Organic and Elemental Composition of Fire Residue in Surungur Archaeological Site with Assessment Fuel Type Used

Современные археологические исследования проводятся с использованием большого спектра методов естественнонаучных дисциплин. При изучении кострищ хорошо себя зарекомендовали физико-химические методы анализа, которые позволяют выйти на уровень реконструкции использовавшихся типов топлива. В данной работе приводятся результаты апробирования новой комплексной методологии изучения кострищ периода голоцена с памятника Сурунгур (Южный Кыргызстан, Ферганская долина) методами газовой хромато-масс-спектрометрии (ГХ/МС) и рентгенофлуоресцентного анализа (РФА). Установлено, что посредством ГХ/МС в пепловых прослоях сохраняются биомаркеры недогоревших остатков органического топлива (алканы, алканолы). Элементный анализ методом РФА позволяет определить распределение элементов, имеющих зольное происхождение, что также используется для оценки типа топлива. Применение нового алгоритма исследований позволило скорректировать полученные ранее результаты и установить, что в период обживания стоянки Сурунгур в качестве топлива использовалось преимущественно дерево и травыModern archaeological research is carried out using a wide range of natural science methods. When studying fires, physicochemical methods of analysis have proven themselves well, which allow us to reach the level of reconstruction of the fuel types used. This paper presents the results of approbation a new comprehensive methodology for studying Holocene fires from the Surungursite (southern Kyrgyzstan, Ferghana Valley) using gas chromatography-mass spectrometry (GC/MS) and X‑ray fluorescence analysis (XFA). It is established that by means of GC/MS biomarkers of unburned organic fuel residues (alkanes, alkanols) are preserved in the ash layers. Elemental analysis by the XFA method allows determining the distribution of elements having ash origin, which is also used to assess the type of fuel. The use of a new research algorithm allowed us to correct the previously obtained results and establish that during the Surungursite occupation, wood and grass were mainly used as fue

Polyoxoanions assembled by the condensation of vanadate, tungstate and selenite: solution studies and crystal structures of the mixed metal derivatives (NMe 4_{4}) 2_{2} Na 2_{2} [WVI^{VI} 4_{4} V V^{V} 2_{2} O 19_{19} ]·8H2_{2}O and (NMe4_{4} )4.83_{4.83} [(SeIV^{IV}WVI^{VI}4.57_{4.57} VV^{V}4.43_{4.43}O33_{33})2_{2} (WVI^{VI}(O)(H2_{2}O))(V V^{V}O) 2.6_{2.6} ]·10.57H2_{2}O

The reaction of acidified aqueous solutions of Na2WO4, NaVO3 and SeO2 in a 16 : 4 : 3 molar ratio gives a complex mixture of polyoxometalates (POMs) with both WVI and VV addenda, formulated as [(SeIVWVIxVV9−xO33)2(WVIO(H2O))(VO)m]n− with x = 4, 5, 6; m = 2 or 3. In solution, the sandwich-type complexes [(SeIVWVIxVV9−xO33)2(WVIO(H2O))(VO)m]n− slowly lose Se and convert into [WVI4VV2O19]4− and further to [WVI5VVO19]3− with a Lindqvist-type structure. These transformations were monitored with 51V and 77Se NMR, electrospray mass-spectrometry and capillary electrophoresis. Crystals of (NMe4)2Na2[(W4V2)O19]·8H2O (1) and (NMe4)4.83[(SeW4.57V4.43O33)2(W(O)(H2O))(VO)2.6]·10.57H2O (2) were isolated and structurally characterized

Synthesis and Characterization of [(OH)TeNb₅O₁₈]^6– in Water Solution, Comparison with [Nb₆O₁₉]^8–

Reaction of [Nb₆O₁₉]^8– with H₆TeO₆ in water gives telluropentaniobate [(OH)­Te­Nb₅O₁₈]^6– (<b>1</b>) as single product, which was isolated as Na⁺ and mixed Na⁺/K⁺ salts. Crystal structures were determined for Na₆[(OH)­TeNb₅O₁₈]·15H₂O (<b>Na</b>_<b>6</b><b>-1</b>) and K₆Na­[Nb_5.5­{Te­(OH)}_0.5O_18.5]·26H₂O (<b>K</b>_<b>6</b><b>Na-1</b>). Formation of <b>1</b> was monitored with electrospray ionization mass spectrometry (ESI-MS) and ¹²⁵Te NMR techniques. Capillary electrophoresis was used to calculate electrophoretic mobilities and radii of the anionic species in solutions of [(OH)­Te­Nb₅O₁₈]^6– and [Nb₆O₁₉]^8– in borate buffer. No condensation or degradation products were detected. Reactions of <b>1</b> with {Cp*Rh}²⁺ sources gives 1:1 and 2:1 hybrid polyoxometalate, which are present in solution as a mixture of isomers, as detected by ¹²⁵Te NMR. The isomerism is related to various possibilities of coordination of {Cp*Rh}²⁺ to different {M₃O₃} faces, relative to the unique Te atom. According to ESI-MS experiments in water and methanol, rapid redistribution of the organometallic fragments between the 1:1 and 2:1 complexes takes place. The 1:1 complexes are more stable in water, while 2:1 complexes dominate in methanol. X-ray structural analysis of the crystals isolated from 2:1 reaction mixture allowed identification of Na₃[{Cp*Rh}₂­TeNb₅O₁₉]·24H₂O (<b>Cp*</b>_<b>2</b><b>Rh</b>_<b>2</b><b>-1</b>) with two {Cp*Rh}²⁺ fragments capping the opposing faces of the Lindqvist anion