Physicochemical characterisation of pottery from the Vinca culture, Serbia, regarding the firing temperature and decoration techniques

A study of decorated Neolithic pottery samples from the excavation site Plocnik, Serbia, was performed using X-ray powder diffraction (XRPD), Fourier transform infrared (FTIR) and X-ray fluorescence (XRF) spectroscopy. The investigated samples belong to the era of the Vinca culture that existed in the central Balkan region from the mid VI until the first half of the V millennium BCE. The mineralogical composition of the pottery samples and comparison of the investigated pottery with thermally treated local clay indicated firing temperatures in the range from 600 to 800 degrees C. Two different types of white pigments were identified in white incrusted decorations: calcium carbonate and bone white (composed of crushed bones). This is the first evidence of the use of bones for decorations in pottery of the Vinca culture from the excavation site Plocnik. In addition to this, it was revealed that the potters used the iron reduction technique for obtaining black decorations

Spectroscopic investigation of two Serbian icons painted on canvas

A multianalytical study of two Serbian icons, The Virgin and Child and St. Petka, painted on canvas by unknown authors was performed in order to identify the materials used as pigments, binders and the ground layer. The investigated icons belong to the Museum of the Serbian Orthodox Church in Belgrade. Samples, collected from different parts of the icons, were analysed by: optical microscopy (OM), energy dispersive X-Ray fluorescence (EDXRF), Fourier transform infrared (FTIR) and micro-Raman spectroscopy. The obtained results revealed the presence of the following pigments: Prussian Blue, ultramarine, Green Earth, iron oxides, Lead White and Zinc White. Linseed oil was used as the binder. The materials used for the ground layers were gypsum, calcite, baryte and Lead White. The gilded surface of the icon The Virgin and Child was made of gold. The gilded surface on the frame of this icon was made of imitation of gold, i.e., Schlagmetal, since EDXRF spectroscopy showed the presence of copper and zinc, while gold was not detected. Based on the style and the consideration of an art historian, as well as on the obtained results for the corresponding pigments and binder, both icons were most probably made at the end of 19th or the beginning of the 20th century

Infrared study of some 2-substituted-6-hydroxy-4-pyrimidine carboxylic acids. Correlation with MO-calculations

The IR spectra of a series of 2-substituted-6-hydroxy-4-pyrimidine carboxylic acids (substituent = OH, SH, CH3, CH3S and NH2) were studied from the aspect of the influence of the subsitutent on the polarizability of some bonds, keto-enol tautomerism and hydrogen bond formation. The spectra were taken using solids due to the low solubility of the acids. Theoretical calculations were done using the MNDO-AM1 semiempirical molecular-orbital method. The stabilities of various tautomers were calculated simulating the dielectric continuum using the COSMO facility of the MOPAC program package. Theoretical calculations were made for all the possible tautomers of the 2-substituted-6-hydroxy-4-pyrimidine carboxylic acids. For the most stable isomers, the vibrational spectra were calculated. For the majority of the compounds the most stable isomer was identified having the structure 2-Y-6-oxo-4-carboxy-3H-pyrimidine. Besides this structure, for the 2-amino-, and 2-methyl- derivatives the zwitterionic forms have very similar stability. The 2-hydroxy compound is most stable as the 2,6-dioxo-1H, 3H isomer. The calculated vibrations for the compounds with a single stable structure correlate very well with the experimental frequencies. For the 2-methyl- and 2-amino- compounds the correlation is considerably less satisfactory. The most probable reason for this deviation is the existence of two or more tautomets in equilibrium. The correlation of the measured frequencies and the pKa values of the acids, indicate that the same tautomers exist in the solid state and in the solution

A study of the IR spectra of the copigments of malvin chloride with organic acids

The infrared spectra of the copigments of malvin with several organic acids: caffeic, ferulic, sinapic, chlorogenic, and tannic, were analyzed in order to elucidate the bonding of the molecules in the copigments. It was established that copigmentation is realized through hydrogen bonding between malvin molecules and the acids under study. The infrared spectra reveal that two groups of hydrogen bonds are formed, which include interactions of different molecular structures: hydroxy groups (bands around 3500 cm1) and oxonium ions of the molecules (bands below 3000 cm1). The formed hydrogen bonds were found to be of different strengths. The strengths of the hydrogen bonds were tentatively correlated with thermodynamic properties of the corresponding copigmentation reactions

A study of 12-tungstosilicic and 12-molybdophosphoric acids in solution

The behaviour of two heteropolyacids (HPAs) with quite different stability in aqueous solutions was systematically investigated by UV, IR and NMR spectroscopy and potentiometric titration. It was shown that the Keggin structure of 12-tungstosilicic acid (H4SiW12O40, WSiA) anion was sustained over a wide range of pH from 1.0 to 7.0, while the same anion type of 12-molybdophosphoric acid (H3PMo12O40, MoPA) was present only at pH 1.0. This means that under physiological conditions WSiA is dominantly present in the form of a Keggin-anion, whereas the structure of MoPA is completely decomposed to molybdate and phosphate. The obtained results are of special importance for bio-medical and catalytic applications of these compounds and for a better understanding of the mechanism of their action

Archaeometric study of medieval pottery excavated at Stari (Old) Ras, Serbia

A combined study of a series of polychromatic and monochromatic glazed medieval pottery shards excavated from the archaeological area of Stari (Old) Ras in southern Serbia, including petrographic and chemical analysis, powder X-ray diffraction (PXRD) and Fourier transform infrared (FTIR) spectroscopy, allowed us to clearly distinguish between two groups of ceramics. Ras pottery, made of fine-grained well-cleaned clay and characterised by a rich mineral assemblage, was produced by firing in a temperature range between 800 and 900 degrees C. Reljina Gradina ceramics were produced at similar temperatures from materials which, with regard to mineralogical and chemical composition, show clear similarity with local clay, suggesting that these samples are of local origin and production. This work is the first systematic archaeometric study of medieval pottery excavated on the territory of Serbia

A spectroscopic investigation of 12-tungstophosphoric acid alkali salts

In this paper the latest results of our continuing investigation of heteropoly acids and their salts are reported. Specially attention was paid to the influence of cations on the dynamic equilibrium of protonic species, as well as on the structure of the host lattice itself, i.e., the Keggin anions. The investigations were done by IR and Raman spectroscopy within the range of 1200-40 cm-1