Mechanism of thermal decomposition of anhydrous metal nitrates

In the previous paper (Jackson et al., Spectrochim. Acta Part B, 50 (1995) 1423), the gas phase products of the thermal decomposition of anhydrous Ag, Cd and Pb nitrates have been measured by means of quadrupole mass spectrometry. These results are used in this paper to distinguish between two alternative mechanisms for this process, the universally recognized condensation mechanism involving direct production of the solid metal (Ag) or oxide (CdO and PbO) through recrystallization, and the recently proposed gasification mechanism (B.V. L'vov, Mikrochim. Acta II (1991) 299) that includes a primary stage of complete gasification of all decomposition products. Quantitative analysis of the yield of volatile (NO2 and NO) and non-volatile (M, MO and MNO(3)) products into the gas phase has shown the thermal decomposition of all nitrates to proceed in a congruent way. The kinetic parameters of the process, namely, the appearance temperature and the activation energy are in good agreement with the values of these parameters calculated for the gasification mechanism. Based on these findings, and also on a qualitative analysis of some other results, the conclusion is drawn that the thermal decomposition is governed by the gasification mechanism.