A method has been purposed to calculate some of the thermodynamic quantities for the thermal deformation of a smectite without
using any basic thermodynamic data. The Hançılı (Keskin, Ankara, Turkey) bentonite containing a smectite of 88% by volume
was taken as material. Thermogravimetric (TG) and differential thermal analysis (DTA) curves of the sample were obtained.
Bentonite samples were heated at various temperatures between 25–900°C for the sufficient time (2 h) until to establish the
thermal deformation equilibrium.
Cation-exchange capacity (CEC) of heated samples was determined by using the methylene blue standard method. The CEC was used
as a variable of the equilibrium. An arbitrary equilibrium constant (Ka) was defined similar to chemical equilibrium constant and calculated for each temperature by using the corresponding CEC-value.
The arbitrary changes in Gibbs energy (ΔGa0) were calculated from Ka-values. The real change in enthalpy (ΔH0) and entropy (ΔS0) was calculated from the slopes of the lnK vs. 1/T and ΔG vs. T plots, respectively. The real changes in Gibbs energy (ΔG0) and real equilibrium constant (K) were calculated by using the ΔH0 and ΔS0 values. The results at the two different temperature intervals are summarized as below: ΔG10=ΔH10−ΔS10T=−RTlnK1=47000−53t, (200–450°C), and ΔG20=ΔH20-ΔS20T=−RTlnK2=132000−164T, (500–800°C).
Authors:P. Gauden, G. Rychlicki, A. Terzyk, and R. Wojsz
A new adsorption isotherm equation based on the extension of the potential theory of adsorption on microporous fractal solids
and corresponding thermodynamic functions were formulated and applied for description of the experimental data of adsorption
on a microporous carbon. The comparison of the obtained results with the original Dubinin-Astakhov equation is presented.
In this paper the dependence of thermodynamic functions (the differential molar enthalpy of adsorption ΔH and the differential
molar entropy of adsorption ΔS) on the fractal dimension D are discussed, as well.
/Δ r G ranged from 0.20 to 1.14. These differences are not trivial and are of great importance when considering the thermodynamics accompanying the “origin of life” as it is thought to occur under anaerobic conditions
Authors:N. Manin, A. Fini, A. Manin, and G. Perlovich
Enthalpies of solution and dilution of aqueous solutions of sodium diclofenac salt were measured by isoperibolic calorimeter
at 293.15, 298.15, 303.15, 308.15 and 318.15 K. The concentration of the electrolyte was restricted to solubility salt at
various temperatures and did not exceed 0.035–0.057 mol kg−1 values depending on the studied temperature. The virial coefficients were derived from Pitzer’s model and the excess thermodynamic
functions of both the solution and the components of the solution were calculated. The analysis of thermodynamic characteristics
of the solution from concentration and temperatures was carried out and discussed.
Authors:C. Giancola, A. Buono, G. Barone, L. De Napoli, D. Montesarchio, D. Palomba, and G. Piccialli
In this work we report a thermodynamic characterization of stability and melting behaviour of two 24-mer DNA triplexes. The
third strand, that binds the Watson-Crick double helix with Hoogsteen hydrogen bonds, contains 3′-3′ phosphodiester junction
that determines the polarity inversion. The target double helix is composed of adjacent and alternate fragments of oligopurine-oligopyrimidine
tracts. The two helices differ from the substitution of the cytosine, involved in the junction, with the thymine. Calorimetric
data reported here provide a quantitative measure of the influence of pH and base modification on the stability of a DNA triplex.
A theoretical description of the proton dissociation process of weak polyacids is given. Incorporation of conformational variability in the free energy of a polyelectrolyte system provides quantitative fitting of experimental data. In addition, it extends the validity of the theory to cases in which a cooperative order-disorder transition takes place. Biopolymers considered are: poly(L-aspartic acid), poly(L-glutamic acid), samples of poly(uronic acid) and some carboxylic derivatives of a gelling bacterial polysaccharide.