Aq. solns. of NH4NO3, urea and NH4, K and Na thiosulfates as well as their mixts. were studied by thermogravimetry and differential thermal anal. to det. the mass loss and exothermal effects at elevated temp. (up to 500 degrees C). (NH4)(2)S2O3 showed the lowest thermal stability. Addn. of urea resulted in increasing the thermal stability of the soln. of NH4NO3 hazard during storage of the liq. NH4NO3-contg. fertilizers was obsd.