video tutorial Prepare solid iodine (with James Earl Jones)
Goal: synthesize solid iodine by oxidizing iodide with ammonium persulfate, yielding crystalline iodine.
Method (high level): dissolve potassium iodide in water and ammonium persulfate in water; slowly combine with stirring to generate iodine, which initially stays in solution and then precipitates as crystals as more iodide is oxidized; the mixture heats up; cool with ice to promote crystallization; separate the solid and rinse, repeating until the liquid remains pale.
Purification and yield: vacuum filter and dry the product; typical final yield is around 34 g from ~50 g KI (about 90%), with potential improvement from careful washing and decanting.
Alternative: reaction with sodium bromide and ammonium persulfate is possible but slower; overheating can cause bromine separation.
Safety: iodine stains; keep a sodium thiosulfate solution ready to mop up spills.
