Solution Microcalorimeter for Measuring Heats of Solution of Radioactive Elements and Compounds

摘要

The microcalorimeter vessel is constructed of tantalum metal, with a nominal volume of 5 cm exp 3 . Its energy equivalent is 24 J K exp -1 when containing 5 cm exp 3 H sub 2 O. The thermal leakage modulus is 0.010 min exp -1 . A thermistor is employed as the temperature sensor. The operating sensitivity is about 1 x 10 exp -5 K (300 mu J). The performance of the calorimetry system was tested using tris(hydroxymethyl)aminomethane (TRIS) and magnesium metal. The results of the TRIS experiments, at a concentration of 1 g dm exp -3 in 0.1 N HCl at 298 K, yielded a heat of solution of -29.606 +- 0.063 kJ mol exp -1 . The magnesium experiments, in 1 N HCl at 298 K, gave a heat of solution of -465.965 +- 1.136 kJ mol exp -1 . The heat of solution of curium-248 metal in 1 N HCl at 298 K was measured. The experiments, which should not be considered definitive, yielded a heat of solution of -606.4 +- 1.8 kJ mol exp -1 . A single measurement in 6 N HCl gave a heat of solution of -602.3 kJ mol exp -1 . From these results the heat of formation of Cm exp 3+ /sub (aq)/ is calculated to be -607.2 +- 2.5 kJ mol exp -1 . (ERA citation 04:019894)