Dragendorff reagent

Solution 1: dissolve 0.85g of basic bismuth nitrate in 10 ml acetic acid and 40 ml water.
Solution 2: dissolve 8 g of potassium iodide in 20 ml water.
Mix 5 ml of Solution 1; 5 ml of Solution 2; 20 ml of acetic acid; and 100 ml of water before use.