Phase transitions of ammonium nitrate, NH_4NO_3 were observed by the dielectric measurement (1 kc/sec?10 mc/sec) and by the differential thermal analysis. Four phase changes were confirmed between-100℃ and 130℃. Some of them had large thermal hysteresis. We did not observe the phase transition at -60.4℃ as previous worker reported. A large and sharp peak was observed on some specimens at 41℃ on heating, which was probably due to the small quantity of water adsorbed on its surface. This peak was never observed on cooling.
Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy 11 418-421, 1959