The thermodynamic investigation of the Ti-H system (TiHx; 0, x, 1.7) was conducted in the LiBr-KBr-CsBr-LiH melt at 523-673 K by utilizing the electrochemical Ti-H/H- reaction. Electrode potential-concentration isotherms were accurately obtained in which the obtained phase boundaries were consistent with the reported values. Thermodynamic quantities, such as relative partial molar Gibbs energies of absorbed hydrogen, relative partial molar enthalpies of absorbed hydrogen, and integral Gibbs energies of formation of TiH2, were also estimated. Since the obtained values agreed well with reported values, the validity of this electrochemical technique at medium-range temperatures (500-600 K) has been confirmed. (C) 2003 The Electrochemical Society.