Orange Tornado

We use mercury(II) chloride solution and potassium iodide to demonstrate a precipitation reaction. Saturated potassium iodide solution is placed on a magnetic stirrer and the speed is set so that a vortex is created. Mercury(II) chloride is then added and an orange precipitate, mercury iodide, forms. This precipitate then vanishes as a further reaction occurs. Chemistry - Reactions - Learning Points. Soluble salts dissociate into ions in solution. Insoluble salts form an ionic lattice so come out of solution as precipitates. Insoluble reactants can react in solution to form soluble products. Mercury compounds are toxic and highly regulated. A Twig Experiment Film. Let students experience real experiments in lab conditions anywhere, from setup, method all the way through to analysis and real-world application.