Barium Periodides

By heating iodine with barium iodide, barium periodides similar to the calcium and strontium periodides can be obtained. Freezing-point determinations, as well as distribution experiments, indicate their presence in solution. Herz and Bulla found that for a concentration of barium iodide of 0.1054 grm.-mol. per litre, and additional iodine 0.001683 to 0.01099 grm.-mol., the dissociation constant, assuming that only the tetra-iodide is formed, is about 0.0007 at 25° C. Jakowkin considered that the compound BaI₆ is probably formed, and in nitrobenzene solution indications of the existence of the compound BaI₁₈ have been obtained. According to recent investigations, each ion of the iodide is equally active in combining with molecules of iodine, hence in dilute solutions unsaturated with iodine, Ba(I₃)₂ appears to be the only polyiodide present. In more concentrated solutions the penta-iodide is also present.