Physical Transitions of the Alkali Metal Nitrates as Revealed by Differential Thermal Analysis

Abstract

DIFFERENTIAL thermal analysis experiments have been carried out on the alkali metal nitrates, lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate and caesium nitrate. These experiments were conducted in air at the nominal heating rate of 10° C/min. Differential thermal analysis curves of the alkali metal nitrates were previously reported1; however, the use of smaller sample masses, bare thermocouples and the different thermocouple location and arrangement used in the present work considerably improved the resolution of the differential thermal analysis curves. This was also found to be true in the case of potassium perchlorate2. The results of the nitrate experiments are shown in Figs. 1, 2, 3, 4 and 5. Generally, the essential features of the curves for lithium, sodium and caesium nitrates are in agreement with previous work1. In the case of potassium nitrate a slight exothermal rise was reported to occur immediately prior to fusion1. This is not observed in our work as may be seen in Fig. 3.