BÖTTCHER, M.E. & GEHLKEN, P.-L. (1996):
Dehydration of natural gaylussite (Na2Ca(CO3)2 · 5H2O) and pirssonite (Na2Ca(CO3)2 · 2H2O) as illustrated by FTIR spectroscopyv.
The FTIR spectra of natural gaylussite (Na2Ca(CO3)2 · 5H2O) and pirssonite (Na2Ca(CO3)2 · 2H2O) are reported between 4000 and 400 cm-1, and the effect of heating up to 500 ºC on the mid-infrared spectra of quenched reaction products is investigated. Upon heating, the hydrated carbonates lose their crystallisation water and transform directly to Na2Ca(CO3)2. The mid-infrared spectrum of Na2Ca(CO3)2 is reported for the first time and the absorption bands are assigned to specific vibrational modes. Under the chosen conditions, dehydration temperatures are between 60º and 90 ºC for gaylussite, and between 110º and 200 ºC for pirssonite. Gaylussite and pirssonite are heated up to 360 ºC directly or as prepared KBr pellets. Depending on the experimental conditions chosen, differences in the FTIR spectra of quenched carbonates are observed. A short Na – K exchange between (dissolved) KBr and Na2Ca (CO3)2 in a self-generated water-steam atmosphere within the prepared KBr pellets is supposed to be the reason for different FTIR spectra and formation of (Na,K)2 Ca(CO3)2 solid-solutions is suggested. No cation exchange is observed upon heating gaylussite and pirssonite dispersed in KBr pellets to temperatures below the dehydration temperature.