Conventional thermoanalytical curves provide little information on the thermal decomposition of Ca(NO3)2 · CO(NH2)2 · 3 H2O. In contrast from quasi-isothermal-quasi-isobaric thermogravimetric curves the mechanism can easily be interpreted. After the complex melts at 60°C, the solution formed is weight constant up to 135°C in the labyrinth crucible. The solution begins to boil at 135°C and gradually loses water, its boiling point increasing. The solution becomes saturated at 200°C. Thereafter, Ca(NO3)2 · CO(NH2)2 separates out while the boiling point does not change. After the departure of the water, the CO(NH2)2 immediately decomposes and Ca(NO3)2 remains.