Thermodynamics of solution of histidine

The enthalpies of solution of l-histidine in water at 288.15-318.15 K and 0.003-0.15 mol kg⁻¹ were measured. The enthalpies of solution were found to be independent of the solute molality up to ∼0.1 mol kg⁻¹. Standard enthalpies and heat capacities of solution were computed. Free energies and entropies of solution have been estimated in the temperature range studied using literature solubility data and the results of the present study. The temperature increase was found to result in a pronounced rise of the l-histidine solubility due to the significant increase of the TΔS values. The characteristic temperatures for the thermodynamic properties of histidine aqueous solutions were estimated.