Lugol's iodine
Lugol's iodine, also known as Lugol's solution, first made in 1829, is a solution of iodine named after the French physician J.G.A. Lugol. Lugol's iodine solution is often used as an antiseptic and disinfectant, a starch indicator, to replenish iodine deficiency, to protect the thyroid gland from radioactive materials (e.g. "fallout"), and for emergency disinfection of drinking water.
Lugol's was often used in the treatment of gout and was used as a first line treatment for hypothyroidism in adults.
It consists of 10% iodine (I2) and 10% potassium iodide (KI) in 80% distilled water with a total iodine content of 130 mg/mL. Potassium iodide makes the iodine water soluble through the formation of the I3- ion.
It is obtained from chemists and pharmacists who are licensed to prepare and dispense the solution.
This solution is also used as an indicator to test for the presence of starches in organic compounds, with which it reacts by turning a dark-blue/black.  IKI will stain starches due to its interaction with the coil structure of the polysaccharide.  IKI solution will not detect simple sugars such as glucose or fructose. In the pathologic condition amyloidosis, amyloid deposits can be so abundant that affected organs will also stain grossly positive for the Lugol reaction for starch.
Other names for Lugol's solution are IKI (Iodine Potassium-Iodide); Iodine, Strong solution (Systemic); Aqueous Iodine Solution BP.
It can be used as a cell stain, making the cell nuclei more visible and for preserving phytoplankton samples.

# Applications
Historically, Lugol's iodine solution has been widely available and used for a number of health problems with some precautions.  Lugol's is sometimes prescribed in a variety of alternative medical treatments.
In the United States of America, Lugol's solution was previously unregulated and available over the counter as a general reagent, an antiseptic, a preservative, or as a medicament for human or veterinary application.  However, effective August 1, 2007, the DEA now regulates Lugol's solution (and, in fact, all iodine solutions containing greater than 2.2% iodine) as a List I precursor because it may potentially be used in the illicit production of methamphetamine. By contrast, Lugol's iodine solution is available over the counter in Canada and Mexico, for example.
Following the Chernobyl nuclear reactor disaster in April, 1986, Lugol's iodine solution was administered to 10.5 million children and 7 million adults in Poland as a prophylactic measure against accumulation of radioactive iodine-131 in the thyroid.
Many organs in the body require iodine to function normally, especially breast tissue. Studies have confirmed a link between fibrocystic breast disease and lack of iodine in a woman's diet. Recent studies have confirmed an increase in breast cancer since manufacturers eliminated iodine from bread approximately 20 years ago and replaced it with bromine. Bromine is toxic to the thyroid gland as well.
Lugol's iodine is sometimes used to treat thyroid storm, and may be taken pre-operatively.
Lugol's solution can also be used in various experiments to observe how a cell membrane uses osmosis and diffusion.