Thermal decomposition of barium oxalate hemihydrate BaC2O4·0.5H2O |
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Authors: | AH Verdonk A Broersma |
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Institution: | Department of Inorganic Chemistry, State University of Utrecht, Croesestraat 77a, Utrecht The Netherlands |
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Abstract: | The thermal behaviour of BaC2O4sd0.5H2O and BaCO3 in carbon dioxide and nitrogen atmospheres is investigated as part of a study about the thermal decomposition of barium trioxalatoaluminate. For this purpose thermogravimetry, differential thermal analysis, differential scanning calorimetry and high temperature X-ray diffraction were used. An infrared absorption spectrum of BaC2O4·0.5H2O was scanned at room temperature.At increasing temperature, in dry nitrogen, the hydrate water of BaC2O4· 0.5H2O is split off, followed by the oxalate decomposition. A part of the evolved carbon monoxide disproportionates, leaving carbon behind. At higher temperatures the latter reacts with barium carbonate, previously formed. Finally the residual solid barium carbonate decomposes into barium oxide and carbon dioxide.In dry carbon dioxide atmosphere an analogous dehydration occurs, followed by oxalate decomposition. Under these conditions the carbon formation is fully suppressed, and as a consequence no secondary reaction occurs. The barium carbonate decomposition is shifted to much higher temperatures, at a low rate in the solid phase, a strongly accelerated one at the onset of melting, and a moderated one when the melt is saturated with barium carbonate. The two phase transitions of BaCO3 are detectable in both atmospheres mentioned. |
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