Through structural relaxation, the configuration of a viscous liquid changes to allow the Gibbs free energy to be minimum
in response to temperature variations. In this review, the practical importance of relaxation in silicate melts is first illustrated
by configurational heat capacity and entropy and their connection with viscosity via Adam-Gibbs theory. Relaxation effects
on thermal expansion and compressibility are then examined, and the similarity of the kinetics of structural, enthalpy and
volume relaxation is pointed out. Turning to microscopic mechanisms, we finally stress the importance of Si-O bond exchange
and its decoupling with the motion of network-modifying elements near the glass transition.
The excess molar enthalpy of ternary mixture for 3-diethylaminopropylamine+heptane+cyclohexane were measured using a Calvet
microcalorimeter at 303.15 K.
Empirical equations, Redlich-Kister, Tsao-Smith, and Kohler and group contribution models, UNIFAC (modified version) and DISQUAC
have been applied. A reasonable representation of ternary data is obtained.
Calorimetric enthalpy changes in reactions have been measured for the formation of zinc and cadmium trimethylenediaminetetraacetates
at 298.15 K and ionic strengths of 0.1. 0.5, 1.0 mol L−1 (KNO3). The standard thermodynamic parameters of the reactions studied were evaluated from calorimetric and potentiometric measurements
under the same conditions. The results obtained were compared with the corresponding data on related compounds.
Reaction enthalpy changes were measured with the use of calorimetric method for the protonation and neutralization of glycyl-β-alanine
at 298.15 K and ionic strengths 0.5, 1.0, 1.5 mol L−1 (KNO3), and the corresponding standard thermodynamic parameters were evaluated. The results obtained were compared with the literature
data on related compounds.
Three samples of silicon dioxide were syhthesized and their surface areas were measured. A thermo-chemical cycle was designed
to calculate the molar formation enthalpy. The molar formation enthalpy, ΔfHmΦ, for three amorphous silica with the Langmuir surface area 198.0854, 25.1108 and 11.9821 m2 g−1 gave −895.52, −910.86 and −915.67 kJ mol−1, respectively. With the increasing surface area, the values of ΔfHmΦ increased accordingly.
The results suggest that the silica with larger surface area is more unstable. The wetting heat was also measured by adding
the silica powder into water. With the rehydration of the more SiOH groups on the surface, the larger surface areas of silica
lead to the more wetting heat. A smaller particle has the more unstable hydroxyl groups and surface energy.
The enthalpies of absorption and solubility at T=298.15 K of carbon dioxide in aqueous solutions of bis-(3-dimethylaminopropyl)amine (CAS RN: [6711-48-4]) are reported in
this paper. It was observed that the saturation loading of the CO2 is α=2.9 mol CO2/mol TMBPA, which is close to the theoretical value, α0=3 mol CO2/mol TMBPA. The molar heat of absorption of CO2 is independent of the polyamine concentration of the solutions and the amount of CO2 absorbed and was calculated to be ΔabsHm=–44 (2) kJ mol–1 CO2.
Authors:I. Bylina, L. Trevani, S. Mojumdar, P. Tremaine, and V. Papangelakis
A calorimetric method for determining the enthalpy of the aqueous oxidation of sulfide minerals at high temperatures and oxygen
pressures has been developed and evaluated under conditions relevant to industrial pressure oxidation operations. This information
is important for heat balance calculation and optimization of the pressure reactor design. Experiments were carried out on
a differential scanning calorimeter (DSC) with a commercial mixing cell. Enthalpy measured during oxidative dissolution of
pyrite (Valdenegrillos, Spain), pentlandite with pyrrhotite (Sudbury, Ontario, Canada) and impure chalcopyrite (Victoria,
Australia) minerals at 150°C and partial oxygen pressures of 3.4 and 5.5 MPa have been performed and found to be consistent
with theoretical estimations.
Authors:R. Nomen, M. Bartra, J. Sempere, E. Serra, J. Sales, and X. Romero
Estimation methods developed over years by S. W. Benson and co-workers for calculation the thermodynamic properties of organic
compounds in the gas phase are applied to a pharmaceutical real process with all type of non-idealities. The different strategies
used to calculate the reaction enthalpy of a chemical process, in the absence of data for complex molecules, using the Benson
group additivity method are presented and also compared with the experimental value of reaction enthalpy obtained using reaction
calorimetry (Mettler-Toledo, RC1). We demonstrate that there are some strategies that can be followed to obtain a good estimation
of the reaction enthalpy in order to begin the safety assessment of a chemical reaction. This work is part of an industrial
project  in which the main objective was the risk assessment of chemical real and complex processes using the commonly
available tools for the SMEs (with limited resources).
Authors:Marina Reis, Luís Moreira, Nelson Nunes, Ruben Leitão, and Filomena Martins
molecular interactions in solution. As such, they enclose valuable information that can be unraveled using QSPR techniques.
Formally, the solution enthalpy of a given solute A in a solvent S can be partitioned into three energetic contributions
The curing of composition containing epoxy bond is complicated chemical and technological process where under temperature
and pressure conditions a change of its structure occurs. The structure changes are possible to know by thermal methods as
DSC, DTA, etc. and also by measurement of dielectrical response under the low frequency electrical field.