X-ray diffraction / Powder diffraction structure analysis / Single crystal analysis / Barium dicarboxylates Abstract. Structures of new barium dicarboxylates (salts of glutaric, adipic, pimelic, suberic, azelaic and dodecanedioic acids {1-6}) were characterized. Structure solution from powder data was performed in the cases of barium adipate {2}, pimelate monohydrate {3} and dodecanedioate {6}. Structures of barium glutarate pentahydrate {1}, suberate {4} and azelate {5} were obtained from single crystal analysis.Even though these compounds are salts of homologus series of dicarboxylic acids [HOOC--C n H 2n --COOH; n ¼ (3-10)], the obtained materials are characterized by broad structural diversity. The synthesized salts form layered (2D) or three-dimensional (3D) structures. Coordination polyhedra of BaO n(8 or 9) -create layers or linear systems of polyhedra connected by edges or edges and vertices, or layers formed by isolated polyhedra linked by carboxylic acids. The degree of hydratation ranges from 5 to 0; the obtained materials crystallize in various crystallographic systems, from triclinic to tetragonal.
Laboratory X-ray powder diffraction was applied to investigate the pigments used by medieval artists in Ruthenian-Byzantine frescoes in the royal Wawel Cathedral in Krakow (Poland). It was found that red fragments contained cinnabar (PDF 06-0256), yellow contained goethite (PDF 29-0713), and blue pieces contained azurite (PDF 02-0153). The green pigment, quite difficult to identify, was finally established as green earths—pigments commonly used in Byzantine wall paintings. Calcite (PDF 24-0027) was detected in all the samples. Small amounts of quartz (PDF 46-1045) in the plaster samples were also detected. The absence or presence of only minute amounts of quartz is a characteristic feature of the Ruthenian-Byzantine frescoes. Malachite was not detected in the green parts of the frescoes, in contrast to earlier investigations of wall paintings in Poland. Experimental details and the results obtained in this study are described and discussed.
sepiolite ideal composition for two of them, which origin was from two thick (>1m) high grade sepiolite layer in Vicálvaro and Barajas (Table). Specimens sampled from less developed sepiolite layers showed a slight excess in F, Si and lower Mg occupation than ideal sepiolite [4]. It is observed a correlation between the high fl uorine content and low magnesium occupation of the studied samples with the loss of ideal structure. Sample Corrected Formulae TS4 Si 12.02 (Mg 7.97)((OH) 3.14 F 0.86) S41733 Si 12.04 (Al 0.05 Mg 7.84)((OH) 3.35 F 0.65) S4284 Si 12.17 (Al 0.03 Mg 7.63)((OH) 2.80 F 1.20) S13392 Si 12.16 (Mg 7.68)((OH) 3.04 F 0.96) Ordering and degree of occupancy of Mg and F ions are being studied in order to explain the structural anomalies found in sepiolite.
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