Search Results

You are looking at 1 - 10 of 95 items

  • Author: H. Oppermann x
Clear All Modify Search
Praktische Anweisung zu deren Einrichtung und Gründung

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.

Abstract

The thermodynamical data of ammonium neodymium chlorides (NH4)2NdCl5 and NH4Nd2Cl7 were derived by the determination of their decomposition equilibria by total pres­sure measurements. Moreover, solution calorimetry was applied. The enthalpies of formation of these phases were calculated from their heats of solution and from the enthalpies of formation and the heats of solution of NdCl3 and NH4Cl.

Data by total pressure measurement:

ΔH°B((NH4)2NdCl5,f,298) = - 412,5 ± 3,6 kcal/mol;

S°((NH4)2NdCl5 f 298) = 80,1 ± 5,8 cal/K · mol;

ΔH°B(NH4Nd2Cl7,f,298) = -579,5 ± 3,5 kcal/mol;

S°(NH4Nd2Cl7,f,298) 101,8 ± 5,6 cal/K mol.

Data by solution calorimetry:

ΔH°B(NdCl3,f,298) = -251,2 ± 0,7 kcal/mol;

ΔH°B((NH4)2NdCl5,f,298) = -405,5 ± 1,0 kcal/mol;

ΔH°B(NH4Nd2Cl7,f, 298) = -576,8 ± 1,7 kcal/mol.

The phase diagram of the pseudobinary sytem Bi2Te3/BiBr3 was investigated by DTA, total pressure measurements and X-ray phase analysis. Only BiTeBr exists as a ternary phase in this system. The compound melts congruently at 526 °C. The heat of formation and standard entropy were calculated from vapor pressure data:

ΔH(BiTeBr, f, 298) = (-30,4 ± 1,4) kcal/mol; S°(BiTeBr, f, 298) = (36,2 ± 2,9) cal/K·mol.

Abstract

The decomposition equilibria of Ammonium Lanthanum Halides (NH4)2LaX5 were determined by total pressure measurements in a membrane zero manometer. The phases (NH4)2LaX5 decompose in one step to give solid LaX3 and gaseous NH3 and HX. From the decomposition functions the enthalpies of formation and the standard entropies of the phases are derived.

ΔH°B (NH4)2LaCl5,f,298) = -411 ,7 ± 2,2 kcal/mol; S°((NH4)2LaCl5,f,298) = 86,7 ± 2,3cal/Kmol;

ΔH°B (NH4)2LaBr5,f,298) = -351,6 ± 3,8 kcal/mol; S°((NH4)2LaBr5,f,298) = 101,1 ± 1,8 cal/Kmol;

ΔH°B (NH4)2LaI5,f,298)= -268 ,9 ± 3,9 kcal/mol; S°((NH4)2LaI5,f,298) = 115,5 ± 4,3 cal/Kmol.

The heterogeneous reactions:

OsO4,s =OsO4,g, 2OsO2,s = Oss + OsO4,g, Oss + 3OsO4,g = 4OsO3,g, OsO2,s + OsO4,g = 2OsO3,g and the homogeneous reaction OsO4,g = OsO3,g + 1/2 O2,g were determined by total pressure measurements. From this and from chemical transport reactions of OsO2 and Os with Osmium tetroxide, the enthalpy of formation of gaseous OsO3 was computed to ΔH°B(OsO3,g,298) = -40,0 ± 3 kcal/mol.