Thermische Zersetzung und Lösungskalorimetrie von Ammoniumsamariumchloriden/Thermal Decomposition and Solution Calorimetry of Ammonium Samarium Chlorides

Abstract

Abstract We determined the decomposition equilibria of ammonium samarium chlorides (NH4)2SmCl5 and NH4Sm2Cl7 by total pressure measurements and derived their thermody­ namical data from the decomposition functions. The enthalpies of formation were compared with the results of the solution calorimetry. The heats of solution of all solid phases in the system SmCl3-NH4Cl and of Sm2O3 were measured in 4n HCl. The enthalpies of formation of ammonium samarium chlorides were derived from the enthalpies of formation of SmCl3 and of NH4Cl and their heats of solution. Data by total pressure measurement ΔH°B((NH4)2SmCl5,f,298) =-407,7 ± 2,9 kcal/mol; S0((NH4)2SmCl5,f,298) = 84,0 ± 4,5 cal/K-mol; ΔH°B((NH4)Sm2Cl7,f,298) = -576,8 ± 3,4 kcal/mol; S°(NH4Sm2Cl7,f,298) = 98,1 ± 5,5 cal/K-mol. Data by solution calorimetry ΔH°B(SmCl3,f,298) = -248,1 ± 0,8 kcal/mol; ΔH°B((NH4),SmCl5,f,298) = -404 ,3 ± 1,1 kcal/mol; ΔH°B(NH4Sm9Cl7,f,298)= -572,3 ± 1,8 kcal/mol.