The (solid + liquid) phase equilibria of triethanolamine hydrochloride ([HTEA]Cl) ionic liquid and aqueous hydrochloric acid solutions with concentrations from (0 to 8.37) mol.kg(-1) were determined by a dynamic method within the temperature range of (285.70 to 344.65) K. Solubilities of [HTEA]Cl were found to increase with increasing temperature for all the investigated solutions. However, solubilities of [HTEA]Cl in aqueous hydrochloric acid decrease with the increment of the concentration of the acid due to the common ion effect. K-SP Values of [HTEA]Cl were obtained by use of the solubility data of [HTEA]Cl in water. The modified Apelblat equation was used successfully to correlate experimental data of solubilities in hydrochloric acid. Molar dissolution enthalpy Delta//(Sol) of [HTEA]Cl in hydrochloric acid solutions was determined with the newly obtained Apelblat equation parameters.