Authors:A. A. Opalovsky, V. E. Fedorov, and T. D. Fedotova
The thermal stability and non-isothermal kinetics of the decomposition of alkali metal bifluorides were studied using a derivatograph. The removal of hydrogen fluoride from LiF · HF and NaF · HF takes place before melting and their decomposition occurs in a single stage; however, potassium, rubidium and cesium bifluorides at first undergo polymorphous transformation and melting on heating, and their decomposition proceeds stepwise. The thermal stability of alkali metal bifluorides has been found to increase with increasing ionic radius of the cation, reflecting its correlation with the hydrogen bond strength in these compounds.
The fusion temperatures (Tf) of rare earth metal trihalides LnX3 (Ln=La−Lu, Y; X=Cl, Br, I) typically decrease to a minimum, before taking on an upward trend as the ionic radius of Ln3+ decreases. This trend is associated with the variations in the energetic stability of the coordination polyhedron around Ln3+. A good correlation is obtained between the variations in the energetic stability of the crystal structure of LnX3 andTf.
The thermal decomposition of Cd3V10O28 · 16H2O and Mg3V10O28 · 18H2O has been investigated. It was found by means of IR spectroscopy and X-ray phase analysis that the final products of decomposition of the given compounds are V2O5, the corresponding metavanadates and the vanadium bronzes of cadmium and magnesium. Present and previous results allow conclusions on the thermal decomposition of decavanadates of bivalent metals.
Authors:T. Meisel, Z. Halmos, K. Seybold, and E. Pungor
The thermal decompositions of lithium, sodium, potassium, rubidium and caesium formates were investigated by a complex dynamic thermoanalytical method. The ratio of the products in reactions resulting in alkali metal carbonates and oxalates depended variously on the atmosphere used. Differences were found compared to isothermal investigations, in that the catalytic effects of bases could not be observed and the oxalate-conversion was lower. The formation of oxalate did not occur in the cases of lithium and caesium formates; the order for the other salts was sodium formate < potassium formate > rubidium formate.
Authors:R. K. Verma, L. Verma, M. Chandra, and A. Bhushan
Summary A comparative study of the non-isothermal decomposition of the dl-lactate hydrates of magnesium, calcium and strontium has been made with that of the dl-lactate hydrates chromium(III), manganese(II), iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) keeping dry air as the purge gas and the heating rate maintained at 10 K min-1. While the dl-lactates of manganese(II), cobalt(II) and copper(II) followed single step decomposition scheme suggesting that dehydration and decomposition steps overlapped, the dehydration steps of the other compounds were distinct. &-T plots of none of the dehydration steps showed any induction period, indicating no physical desorption, nucleation or branching. Neither the & max-values nor the onset temperatures of the dehydration steps did show any pattern. The TG data of the dehydration steps have also been analyzed using the Freeman-Carroll, Horowitz-Metzger, Coats-Redfern, Zsakó, Fuoss-Salyer-Wilson and Karkhanavala-Dharwadkar methods. Values of order of reaction, activation energy and Arrhenius factor have been approximated and compared. There are similarities in the activation energy values for the dehydration steps (< 60 kJ mol-1 in general). It is higher with group 2 metals and lower in transition metals (maximum in magnesium and lowest in chromium and iron lactates). In cases of overlapping of dehydration and decomposition steps, the activation energy values are on the lower side with the same trend (lower in cobalt and copper cases).
Authors:Andreza Ribeiro, Ana Figueiredo, Regina Ticianelli, Georges Nammoura-Neto, Natália Silva, Mauricio Kakazu, and Guilherme Zahn
São Paulo is the largest city in Brazil and South America with about 20 million inhabitants in the metropolitan area, more
than nine million motor vehicles and intense industrial activity, which are responsible for increasing pollution in the region.
Nevertheless, little is known concerning metal and semi-metal content in the soils of this metropolitan region. This type
of information could be extremely useful as a fingerprint of environmental pollution. The present study determined the elements
As, Ba, Co, Cr, Sb, and Zn concentrations in soils adjacent to avenues of highly dense traffic in São Paulo city to assess
their levels and possible sources. The analytical technique employed was Instrumental neutron activation analysis. The results
showed, except for Co, concentration levels higher than the reference values for soils of São Paulo, according to the Environmental
Protection Agency of the State of São Paulo guidelines. When compared to similar studies in other cities around the world,
São Paulo soils presented higher levels, probably due to its high density traffic and industrial activity. The concentrations
obtained for As and Cr indicate anthropogenic origin. The high levels of the traffic-related elements Ba, Sb, and Zn in soils
nearby high density traffic avenues indicate they may originate from vehicular exhausts.
Hydrazine derivatives of the monobasic nitrilotriacetate salts of zinc and alkaline earth metals have been prepared. IR absorption
frequencies and thermal properties of these metal-hydrazinium nitrilotriacetates, (N2H5)M[N(CH2COO)3]·xH2O have been defined. All the three -COOH appear to be dissociated in these salts. In thermal decomposition, these salts initially
undergo dehydration followed by dehydrazination and via acetate intermediate step to metal oxycarbonates.
Authors:A. Małecki, R. Gajerski, S. Łabuś, B. Prochowska-Klisch, and K. Wojciechowski
A series of six nitrates(V) hydrates of 4d-metals as well as mercury and cadmium thermal decomposition was examined by DTA,
TG and EGA techniques. It was found that thermal decomposition of d-metals nitrate(V) hydrates proceeds in three stages: partial
dehydration, oxo-nitrates and hydroxide nitrates formation and metal oxides formation. General chemical equations for all
decomposition stages were proposed. It was found that dehydration of hydrated salts is accompanied by partial decomposition
of nitrate(V) groups.
The knowledge of quantities of alpha-active nuclides (especially Pu and Am) present in contaminated metal waste from decommissioned nuclear power plant, is very important for treatment of this metal waste by melting technology. The surface part of the analyzed metal was mechanically or electrochemically removed until bulk material was reached. The iron was removed in the form of an amalgam. Pu was separated from Am by extraction with TTA and the main contaminants of the metal surface were determined after counting previously electrodeposited samples.
A number of reference materials for oxygen in different non-ferrous metals have been certified by BCR in the frame of a multidisciplinary
Community project. The contribution of nuclear analysis methods is illustrated by several examples concerning the optimization
of sample preparation techniques, the analysis of low and high oxygen non-ferrous metals and the extension of the program
to other non-metals, especially nitrogen and carbon.