Two solutions are prepared by dissolving 5.4 g of mercury(II) chloride in 100 mL of water and 7 g (excess) of potassium iodide in 50 mL of water. The solutions are combined and stirred for 5 minutes, the mixture is then filtered and washed with water. The product may be dried in open air.
HgCl2 + 2 KI = HgI2 + 2 KCl
Combining the solutions
The mixture after complete addition
The dried product