The decomposition of [Co(en)3]Cl3・3T2O over a period of 5 months was studied by infrared spectroscopy. The spectrum changed drastically with the disappearance of the bands due to ethylenediamine and the appearance of some new bands. The decomposition process of en → 2NH3+HCCH was analyzed using two models regarding the concentration of T2O. These reveal that about one thousand ethylenediamines decompose due to one β particle in the initial state
