Thermal treatment of whewellite-a thermal analysis and Raman spectroscopic study
Thermal transformations of natural calcium oxalate monohydrate known in mineralogy as whewellite have been undertaken using a combination of thermal analysis and Raman microscopy with the use of a thermal stage. High resolution thermogravimetry shows that three mass loss steps occur at 162, 479 and 684 degrees Celsius.
Evolved gas mass spectrometry shows that water is evolved in the first step and carbon dioxide in the second and third mass loss steps. The changes in the molecular structure of whewellite can be followed by the use of the in-situ Raman spectroscopy of whewellite at the elevated temperatures. The whewellite is stable up to around 161 degrees Celsius, above which temperature the anhydrous calcium oxalate is formed. At 479 degrees Celsius, the oxalate transforms to calcium carbonate with loss of carbon dioxide. Above 684 degrees Celsius, calcium oxide is formed.
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|Item Type:||Journal Article|
|Keywords:||oxalate, whewellite, weddellite, glushinskite, Raman spectroscopy, thermogravimetry|
|Subjects:||Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > INORGANIC CHEMISTRY (030200)|
|Divisions:||Past > QUT Faculties & Divisions > Faculty of Science and Technology|
|Copyright Owner:||Copyright 2004 Elsevier|
|Copyright Statement:||Reproduced in accordance with the copyright policy of the publisher.|
|Deposited On:||14 Mar 2005|
|Last Modified:||29 Feb 2012 23:08|
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