One either uses a magnetic stirrer or a metal stirring rod to ensure that the potassium iodide dissolves completely in water. But the water has to be distilled water & not tap water.
Lugol's solution is used as disinfectant & antiseptic for wounds in medicine. It is also used for the detection of starch. One will observe a color change into blue if a drop of this solution contacts a little sample of a food containing starch. The blue color is due to a complex formed between iodine & starch.