RESUMEN
This paper discusses in detail the design, construction, and performance of the vacuum jacketed, adiabatic solution calorimeter which was used for the work in the certification of two NBS Standard Reference Materials for solution calorimetry. As a test for the calorimetric precision the following enthalpies of reaction were measured (referred to the mass or moles of H 2 SO 4 · 8H 2 O): H 2 S O 4 â 8 H 2 O + 2.36 ( N a O H â 2620 H 2 O ) = ( N a 2 S O 4 â 0.36 N a O H â 6193 H 2 O ) soln Δ H r ( 298.15 K ) = - 590.692 ± 0.101 J â g - 1 = - 34 , 194.1 ± 5.9 cal â mol - 1 H 2 S O 4 â 8 H 2 O + 2.6 ( N a O H â 714 H 2 O ) = ( N a 2 S O 4 â 0.6 N a O H â 1866 H 2 O ) soln Δ H r ( 298.15 K ) = - 590.828 ± 0.193 J â g - 1 = - 34 , 203.4 ± 11.1 cal â mol - 1 .
RESUMEN
An adiabatic solution calorimeter was used to measure the enthalpies of the following reactions: BeO ( c ) + [ 96 HF + 338 H 2 O ] ( l ) â [ BeF 2 + 94 HF + 339 H 2 O ] ( l ) Δ H at 298.15 K = - 101.30 ± 0.20 kJ â mol - 1 BeO ( c ) + [ 48 HCL + 333 H 2 O ] ( l ) â [ BeCL 2 + 46 HCl + 333 H 2 O ] ( l ) Δ H at 352.58 K = - 54.19 ± 0.22 kJ â mol - 1 Δ H at 298.15 K = - 53.0 ± 2.0 kJ â mol - 1 Δ Cp is 12.5 ± 2.8 J â mol - 1 â K - 1 for the first reaction in the range 298 to 325 K. .
RESUMEN
The enthalpy of reaction of tris(hydroxymethyl)aminomethane, NBS Standard Reference Material 724a, measured in an adiabatic solution calorimeter at 298.15 K in 0.1 N HCl solution is -245.76 ±0.26 J · g-1, and in 0.0500 N NaOH solution is 141.80 ± 0.19 J · g-1. The conditions applicable and the factors included in the overall uncertainties are discussed in detail. For the reaction in 0.1 N HCl in the range, 293 to 303 K, ΔCp = 1.435 ± 0.023 J · g-1 · K-1, and in 0.0500 N NaOH in the range, 295 to 303 K, ΔCp = 1.025 ± 0.025 J · g-1 · K-1. Possible sources of error in measurements of the reactions are discussed. A summary of other enthalpy measurements of the reaction in 0.1 N HCl is given.