient sites are being studied so as to differentiate between native American and European copper. The trace element analysis of metal artifacts enables archaeologists to more accurately assess the material culture and chronological development of C-W society (A.D. 1400–1700) with particular reference to geological sources of copper and brass.     

Instrumental neutron activation analysis of native copper: Some methodological considerations

A scheme for INAA of native copper, which permits the determination of 22–24 elements is proposed. The possible error source in INAA of native copper and other types of more or less pure copper are evaluated quantitatively. The accuracy and precision of the analyses are tested by comparison with NIST-SRM's. The applicability of the proposed method for archaeometric investigations is demonstrated by the analysis of two samples of native copper and two eneolithic archaeological artifacts from Bulgaria.     

Analysis of ancient copper alloys using epithermal activation techniques

A method was developed for the analysis of ancient copper alloys. Over the past three years this method has been applied to a wide range of alloy types, ranging from nominally pure 5th millenium BC coppers to 9th century silver—brass stycas from Northumbria. The analysis of samples provides more analytical information than alternative non-desctructive or non sampling techniques.     

Simultaneous determination of trace-levels of alloying zinc and copper by semi-mercury-free potentiometric stripping analysis with chemometric data treatment

Assays of copper and zinc in brass samples were performed by semi-mercury free potentiometric stripping analysis (S-MF PSA) using a thin-film mercury covered glassy-carbon working electrode and dissolved oxygen as oxidizing agent during the stripping step. The stripping peak transients were resolved by chemometrics, which enabled simultaneous determination of both the copper and the zinc concentrations, thereby eliminating the conventional necessary pretreatment of the sample solution, such as initial addition of Ga(III) or solvent extraction of copper. The brass samples were diluted by factors in the range 2 · 10⁴– 5 · 10⁵ which resulted in quantification of the copper and of zinc contents comparable to the specified values within 10%. On the basis of the chemometric treatment, an empirical expression is deduced relating the stripping time to the recorded potential.     

Simultaneous determination of trace-levels of alloying zinc and copper by semi-mercury-free potentiometric stripping analysis with chemometric data treatment

Assays of copper and zinc in brass samples were performed by semi-mercury free potentiometric stripping analysis (S-MF PSA) using a thin-film mercury covered glassy-carbon working electrode and dissolved oxygen as oxidizing agent during the stripping step. The stripping peak transients were resolved by chemometrics, which enabled simultaneous determination of both the copper and the zinc concentrations, thereby eliminating the conventional necessary pretreatment of the sample solution, such as initial addition of Ga(III) or solvent extraction of copper. The brass samples were diluted by factors in the range 2 · 10⁴– 5 · 10⁵ which resulted in quantification of the copper and of zinc contents comparable to the specified values within 10%. On the basis of the chemometric treatment, an empirical expression is deduced relating the stripping time to the recorded potential. Received: 23 December 1997 / Revised: 25 February 1998 / Accepted: 28 February 1998     

Electrochemical studies on the corrosion of brass in seawater under anaerobic conditions

This paper reports an electrochemical study on the corrosion of brass in deoxygenated nonbuffered and buffered natural and artificial seawater solutions under anaerobic conditions. Cyclic voltammograms of brass and copper in natural seawater (NSW) and artificial seawater (ASW) were obtained in the passive and transpassive potential regions. The corrosion resistance of brass in natural and artificial seawater was evaluated, and open-circuit potentials were recorded over exposure period of 1 week. Brass samples from 3-month exposures in deoxygenated nonbuffered ASW and NSW, under open-circuit potential, have been imaged by scanning electron microscopy, and the elemental composition of the corrosion products was obtained by energy dispersive spectrometry analysis. It has been concluded that, under anaerobic conditions, the aggressivity of NSW is higher, with brass being less resistant to corrosion than copper, and that buffer contributes to reduce the aggressivity of both media.     

Instrumental neutron activation analysis of manganese,copper and vanadium in some commercial steel samples and of copper in copper base alloys

The instrumental neutron activation analysis (INAA) of industrially important steel samples, viz. IS-226, IS-2002, IS-2062, SS-304, SS-310, SS-316 and of copper base alloys, viz. high brass, gun metal and copper-silver alloys is carried out with a 2 Ci²⁵²Cf neutron source. The copper and vanadium content of all the steel samples and manganese content of former three steel samples are estimated by measuring the gamma activity of⁶⁶Cu,⁵²V and⁵⁶Mn radioisotopes, respectively, using a high purity germanium (HPGe) detector coupled to a 4 K multichannel analyzer (MCA). Similarly, the copper content of copper base alloys was also determined.Dedicated to Prof. H. J. Arnikar, Professor Emeritus, University of Poona, on the occasion of his 75th birthday.     

Letters from China: A History of the Origins of the Chemical Analysis of Ceramics

This paper is an attempt to document the early history of the quantitative chemical analysis of ceramic materials in Europe, with a specific interest in the analysis of archaeological ceramics. This inevitably leads to a study of the attempts made in Europe to imitate the miraculous material—porcelain—imported from China from the fourteenth century onwards. It is clear that before the end of the eighteenth century progress was made in this endeavour by systematic but essentially trial-and-error firing of various raw materials, culminating in the successful production of European porcelain by Böttger and von Tschirnhaus in 1709. Shortly after this, letters describing the Chinese manufacture of porcelain, and, more importantly, samples of raw and fired material, began to arrive in Europe from French Jesuit missionaries, which were subjected to intense study. Following the perfection of gravimetric methods of chemical analysis in the late eighteenth century, these Chinese samples, and samples of porcelain from various European factories, were regularly analysed, particularly by Brongniart at Sèvres. Similar work was carried out on English porcelain by Simeon Shaw and Sir Arthur Church. The origins of the chemical analysis of archaeological ceramics are still somewhat obscure, but must date to the late eighteenth or early nineteenth centuries, by the likes of Vauquelin and Chaptal.     

Electropolymerization of Mefenamic Acid on Copper and Copper Based Alloy as a New Strategy to Control the Release of Copper Ions from Copper Containing Devices

Poly-2-(2,3-dimethylanilino) benzoic acid (PMF) coatings on copper and brass alloy were synthesized by electrochemical oxidation of 2-(2,3-dimethylanilino) benzoic acid in the presence of oxalic acid as the reaction medium. Electrodeposition was carried out using the cyclic voltammetry technique using a silver/silver-chloride standard electrode, with a scan rate of 600 mV min^–1. Smooth and well adhered PMF coatings were electrosynthesized during sequential scanning of the potential in the range–500 mV to 1400 mV on copper and brass alloy. The electrodeposited coatings were characterized by recording the oxidation peaks at 122 mV for Cu and–0.7 mV for brass, in cyclic voltammetry and using scanning electron microscopy (SEM). Corrosion inhibition efficiency of coated copper and brass alloy was investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The impedance results showed that the inhibition efficiency of coated copper is 89% and for coated brass 79.4% compared to the uncoated copper and brass in 0.1 M H₂SO₄.

     

Bronze analysis by k0-NAA and PIXE

Five copper alloys were prepared with modern powder metallurgical processes in the frame of the European project Improvement of Means of Measurement on Archaeological Copper-Alloys for Characterisation and Conservation (IMMACO) and certified for As, Pb, Sn and Zn mass fractions. Similar in their composition to archaeological bronze alloys, these Certified Reference Materials (CRMs) are to be used for calibration of XRF instruments for characterization of archaeological samples either in the laboratory or in the field. This paper presents and compares the successful contribution of our non-destructive analytical methods (k ₀-NAA and PIXE) to the IMMACO project and to the certification of the five reference materials.     

Multi-instrumental analysis of asphalts of archaeological interest

Use was made of thermal and other techniques to characterise three native asphalt samples. The purpose was to support archaeological investigations reconstructing their thermal history and composition. The first sample (from a Roman quarry in central Italy) proved to have 37% impurities, no sign of oxidation or degradation and to have never been heated to above 100°C. The second sample (from a Roman ship sunk south of France) was pure, but partially oxidised, with a saturated fraction in its structure. Analyses of the latter sample, obtained from the eye of a Thracian bronze head, revealed that the asphalt had been heated to over 100°C and then mixed with natural wax.     

Characterisation of archaeological waterlogged wood by pyrolytic and mass spectrometric techniques

Two techniques based on analytical pyrolysis and mass spectrometry, direct exposure-MS (DE-MS) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), were used to characterise waterlogged archaeological wood and to study degradation patterns of wood in aqueous environments. The two techniques were applied to samples from the excavation of the Site of the Ancient Ships of Pisa San Rossore in Pisa (Italy), and data were compared to those relative to native sound wood of the same species (pine, elm, beech). Both the methods result valuable in the analysis of ancient wood artefacts, avoiding the long wet-chemical procedures that are commonly used in wood analysis, and allowing us to use a minimal sample size. DE-MS achieves a global mass spectral fingerprint of lignin and polysaccharides pyrolysis compounds in few minutes, and the results have been interpreted with the support of principal component analysis (PCA) of mass spectra. Py-GC/MS permits detailed molecular analysis of pyrolysis compounds and highlights some chemical modifications of lignin in archaeological samples, as demethylation of both guaiacyl and syringyl lignin units. Both the techniques demonstrate consistent loss of polysaccharides in archaeological wood.     

Investigation of the rubber-metal bonding system by means of analytical electron microscopy and comparison with results of technical tear strength measurements

During vulcanization of sulfur-cure mixtures in contact with brass, a bonding layer consisting of sublayers of copper and zinc sulfides and oxides is formed. As the chemical composition and structure of the layer are decisive for good adhesion. the rubber to brass bonding was investigated using an analytical electron microscope (AEM) coupled with an energy dispersive X-ray (EDX) detector. Sublayers were found in the bonding layer between rubber and brass. Different crystallographic phases were identified in an etched bonding layer by electron diffraction. Technical tear strength measurements were carried out using rubber-brass-rubber samples, showing correlations with the electron microscopic investigations. This method is a new approach to the rubber-metal bonding (adhesion) problem.     

Radioisotope x-ray fluorescence analysis of ancient pottery from Tel Kouzama site in Damascus, Syria

The radioisotope X-ray fluorescence method has been utilized in the analysis of thirty nine archaeological pottery fragment samples from Tel Kouzama site, Damascus city, Syria. The samples were irradiated by a 109Cd radioisotope source (-9 10(8) Bq) for 1000 s. 17 chemical elements were determined. These elemental concentrations have been processed using two multivariate statistical methods, cluster and factor analysis in order to determine similarities and correlation between the various samples. Factor analysis confirms that samples were correctly classified by cluster analysis. These two methods suggest that samples can be considered to be manufactured using four different sources of raw material.     

Characterization of waterlogged wood by NMR and GPC techniques

Anaerobic erosion bacteria can slowly degrade waterlogged wood, causing a loss of cellulose and hemicellulose. During this process, lignin can also be altered. For this reason, the chemical characterization of waterlogged archaeological wood is crucial for both the elucidation of the degradation processes and also the development of consolidation and conservation procedures.The complex structure of wood makes it practically impossible to dissolve wood in its native form in conventional molecular solvents. Ionic liquids can provide a homogeneous reaction medium for wood-based lignocellulosic materials. Highly substituted lignocellulosic esters and phosphite esters can be obtained under mild conditions by reacting pulverized wood dissolved in ionic liquid with either acyl chlorides or dioxaphospholanes in the presence of pyridine. As a result, the functionalized wood develops an enhanced solubility in molecular solvents, allowing for a complete characterization by means of spectroscopic and chromatographic techniques.In this study, archaeological woods and reference sound woods of the same taxa (Quercus and Arbutus unedo), along with the corresponding extracted lignin, were fully characterized by means of phosphorus NMR spectroscopy, two dimensional NMR spectroscopy and GPC analysis. The samples were collected from the Site of the Ancient Ships of San Rossore (Pisa, Italy), where many shipwrecks dating from 2nd century BC to 5th century AD have been discovered.The results highlighted a deeper and faster depolymerization of the polysaccharide matrix against a limited degradation of the lignin fraction. The use of innovative solvent system as the ionic liquid [amim]Cl enables to highlight chemical and morphologic changes in wood composition avoiding further degradation.     

Determination of Copper by Atomic Absorption Spectrophotometry After Solid-Liquid Separation by Adsorption of its 1-Nitroso-2-Naphthol Complex onto Microcrystalline Benzophenone

ABSTRACT

A sensitive method for the determination of trace copper by preconcentration and adsorption of its 1-nitroso-2-naphthol complex onto the microcrystalline benzophenone has been developed. Several experimental conditions such as the pH of the solution, the quantities of 1-nitroso-2-naphthol and benzophenone, and the stirring time were optimized for effective separation. Trace copper in a 100 ml water sample was chelated with 2.0 ml of 0.050 M 1-nitroso-2-naphthol at pH 8.0. The solution was heated to 30 °C, stirred vigorously for 10 minutes to adsorb the copper complex quantitatively onto 0.20 g benzophenone. After the microcrystalline benzophenone adsorbed copper complex was filtered and dissolved in acetone, the content of copper was determined by flame atomic absorption spectrophotometry. The interfering effects of concomitant ions were investigated and almost eliminated. The detection limit and the determination limit of this method were 6.9 ngml^?1 and 22.9 ngml^?1, respectively. Recoveries of 103.7 % and 94.2 % were obtained in a tap water and a brass sample, respectively. In the determination of copper in real samples, the values obtained by this proposed method were close to those by GF-AAS.

Based on these experimental results, it is supposed that this method can be applied to the determination of copper in real samples.     

Electrochemical quantification of copper-based alloys using voltammetry of microparticles: optimization of the experimental conditions

Voltammetry of microparticles has been used in this work for the qualitative and quantitative analyses of zinc, tin, lead and copper in binary, ternary or quaternary alloy samples. The analyses were carried out by spiking small amounts of the metals into a carbon paste electrode, after which they were anodically stripped off using differential pulse voltammetry. The work involved four separate experiments. The first one examined the type of electrolyte, which is suitable to identify the four elements. More specifically, the aim was to examine in which electrolyte all elements can be measured simultaneously–as would be the case in a quaternary copper alloy–without seeing any overlap in their current peaks. The second experiment focused on optimizing the measurement conditions with the aim of having the current peaks of each element well separated from the others. For this part, we made use of the central composite design. The aims were to: (i) maximize the separation between current peaks, (ii) determine which variable has a higher impact on the response, (iii) give an insight in the robustness of the method close to the optimum conditions and (iv) eventually show interactions between variables. In the third experiment, the four elements were quantified in their binary mixtures. Here, the percentage of the oxidation current for each metal, which is directly related to the ratio of the metal in the binary matrices, was employed for the calibration. Finally, in the last experiment, the elements were quantified in two real quaternary samples: a brass and a lead bronze.     

XAS study on copper red in ancient glass beads from Thailand

Glass has been used in ornaments and decorations in Thailand for thousands of years, being discovered in several archeological sites and preserved in museums throughout the country. To date only a few of them have been examined by conventional methods for their compositions and colorations. In this work we report for the first time an advanced structural analysis of Thai ancient glass beads using synchrotron X-ray absorption spectroscopy (XAS) and energy-dispersive X-ray (EDX) spectrometry. Four samples of ancient glass beads were selected from four different archeological sites in three southern provinces (Ranong, Krabi and Pang-nga) of Thailand. Archaeological dating indicated that they were made more than 1,300 years ago. A historically known method for obtaining a red color is to add compounds containing transition elements such as gold, copper, and chromium. For our samples, EDX spectrometry data revealed existing fractions of iron, copper, zinc, and chromium in ascending order. Thus, copper was selectively studied by XAS as being potentially responsible for the red color in the glass beads. K-shell X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) of copper were recorded in fluorescence mode using an advanced 13-element germanium detector. Comparisons with XANES spectra of reference compounds identified two major forms of copper, monovalent copper and a metallic cluster, dispersed in the glass matrix. The cluster dimension was approximated on the basis of structural modeling and a theoretical XANES calculation. As a complement, EXAFS spectra were analyzed to determine the first-shell coordination around copper. XAS was proven to be an outstanding, advanced technique that can be applied to study nondestructively archaeological objects to understand their characteristics and how they were produced in ancient times.