Study on the system of Titanium and Iodine

The reaction between metallic titanium and elemental iodine was measured by means of a glass membrane apparatus and was confirmed that the reaction begins from ca. 130℃ to form titanium tetraiodide, and its vapor pressure was measured and thermodynamic functions for the evaporation of TiI_4 were calculated from the measurements. The reaction between metallic titanium and its tetraiodide was measured by means of a quartz membrane apparatus and the mechanism of the reaction was discussed : TiI_2 was first formed from ca. 400℃, which further reacted with TiI_4 to form TiI_3,when TiI_4 was present in excess below the temperature of ca. 300℃. When metallic titanium was present in excess, TiI_2 (s) was further reduced to form TiI (s). The presence of TiI (s) was postulated in this report for the first time. Titanium iodides of lower valencies were shown to disproportionate according to the following reactions : (a) 2TiI_3(s)=TiI_2(s)+TiI_4(g), (b) 3TiI_2(s)=2TiI(s)+TiI_4(g), (c) 4TiI(s)=3Ti(s)+TiI_4(g). The thermodynamic functions of the above reactions were also obtained from the measurements.