Thermal decomposition of [Co(NH3)6]2(C2O4)3·4H2O: II. Identification of the gaseous products

The main goal of the presented work was to verify the previously assumed decomposition stages of [Co(NH3)6]2(C2O4)3·4H2O (HACOT) [Thermochim. Acta 354 (2000) 45] under different atmospheres (inert, oxidising and reducing). The gaseous products of the decomposition were qualitatively and quantitatively analysed by mass spectrometry (MS) and Fourier-transformed infrared spectroscopy (FT-IR). It was confirmed that the gaseous products of HACOT decomposition under studied atmospheres there were H2O (stage I) and NH3, CO2 (stage II). The main gaseous products in the third stage in argon and hydrogen (20 vol.% H2/Ar) were CO and CO2, whereas in air (20 vol.% O2/Ar) only CO2 was identified. Under the oxidising as well as reducing atmospheres the influence of secondary reactions on the composition of both, solid and gaseous products was found particularly strong during the third stage of the process. The studies of the multistage decomposition of HACOT, additionally complicated by many secondary reactions, required application of the hyphenated TA–MS or TA–FT-IR techniques combined with the pulse thermal analysis PTA® allowing quantification of the spectroscopic signals and investigation of gas–solid and gas–gas reactions in situ.