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one. Sufficient amount of information about enthalpy changes of reactions in water was accumulated for complex formation between transition metals ions and amino acids anions and glycine-ion [ 1 – 3 ] and for complex formation of glycine and

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Abstract  

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.

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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.

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The enthalpy changes of salting process of hen-egg white lysozyme in buffer acetate solutions (pH=4.25) as a function of concentration of following electrolytes: LiCl, KCl, K2SO4, Li2 SO4 and (NH4)2SO4 are determined. Obtained data according to McMillan and Mayer’s approach, has been analyzed in the terms of the enthalpic pairwise interaction coefficients: lysozyme – lysozyme h xx, and lysozyme – salt h xy. The ability of cations to precipitate lysozyme solution in relation to the concentration of cations can be seen from the series as follows: Li+> Na+>K+>NH4++

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Isothermal TG and DSC measurements were used to study the effect of the pyridine substituent (3-R) on the kinetics and enthalpy change in the thermal decomposition of Ni(NCS)2(3-R-py)4 complexes.

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The mathematical-physical equation concerning the process of calorimetry of electrode reactions was deduced, and the corresponding solutions were obtained respectively for the period of the electrochemical polarization and that of the natural cooling. The calorimetry of the anodic oxidation of ferrocyanide to ferricyanide under linear sweep-current polarization was carried out, the obtained apparent enthalpy change of the electrode reaction agreed well with that obtained by the calorimetry with constant currents. The developed calorimetry with linear sweep-current and the data processing method are applicable for quick determination of apparent enthalpy changes of electrode reactions.

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In this paper problems associated with a conventional heat-flux DSC are discussed. A single pan calorimeter has been designed and built which eliminates many of the errors that occur in a conventional DSC. It was found that: enthalpy changes and heat capacity were repeatable to better than1%; the apparent latent heat and heat capacity did not depend on specimen size or significantly on rate of heating as often occurs in a two-pan heat-flux DSC; during the melting of pure Al, more than 80% of the latent heat was evolved over a temperature of 0.04 K; in alloys, separate heat capacity peaks for different reaction less than 1 K apart were resolved.

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A capillary long neck glass sample holder is proposed for the determination of boiling temperatures of essential oils containing a majority component. Essential oils from Aniba dukei K. and Pimenta dioica L. containing linalool and eugenol, respectively, as major constituents were used after optimization of parameters such as scan rate, sample mass and starting temperature. Best performance in the determination of boiling temperatures was obtained with the proposed sample holder in comparison with commercial aluminum pans. Good agreement was obtained for the boiling temperature and enthalpy for the essential oil samples with the linalool and eugenol standards.

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At 298.15 K, the solubilization of hen ovotransferrin at buffered pH 7.8 (0.08 M Tris⋅HCl buffer, containing 0.1 M CaCl2) and the solubilization of α-chymotrypsin (from bovine pancreas) at non-buffered pH 3.0 (0.001 M HCl) both resulted in large exothermic reactions, being the apparent ΔHs –2485 in the first case and –780.1 kJ mol–1 in the second case, respectively. By contrast, the complete hydrolysis of ovotransferrin (pH 7.8) achieved by using a-chymotrypsin (pH 3.0) gave an endothermic reaction with ΔH=+31.84 kJ mol–1.

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