A thermodynamic study of the equilibrium phase assemblages AgBi3S5-Bi2S3-S/Bi was made by an EMF-technique. The ternary phase was synthesized from the pure Ag2S and Bi2S3 in an evacuated silica ampoule, and ground into powder before mixing with appropriate compositions of Bi2S3 and S or Bi. The phase mixtures were pressed into different pellets, in a series of experiments. Together with pieces of pure Ag-foil and the electrolytic pellets of superionic conductor RbAg4I5 or Agl, the pellets were assembled to form the galvanic cells Pt(-)vertical bar Ag vertical bar RbAg4I5 vertical bar AgBi3S5 + Bi2S3 + S + (C) vertical bar Pt(+) and Pt(-)vertical bar Ag vertical bar AgI vertical bar AgBi3S5 + Bi2S3 + Bi vertical bar C vertical bar Pt(+). The EMF-measurements were made in a temperature range 299.15-594.15 K. In this paper, the thermodynamic functions for the formation of pavonite (AgBi3S5) at sulfur and bismuth saturation have been determined. The obtained results are in agreement with some of the available literature values. Furthermore, new experimental thermodynamic data of bismuth-saturated pavonite (AgBi3+xS5; 0 < x < 0.14), in the temperature range 299.15-594.15 K, were determined. (C) 2013 Elsevier B.V. All rights reserved.