Thermal behaviour of hydroxides, hydroxysalts and hydrotalcites

Mass spectrometric analysis of gases evolved during thermal decomposition o f divalent metal hydroxides, hydroxysalts and hydrotalcites show that all t hese compounds undergo dehydration in the temperature range 30 < T < 220 de grees C followed by decomposition at temperatures above 250 degrees. The la tter step involves simultaneous deanation and dehydroxylation of the layers . Our observations conclusively prove that alternative mechanisms which env isage CO2 evolution due to deanation at lower temperatures proposed by Kane zaki to be wrong.