Preparation of bismuth oxyiodide
95.4 g powdered crystallized bismuth nitrate are dissolved in 160 ml glacial acetic acid by warming gently. At the same time, 33.2 g potassium iodide and 50 g crystallized sodium acetate are dissolved in 2 liters cold water. The solution containing potassium iodide and sodium acetate is placed in a dish and the solution containing bismuth nitrate in acetic acid is added in a very thin stream from a dropping funnel, with frequent stirring. At the point where the liquid strikes a greenish-black precipitate forms at first; upon stirring this immediately changes to a lemon color. On further addition of the bismuth solution the product assumes a dark, brick-red color. The precipitate settles very readily. It is decanted, filtered and dried at 100° C.
Laboratory manual of inorganic preparations, by H. T. Vulte, 141-142, 1895