THERMAL-STABILITY OF POTASSIUM CARBONATE NEAR ITS MELTING-POINT

The behavior of potassium carbonate was studied by thermal analysis ne ar its melting point under 1 atm total pressure. Literature data are s cant regarding the degree to which K2CO3 decomposes in sub- and pro-li quidus thermal environments, and reliable thermodynamic data are not a vailable for the reaction K(2)CO(3)reversible arrow K2O + CO2 in the t emperature range of interest. TGA and DTA analyses indicate that signi ficant volatilization occurs below the melting point and the logarithm of the rate of volatilization is a linear function of 1/T above the m elting point. The effect of CO2 partial pressure was highly significan t in reducing, but not eliminating, volatilization near the melting po int. Graphs of In[P-CO2 x weight loss rate] vs. (1/T) were linear, sup porting a decomposition model rather than congruent volatilization. Th e melting point of K2CO3, as measured by DTA, is 905 degrees C in CO2 and 900 degrees C in N-2. (C) 1998 Elsevier Science B.V.