Application of thermo-Raman spectroscopy to study dehydration of CaSO4 center dot 2H(2)O and CaSO4 center dot 0.5H(2)O

In this work, dehydration of CaSO4. 2H(2)O and CaSO4. 0.5H(2)O in stagnant air was studied by thermo-Raman spectroscopy from 25 to 300 degrees C. The composition could be identified directly from the Raman spectra by comparin g with the known Raman spectra of CaSO4. 2H(2)O, CaSO4. 0.5H(2)O and CaSO4. Thermo-Raman spectra indicated that dehydration of CaSO4. 2H(2)O was a two step consecutive reaction and CaSO4. 0.5H(2)O was the intermediate in the experimental conditions. The band intensities illustrated the variation in the relative amount of each species. The derivatives of the band intensitie s showed the maximum rate in dehydration of that species. The shifts in ban d positions also revealed the transformation. (C) 1999 Elsevier Science S.A . All rights reserved.