Potassium Iodobismuthate Solution R2

Suspend 1.7 g of bismuth oxynitrate and 20 g of (+)-tartaric acid in 40 mL of water. To the suspension add 40 mL of a 40% w/v solution of potassium iodide, stir for 1 hour and filter. This stock solution may be kept for several days protected from light. Immediately before use, mix 5 mL of the stock solution with 15 mL of water.