Abstract
From the results of the vapour pressure measurements described in previous communications of this series1 and the determination of the compositions of the phases occurring in the different equilibria, the P‐T‐x space model for the binary system is derived. The P‐T and T‐x projections and the most important P‐x and T‐x sections are given. The thermodynamic constants of NbOCl3 are derived also from the results of the measurements described previously.