of polymorphic forms I and II of theophylline in water at 298.15 K using the isoperibol solution calorimeter have been determined
in the range of concentration (0.311–1.547) · 10−3/mol · kg−1. The enthalpies of hydration
Authors:Luis H. Blanco, Yina P. Salamanca, and Edgar F. Vargas
, thermodynamic studies at low concentration, of less than 0.05 mol kg −1 , are scarce; in the literature, data are found for partial molar volumes at molar concentrations above 0.05 mol L −1 [ 6 ] and it is only possible to find data of enthalpiesofsolution at
Authors:J. Canotilho, F. Costa, A. Sousa, J. Redinha, and M. Leitão
Enthalpies of solution of various terfenadine samples in methanol and in ethanol were measured. Samples were prepared by crystallization in different solvents. The calorimetric results give important information on crystal structure of the terfenadine forms and on the solute/solvent interactions of this compound with the solvents.
Authors:M. Ji, J. Liu, S. Gao, B. Kang, R. Hu, and Q. Shi
The enthalpies of solution in water of RE(His)(NO3)3
H2O (RE=La—Nd, Sm—Lu, Y) were measured calorimetrically at 298.15 K, and the standard enthalpies of formation of RE(His)aq3+ (RE=La—Nd, Sm—Lu, Y) were calculated. The plot of the enthalpies of solution vs. the atomic numbers of the elements in the lanthanide series exhibits the tetrad effect.
Authors:Yang Zhao, Liang Zhao, Xing Wei, Buxing Han, and Haike Yan
The enthalpies of solution of potassium chloride (KCl) in water and magnetically treated water (magnetized water) have been
measured at 298.15 K using a LKB-8700 precision solution calorimeter. From the experimental results, it was observed that
the effect of magnetic field on the enthalpy of solution is measurable. This is probably due to the distortion of the hydrogen
bond of water resulting from magnetic treatment.
The enthalpies of solution in water of L--methionine and its zinc complexes Zn(Met)Cl2, Zn(Met)2Cl2·2H2O, Zn(Met)(NO3)2·1/2H2O, Zn(Met)3(NO3)2·H2O and Zn(Met)SO4·H2O have been measured at 298.15 K. The standard enthalpy of formation of met(aq) has been calculated. The experimental results have been discussed.
The enthalpies of solution and dilution of glycine, L-α-alanine, L-valine, L-α-leucine, L-α-serine and L-α-threonine in water
were measured at 298.15 K. The results were applied to calculate the enthalpic coefficients of homogeneous interactions between
zwitterions of L-α-amino acids in aqueous solutions.
The standard molar enthalpies of solution of glycine, L-α-alanine, L-α-valine and L-α-leucine in aqueous solutions of urea
at 298.15 K were determined by calorimetry. The results obtained were used to calculate the heterogeneous enthalpic interaction
coefficients between the zwitterions of the L-α-amino acids and a molecule of urea in water. The values of the resultant enthalpic
interaction coefficients are interpreted in terms of the effects of the hydrophobic alkyl groups on the interactions between
the zwitterions of the L-α-amino acids and a polar molecule of urea in aqueous solutions.
Authors:A. Przepiera, M. Wisniewski, W. Dabrowski, and M. Jablonski
Results of calorimetric determination of integral enthalpies of solution of some hydrates (monohydrates and heptahydrates)
of 3d transition metal sulphates such as FeSO4, NiSO4 and MnSO4 in three-component systems at sulphuric acid concentrations up to 2M are reported. Measured values of integral enthalpies of solution are the basis for calculation of activity coefficient temperature
dependences according to Pitzer's model.
The position of scandium and yttrium within lanthanides in respect to the enthalpies of solution of anhydrous rare earth halides has been discussed. It has been indicated that although the respective shift of Sc(III) as a quasi-heavy lanthanide is less pronounced than for Y(III), the overall covalency within the trivalent ions of the scandium group, Ln(III) and An(III) included, is the most pronounced for Sc(III) due to participation of the empty orbitals in bonding: Sc(III)>An(III)>Ln(III)> Y(III). The irregularity of this trend is produced by the superimposed participation of the 5f (An(III)) and, to a lesser extent, of the 4f (Ln(III)) orbitals in bonding. The crucial factor of a maximum difference between the product and substrate coordination number (CN) of the central ion for covalency, separation factor and isotope effect in chemical exchange is emphasized.